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CR2.7

Process understanding is key to assessing the sensitivity of glacier systems to changing climate. Comprehensive glacier monitoring provides the base for large-scale assessment of glacier change. Glaciers are monitored on different spatio-temporal scales, from extensive seasonal mass balance studies at selected glaciers to multi-decadal repeat inventories at the scale of entire mountain ranges. Internationally coordinated glacier monitoring aims at combining in-situ measurement with remotely sensed data, and local process understanding with global coverage. This session invites studies from a variety of disciplines, from tropical to polar glaciers, addressing both in-situ and remotely sensed monitoring of glaciers, as well as uncertainty assessments.

This year we have combined session CR2.7 with CR1.6 "Glaciers and ice caps under climate change":
Mountain glaciers and ice caps are major contributors to sea-level rise and have large impacts on water balance of local basins. This is a general session on glaciers and ice caps where the relationship to climate forms a particular focus. The IPCC AR5 of Working Group 1 covers Earths Glaciers and Ice Caps outside the ice sheets under the heading of Glaciers and shows that, despite much progress recently provided by the community, we are still left with substantial unknowns. We need to acquire more data, both from new fieldwork and release of unpublished data from prior years on mass changes of glaciers and ice caps from all regions of the world. We need to improve the understanding of the processes behind the changes, and we need to improve the application of models of different complexity. We welcome presentations on all aspects of mass changes; current, past and future changes based on field observations, remote sensing and modeling. Studies of physical processes controlling accumulation and ablation including calving and submarine melting, are especially welcome.

Solicited speakers:
Joshua R. Leigh: 'Identifying and mapping very small mountain glaciers on coarse to high-resolution imagery'
Martin Hoelzle: 'Glacier monitoring, capacity building and related cryospheric research in Central Asia'

Public information:
The nominal schedule can be found in the 'Session materials' file.

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Convener: Frank Paul | Co-conveners: Inés Dussaillant, Gwenn Flowers, Jon Ove Hagen, Nicholas Barrand, Matthias Huss, Georg Kaser, Harry ZekollariECSECS
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| Attendance Mon, 04 May, 14:00–18:00 (CEST)

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Session materials Download all presentations (196MB)

Chat time: Monday, 4 May 2020, 14:00–15:45

Chairperson: Frank Paul
D2657 |
EGU2020-5135
Martin Hoelzle, Martina Barandun, Tomas Saks, Erlan Azisov, Abror Gafurov, Alyssa Ghirlanda, Abdulhamid Kayumov, Ruslan Kenzhebaev, Marlene Kronenberg, Horst Machguth, Halim Mamirov, Bolot Moldobekov, Maxim Petrov, Nadine Salzmann, Ryskul Usubaliev, Andrey Yakovlev, and Michael Zemp

Climate change is a major challenge for humanity and the related global implications will influence and threaten future economies and livelihood of coming generations, especially in developing countries. Central Asia is one of the regions mostly vulnerable to climate change considering its hydrological constraints. Tien Shan and Pamir, are among the largest mountain systems of the world, and play a significant role in serving water to the arid and continental region. Future water resources in Central Asia depend strongly on the cryosphere, particularly on snow, glaciers and permafrost. These cryospheric components store enormous amounts of fresh water and under the ongoing climate warming, expected changes will play an important role for future water availability in the region. Recent research clearly points out that a) for current climate conditions, water release by the cryosphere, particularly glaciers, is fundamental to keep runoff sufficient during the dry summer months and b) at the end of this century the water contribution of glaciers will be drastically reduced. Certain catchments are expected to completely dry-out. This setting creates a complex set of future challenges in the domains of water management, energy production, irrigation, agriculture, environment, disaster risk reduction, security and public health and potential political tension and conflicts between the countries cannot be excluded.

Notably, climate change also poses challenges in the field of climate services, as the lack of reliable data and commitment of the governments to fully integrate their observatory systems inhibits the sustainable adaptation and development of the region. At this point, the project CICADA (Cryospheric Climate Services for improved Adaptations) is currently contributing to the improvement of the Cryospheric Climate Services in the Central Asian countries by installing modern monitoring infrastructure, by training local students and researchers and by using the collected in situ measurements in combination with remote sensing and modelling to provide climate scenarios and services for water runoff and natural hazards. This is a prerequisite to allow early planning and adaptation measures within the water resource management and disaster risk reduction sectors.

How to cite: Hoelzle, M., Barandun, M., Saks, T., Azisov, E., Gafurov, A., Ghirlanda, A., Kayumov, A., Kenzhebaev, R., Kronenberg, M., Machguth, H., Mamirov, H., Moldobekov, B., Petrov, M., Salzmann, N., Usubaliev, R., Yakovlev, A., and Zemp, M.: Glacier monitoring, capacity building and related cryospheric research in Central Asia, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5135, https://doi.org/10.5194/egusphere-egu2020-5135, 2020

D2658 |
EGU2020-11382
| Highlight
Daniel Farinotti, Walter W. Immerzeel, Remco J. de Kok, Duncan J. Quincey, and Amaury Dehecq

Due to ongoing climatic change, glacier mass loss and retreat are observed all over the globe. The changes are beyond historic precedence, affect ice masses from the polar ice sheets to the highest mountain glaciers, and cause concerns ranging from rising sea levels to water scarcity. The impacts on water resources are particularly important when glaciers supply water to downstream populations, as is the case in High Mountain Asia (HMA).

Amongst this general picture of glacier wastage, one region stands out because of its anomalous behavior: The Karakoram. Located in the border regions of China, India, and Pakistan, the Karakoram and the nearby Western Kun Lun have been identified as a region in which glaciers were in balance or even slightly gaining mass during recent decades. Geodetic assessments show negligible to slightly positive volume changes, analyses of surface ice flow velocities show steady to increasing ice flow, and glacier inventories reveal a concentration of surge-type glaciers that is unique to HMA.

In this contribution, we review the present-day understanding of what has been known as the “Karakoram Anomaly” since the early 2000s. We show that evidence is accumulating for the Anomaly extending into the Western Kun Lun and Pamirs, and for being due to a combination of factors, including (i) an increase in westerlies-dominated winter snowfalls, (ii) an increase in diurnal temperature ranges possibly related to large-scale deforestation, (iii) a summer cooling linked to the weakening of the monsoon, (iv) an increase in atmospheric moisture likely due to an expansion of  regional irrigation, (v) an increase in summer accumulation resulting from both the summer cooling and the increased moisture, and (vi) reduced ablation due to a moisture-related increase in cloudiness and decrease in incoming shortwave radiation.

Our work assesses the relative level of confidence of the individual mechanisms, and highlights potential pathways that may further improve our understanding.

How to cite: Farinotti, D., Immerzeel, W. W., de Kok, R. J., Quincey, D. J., and Dehecq, A.: Manifestations and mechanisms of the Karakoram glacier Anomaly, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11382, https://doi.org/10.5194/egusphere-egu2020-11382, 2020

D2659 |
EGU2020-21221
Pankaj Kumar, Vladimir A. Ryabchenko, Aaquib Javed, Dmitry V. Sein, and Md. Farooq Azam

Glacier retreat is a key indicator of climate variability and change. Karakoram-Himalaya (KH) glaciers are the source of several perennial rivers protecting water security of a large fraction of the global population. The region is highly vulnerable to climate change impacts, hence the sensitivity of KH glaciers to regional microclimate, especially the impact of individual parameters forcing have been not quantified yet. The present study, using a coupled dynamical glacier-climate model simulation results, analyses the modelled interannual variability of mass-balance for the period 1989-2016. It is validated against available observations to quantify for the first time the sensitivity of the glaciers mass-balance to the individual forcing over KH. The snowfall variability emerges as the key factor, explaining ~60% of the variability of regional glacier mass balance. We provide insight into the recent divergent glacier response over the Karakoram Himalaya. The results underline the need for careful measurements and model representations of snowfall spatiotemporal variability, one of the HK's least-studied meteorological variables, to capture the large-scale, but region-specific, glacier changes at the third pole.

 

 

 

Acknowledgement:

The work was supported by Indian project no. DST/INT/RUS/RSF/P-33/G, and the Russian Science Foundation (Project 19-47-02015).

How to cite: Kumar, P., Ryabchenko, V. A., Javed, A., Sein, D. V., and Azam, Md. F.: Forcings of mass-balance variability in Karakoram-Himalaya, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21221, https://doi.org/10.5194/egusphere-egu2020-21221, 2020

D2660 |
EGU2020-15516
| Highlight
David Loibl, Georgy Ayzel, Fiona Clubb, Inge Grünberg, and Jan Nitzbon

For only two out of more than 95 * 10³ glaciers in High Mountain Asia (HMA) a continuous time series of mass balance measurements covering more than 30 years (World Glacier Monitoring Service’s ‘reference glaciers’) is available to date. Considering that both glaciers are located in the Tian Shan Range, i.e. the northernmost part of HMA, and that glacier changes in HMA is known to be heterogeneous in space and time, it is clear that a substantial knowledge gap exists regarding the actual dynamics at individual glaciers and their forcing. 

Here, we present a novel data set of transient snowline altitude (TSLA) measurements covering all glaciers > 0.5 km² in HMA (n=28,501) for a time frame from the mid 1980s to late 2019 based on more than 10⁵ Landsat satellite images, allowing for investigations of the characteristics of glacier change at unprecedented spatio-temporal resolution and coverage.

Individual glacier’s total maxima of end-of-season TSLAs for the whole period of observation clearly highlight years with many (i.e. 1994, 2009, 2013, 2015) and few (i.e. 1995, 2003, 2012) maxima. Out of the glaciers that show a significant trend throughout the observation period, 90.8% have a positive trend with a median TSLA rise of 7.0 m/year. These figures increase to 95.8% and 13.8 m/year, when only observations of the last two decades are considered.

Based on ERA5 meteorological time series and fundamental physiographic glacier characteristics from the Randolph Glacier Inventory v6, we investigated drivers of the observed TSLA fluctuations. Consistent with expectations, a Random Forest analysis finds temperature to be the dominant meteorological driver of TSLA dynamics throughout all regions of HMA when whole years are considered. Conversely, meteorological forcing regimes are highly heterogeneous for different glaciers in the ablation phase, with wind, air temperature and incoming shortwave radiation being the dominant TSLA drivers for the majority of glaciers in HMA. Considering regional domains, TSLA dynamics are considerably determined by physiographic factors, such as latitude, longitude, hypsographic characteristics, slope and aspect of individual glaciers. A hierarchical clustering analysis shows distinct groups of similar forcing setups exist; Their spatial distribution, however, rather follows specific positions in the topoclimatic system than forming distinct regional clusters or aligning to large-scale gradients.

In summary, our findings indicate that spatial and temporal patterns of glacier change in HMA are considerably more complex than currently known. Multidecadal high-resolution TSLA datasets like the one presented here may inform future research to disentangle the complex topoclimatic process-response systems that control the adaptation of individual glaciers to climate change.

How to cite: Loibl, D., Ayzel, G., Clubb, F., Grünberg, I., and Nitzbon, J.: Dynamics and drivers of High Mountain Asia’s glacier change from the mid 1980s to late 2019, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15516, https://doi.org/10.5194/egusphere-egu2020-15516, 2020

D2661 |
EGU2020-17796
David Farías, Philipp Malz, Thorsten Seehaus, Christian Sommer, Lukas Sochor, and Matthias Braun

Patagonian and Tierra del Fuego Glaciers are among the highest contributors to sea level rise in the Southern Hemisphere. Although this is an area gaining more attention through recent studies, continuous remotely sensed monitoring is only nascent, but crucial for a better understanding of the glacier changes in this region. Here, we present an update of the glacier elevation and mass changes of Patagonia and Tierra del Fuego glaciers, applying differential synthetic aperture radar (SAR) interferometry using data from the Shuttle Radar Topography Mission (SRTM) and the German TerraSAR-X-Add-on for Digital Elevation Measurements mission (TanDEM-X). Our study covers the period between 2000 and 2019. Here, we particularly estimated the glacier mass loss regionalized for the Northern and Southern Patagonia Icefield (NPI and SPI) and Tierra del Fuego, which includes the Icefields of Cordillera Darwin and Gran Campo Nevado.

Our preliminary results indicate mass loss rates of 4.75 ± 0.35 Gt a-1 for NPI for the period of 2000-2019. Results for both other regions will be also presented. Alongside an accuracy assessment based on GNSS field campaign data and satellite laser altimetry.  

How to cite: Farías, D., Malz, P., Seehaus, T., Sommer, C., Sochor, L., and Braun, M.: Ice loss in Patagonia and Tierra del Fuego glaciers during the first two decades of the 21st century, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17796, https://doi.org/10.5194/egusphere-egu2020-17796, 2020

D2662 |
EGU2020-13782
Riccardo Barella, Mattia Callegari, Carlo Marin, Claudia Notarnicola, Marc Zebisch, Rudolf Sailer, Christoph Klug, Shtephan Galos, Roberto Dinale, and Stefano Benetton

Glaciers represent an important part of the hydrologic cycle in the Alps and they are very sensitive to climate change. Satellite remote sensing is an efficient tool for glacier monitoring because it provides a synoptic view over large areas. In literature, well-established methods for glacier delineation based on the Red and Short Wave Infrared (SWIR) ratio have been presented. These methods depend on a manual selection for each glacier of the “best scene”, i.e. absence of cloud coverage and minimum snow cover. A further manual refinement step is needed to handle possible errors, mainly due to cloud cover or shadows, and to include debris covered ice.

A manual approach for glacier outline extraction, especially if applied over large areas and beside the respective extraordinary amount of work, may be inadequate for at least two reasons:

1) The increased amount of available satellite data provided by the recently launched Sentinel-2 mission, which ensure at least one acquisition every 5 days on a given area;

2) The need for a more frequent update of the glacier outlines i.e. few years, due to the faster changes affecting glaciers during the last years.

In this work, we present an automatic method for glacier mapping, including bare ice and debris covered ice through the synergetic use of Sentinel-1 and Sentinel-2. The information of the Sentinel-2 time series is first classified with a Support Vector Machine (SVM) to detect cloud and snow. The snow and cloud masks are then used to select the non-cloudy pixels with the lowest snow coverage in the surrounding area. This is done by applying a moving window on the entire multi-temporal classified stack. The selected pixels for each band compose a multi-temporal cloud free mosaic, which represents the glaciers with the minimum snow cover for the current ablation season i.e., the “best scene”. If we compose the mosaic with classified pixels instead of the reflectance, we obtain the glacier – non glacier map that we use for outlines extraction. On the other hand, the Sentinel-1 coherence is used to detect the debris-covered ice over the areas classified as non-glacier from Sentinel-2. In detail, the Sentinel-1 time series is exploited to generate a multi-temporal coherence mosaic, which is representative of the loss of coherence due to the movement of the debris only. By properly thresholding this mosaic and considering the topographic information, the outlines of debris covered glaciers can be extracted.

The results obtained with the proposed method are compared with the recent official glacier inventory of South Tyrol (Italy) and Tyrol (Austria), which was derived from the manual interpretation of aerial orthophotos and lidar data by glacier experts.

How to cite: Barella, R., Callegari, M., Marin, C., Notarnicola, C., Zebisch, M., Sailer, R., Klug, C., Galos, S., Dinale, R., and Benetton, S.: Automatic glacier outlines extraction from Sentinel-1 and Sentinel-2 time series, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13782, https://doi.org/10.5194/egusphere-egu2020-13782, 2020

D2663 |
EGU2020-21056
Tatiana Khromova, Gennady Nosenko, Andrey Glazovsky, Stanislav Nikitin, and Anton Muraviev

We present new Glacier Inventory of the Russian glaciers based on Sentinel images (2017/2018).

The modern reduction in the size of glaciers is accompanied by the activation of natural processes leading to catastrophic consequences, changes in landscapes and prevailing nature management practices. To reduce risks and adapt to the consequences of ongoing changes, relevant data on the state of glacial systems are needed. In Russia, extensive glaciation is present in the Arctic zone, and in its continental part there are 18 mountain-glacial systems. According to the Glacier Inventory of the USSR in the mid-twentieth century in Russia there were 7167 glaciers with a total area of ​​60103, 99 km2. Of these, 685 glaciers with an area of ​​56,127.2 km2 accounted for the Arctic archipelagos. Despite the ever-increasing amount of information from space, and experimental studies in a number of glacial regions, a complete and reliable picture of the state of glaciation in Russia at the beginning of the 21st century has not been available to date.
The project aims to develop and create a unified information basis for the study of glacial regions of Russia using geoinformation technologies. The initial data were collected and systematized to assess the current state of Russia's glaciers: data from previous inventories, maps, historical and modern aerial and space images, digital elevation models. A classification of possible catastrophic phenomena of glacial genesis was developed: dynamically unstable glaciers, glacier lakes, icebergs, etc. The structure of the database for the study of Russian glaciers is developed, compatible with world and national data archives. Implementation of the project allowed to gain new knowledge about the state of Russian glaciers.

The presentation includes the results obtained in the framework of the following research projects: № 0148-2019-0004 of the Research Plan of the Institute of Geography of the Russian Academy of Sciences, № 05/2019/RGS-RFBR supported by the Russian Geographical Society, № 18-05-60067  supported by RFBR.

How to cite: Khromova, T., Nosenko, G., Glazovsky, A., Nikitin, S., and Muraviev, A.: New Glacier Inventory of the Russian glaciers based on Sentinel images (2017/2018)., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21056, https://doi.org/10.5194/egusphere-egu2020-21056, 2020

D2664 |
EGU2020-3901
Joshua Leigh, Chris Stokes, Rachel Carr, Ian Evans, Liss Andreassen, and David Evans

Small mountain glaciers are an important part of the cryosphere and tend to respond rapidly to climate warming. Historically, mapping very small glaciers (generally considered to be <0.5 km2) using satellite imagery has often been subjective due to the difficulty in differentiating them from perennial snowpatches. For this reason, most scientists implement minimum size-thresholds (typically 0.01–0.05 km2). However, when mapping on high-resolution imagery (<1 m) with minimal seasonal snow cover, glaciers <0.05 km2 and even <0.01 km2 are readily identifiable and using a minimum threshold may be inappropriate. For these cases, we have developed a set of criteria to enable the identification of very small glaciers and classify them as certain, probable, or possible. Our identification criteria are based on detailed ice surface structures (e.g. evidence of flow banding and crevasses) and diagnostic glacial landforms (e.g. moraines). Implementation of this scoring system should facilitate a more consistent and objective approach to identifying and mapping very small glaciers on high-resolution imagery, helping to produce more comprehensive and accurate glacier inventories.

How to cite: Leigh, J., Stokes, C., Carr, R., Evans, I., Andreassen, L., and Evans, D.: Identifying and mapping very small mountain glaciers on coarse to high-resolution imagery, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3901, https://doi.org/10.5194/egusphere-egu2020-3901, 2020

D2665 |
EGU2020-2638
| Highlight
Michael Zemp, Matthias Huss, Nicolas Eckert, Emmanuel Thibert, Frank Paul, Samuel U. Nussbaumer, and Isabelle Gärtner-Roer

Comprehensive assessments of global glacier mass changes based on a variety of observations and prevailing methodologies have been published at multi-annual intervals, typically towards IPCC reports. For the years in between, the glaciological method provides annual observations of specific mass changes but is suspected to not be representative at the regional to global scales due to uneven glacier distribution with respect to the full sample. Here, we present a framework to infer ad hoc (i.e., timely but preliminary) estimates of global-scale glacier contributions to sea-level rise from annual updates of glaciological observations. For this purpose, we combine the annual anomaly provided by the glaciological sample (relative to a decadal mean) with the (mean) absolute mass-change rate of a global reference dataset over a common calibration period (from 2006/07 to 2015/16). As a result, we provide preliminary estimates of regional and global glacier mass changes and related uncertainties for the latest hydrological years; i.e. about –300 ± 250 Gt per year in 2016/17 and –500 ± 200 Gt per year in 2017/18. These ad hoc estimates indicate that glacier contributions to sea-level rise exceeded 1 mm SLE per year which corresponds to more than a quarter of the currently observed rise. We also discuss the regional biases of the glaciological sample and conclude with a brief outlook on possible applications and remaining limitations of the glaciological observation network of the World Glacier Monitoring Service.

How to cite: Zemp, M., Huss, M., Eckert, N., Thibert, E., Paul, F., Nussbaumer, S. U., and Gärtner-Roer, I.: Ad hoc estimation of glacier contributions to sea-level rise from latest glaciological observations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2638, https://doi.org/10.5194/egusphere-egu2020-2638, 2020

D2666 |
EGU2020-16031
| Highlight
Bert Wouters, Alex Gardner, Geir Moholdt, and Ingo Sasgen

Glaciers outside of the ice sheets are important contributors to sea level rise. Although their overall mass balances can be estimated by upscaling local field measurement, direct observations with global coverage are only feasible with satellite remote sensing.  Satellite gravimetry of the Gravity Recovery and Climate Experiment (GRACE) showed that between 2002 and 2016, glaciers lost mass at a rate of 199 ± 32 Gt yr−1, equivalent to a cumulative sea level contribution of 8 mm. After about one year of interruption following the end of the GRACE science operations in June 2017, GRACE Follow-On (GRACE-FO) now allows us to extend the time series of its predecessor starting June 2018.

In this work, we provide updated estimates of the global glacier annual mass balance for 2002 and 2019 based on GRACE/GRACE-FO, and present regional changes with a focus on recent years. Furthermore, we discuss the different uncertainties entering our mass balances and compare our estimates to those based on upscaling in-situ measurements.

How to cite: Wouters, B., Gardner, A., Moholdt, G., and Sasgen, I.: Global Glacier Mass Loss estimated from GRACE and GRACE-FO Satellite Observations (2002-2019), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16031, https://doi.org/10.5194/egusphere-egu2020-16031, 2020

D2667 |
EGU2020-11020
Carleen Reijmer, Abas Khan, Eric Rignot, Michiel van de Broeke, and Brice Noël

In August 2016, two automatic weather stations (AWS) were placed on Zachary glacier, North East Greenland. They were installed in support of a project investigating the surface mass balance, ice velocity and calving conditions of Zachary glacier. The stations are full energy balance stations, i.e. they measure all parameters (air temperature, wind speed, relative humidity, air pressure, and short and long wave incoming and outgoing radiation) necessary to derive the full surface energy balance. In addition, the stations are equipped with a sonic height ranger in combination with a draw wire to measure snow accumulation and ice melt, respectively, and a GPS to monitor glacier velocity. These stations provide insight in the local climate of north east Greenland, a region for which only limited in situ data is available.

The AWS were located initially at ~145 m a.s.l., about 13 km from the glacier front (AWS23), and at  ~535 m a.s.l., about 35 km from the glacier front (AWS22). Both are moving reasonably fast (0.7 – 1.7 km/yr) towards the front, which has an impact on observed variables mainly since station elevation decreases, although changing (surrounding) topography impacts wind and radiation observations as well. Results show that both sites exhibit a strong katabatic signature, with directional constancies around 0.9, and wind speeds in winter being twice as strong as in summer. Temperature difference between the sites reflect the height difference, and is smaller in summer due to the melting surface impacting the near surface temperature. The lapse rate increases from ~0.5 °C/100 m in summer to ~0.7°C/100 m in the other seasons. The lower station, AWS23, is located in the ablation zone and has experienced on average 2.1 m ice melt over the past 3 years. At the higher station the mass budget appears to be in balance over this period.

The 3.5 years of available station data is compared with regional climate model RACMO2.3p2 output (5.5 km resolution), where monthly averaged data from the grid point nearest to the average station location is used. Initial differences in surface pressure reflect a difference in model grid height and station elevation (stations being located at lower elevation), while an increase in the absolute difference reflects the fast movement of the glacier transporting the AWS to lower elevations (30 and 70 m lowering for AWS22 and 23 respectively). The model overestimates temperature at AWS22 (1.3 °C), and wind speeds are too high at both sites.

How to cite: Reijmer, C., Khan, A., Rignot, E., van de Broeke, M., and Noël, B.: Local climate of Zachary glacier, North East Greenland, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11020, https://doi.org/10.5194/egusphere-egu2020-11020, 2020

D2668 |
EGU2020-18096
Stanislav Kutuzov, Andrey Smirnov, Gennady Nosenko, Ivan Lavrentiev, Aleksei Poliukhov, Nelly Elagina, and Stanislav Nikitin

The ice-covered Europe's largest volcanic massif Elbrus (5,642 m) is a unique object for studying the reaction of mountain glaciers to climate changes. Elbrus glacial system contains more than 10% of the total ice volume in the Greater Caucasus. Elbrus glaciers influence on the recreation development. The rivers runoff from the Elbrus glaciers irrigates agricultural lands on steppe plains of the North Caucasus.

The rate of glacier reduction in the late XX - early XXI centuries has increased significantly and in 1997-2017 Elbrus have lost 23% of its volume. Despite a number of glacier studies the mechanisms and quantitative characteristics surface mass exchange on Elbrus are still uncertain. Mass balance calculations were based on limited data. In particular, amount and distribution of snow accumulation, mass balance sensitivity to meteorological parameters under dramatic climate changes and other parameters remained unknown.

Here we present the results of the detailed analysis of Garabashi glacier mass changes in 1982-2019 using glaciological and geodetic methods. Based on the new data of snow and ablation distribution the mass balance measurement system of Garabashi glacier was improved in 2018-2019. The mass balance over the studied period was also modelled using both temperature-index and distributed energy mass balance models calibrated by in situ measurements and albedo estimates from the remote sensing.

The mass balance of the Garabashi glacier was close to zero or slightly positive in 1982-1997 and the cumulative mass balance was 1 m w.e. in this period. In 1997-2017 Garabashi glacier lost 12.58 m w.e. and 12.92 ± 0.95 m w.e. (−0.63 and −0.65 ± 0.05 m w.e. a−1) estimated by glaciological and geodetic method, respectively. Additional -1.7 m w.e. were lost in 2018-2019. This resulted in an area reduction by 14% and a loss of 27% of glacier volume. The observed glacier recession is driven by the pronounced increase in summer temperatures, especially since 1995, which is accompanied by nearly consistent precipitation rates The increase in incoming shortwave radiation, also played a significant role in the accelerated mass loss of glaciers in Caucasus. This study was supported by the RFBR grant 18-05-00838 a

How to cite: Kutuzov, S., Smirnov, A., Nosenko, G., Lavrentiev, I., Poliukhov, A., Elagina, N., and Nikitin, S.: Garabashi glacier (Caucasus) mass changes estimated from glaciological and geodetic mass balance measurements, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18096, https://doi.org/10.5194/egusphere-egu2020-18096, 2020

D2669 |
EGU2020-9125
Qinghua Ye, Wei Nie, Yimin Chen, Gang Li, lide Tian, Liping Zhu, and Jeff S Kargal

Glaciers in the central Himalayas are important water resources for the downstream habitants, and accelerating melting of the high mountain glaciers speed up with continuous warming. We summerized the geodetic glacier surface elevation changes (Dh) by 6 data sets at different time periods during 1974-2016 in RongbukCatchment(RC) on the northern slope of Mt. Qomolangma (Mt. Everest) in the Central Himalayas. The result showed that glacier Dh varied with altitude and time, from -0.29 ± 0.03m a-1 in 1974-2000, to -0.47 ±0.24 m a-1 in 1974-2006,and -0.48 ±0.16 m a-1 in 1974-2012. Dh increased to -0.60 ± 0.20 m a-1 in 2000-2012, then decreased to-0.46 ± 0.24 m a-1 in 2000-2014, and by -0.49 ± 0.08 m a-1 in 2000-2016, showing a diverse rate being up - down- a little up. However, it generally presented a similar glacier thinning rate by -0.46~-0.49 m a-1 in the last four decades since 1970s in RC according to Dh1974-2006, Dh1974-2012, Dh2000-2014, and Dh2000-2016. Local meteorological observations revealed that, to a first order, the glacier thinning rate was kept the same pace with the number of annual melting days (MD). In spite of the obviously arising summer air temperature (TS) in 2000-2014, a slowdown glacier melting rate by -391 mm w.e.a-1 occurred in 2000-2014 because of less melting days with more precipitation and less annual mean temperature(Tm). It shows that MD is another important indicator and controlling factor to evaluate or to estimate glacier melting trend, especially in hydrological or climate modeling.

How to cite: Ye, Q., Nie, W., Chen, Y., Li, G., Tian, L., Zhu, L., and Kargal, J. S.: Glacier surface elevation changes in Rongbuk Catchment of the Central Himalayas in the last four decades, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9125, https://doi.org/10.5194/egusphere-egu2020-9125, 2020

D2670 |
EGU2020-951
Mohd Soheb, Alagappan Ramanathan, and Sonam Lotus

An analysis of mass balance (MB), runoff and area of a group of small glaciers (< 1 km2) in Stok region, Ladakh, India, was conducted to investigate their behaviour in past few decades. These glaciers are essential to the downstream village of ~300 households as they are entirely dependent on the ice and snow meltwater for domestic and agricultural use. The study presents an in-situ (2014-2019) and historical modelled MB (1978-2019) of Stok glacier, which is first of its kind in Ladakh region. The observed MB was found to be negative since 2014 with an average MB of -0.4 m w. e. a-1. However, modelled MB showed a balanced condition during 1980s, followed by a severe retreat in the first decade of 21st century. MB sensitivity analysis suggests that the winter precipitation and summer temperature are almost equally significant in driving mass balance of the glacier and water resources. Around 27% increase in precipitation is required to compensate the melt due to 1°C rise in temperature. Net changes of glacier extent were determined from a detailed manual comparison of remotely sensed imagery acquired between 1969 to 2019 by the high-resolution declassified Corona mission, Landsat ETM+/OLI and PlanetScope satellites. All the glaciers in this region retreated with different rates during different periods. Overall, the reduction in glacier extent was found to be around -0.73 km2 (-0.016 km2 a-1) equivalent to ~15% of the total glacier extent, in the past five decades. Runoff from the catchment was also modelled with the help of available temperature, precipitation and remote sensing data. The runoff model was calibrated and validated using daily in-situ discharge data of two summers (2018 and 2019). It was found that the runoff was highest during July and August months due to both increased snow and ice melt. Winter precipitation in this region is essential not only for glacier health but for early spring sowing season when the demand for the water is highest, and snowmelt water is the only source of early streamflow. Thus, this study assumes greater significance in light of an perceptible shift in precipitation from winter to summer in past two decades, which needs further investigation.

How to cite: Soheb, M., Ramanathan, A., and Lotus, S.: Long-term mass balance, runoff and area change in Stok group of glaciers, Ladakh, India, between 1969 to 2019., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-951, https://doi.org/10.5194/egusphere-egu2020-951, 2019

D2671 |
EGU2020-3466
Isabelle Gärtner-Roer, Samuel U. Nussbaumer, Fabia Hüsler, and Michael Zemp

Glaciers impact the lives of millions of people whose drinking water supply, energy production, and irrigation-dependent agriculture is disrupted as the glaciers melt. Knowledge on glacier distribution and quantification of glacier changes is crucial to assessing the impact of glacier shrinkage on the society. Therefore, glacier monitoring is vital to the development of sustainable adaptation strategies in regions with glaciated mountains.

Detailed information on national glacier monitoring, including data on glacier distribution as well on as glacier changes, is compiled in a standardized procedure to summarize and also compare the situation in each of the glacierized countries. The resulting country profiles are assessed in relation to the existing monitoring strategy of the Global Terrestrial Network for Glaciers (GTN-G). Gaps between the current implementation of glacier monitoring and implementation targets are analyzed in a solid gap analysis, which allows countries to be categorized as having poorly developed monitoring, needing improvement, or having well-developed monitoring. By this, it is intended to raise awareness of the challenges for the individual national monitoring systems and to illuminate what future needs might be to improve the situation.

The study is meant to provide a baseline for scientists and decision-makers in international organizations, national governments, and local communities, as they take responsibilities to improve glacier monitoring systems and care about their relevance in decision-making processes.

How to cite: Gärtner-Roer, I., Nussbaumer, S. U., Hüsler, F., and Zemp, M.: National glacier monitoring – strengths and weaknesses, responsibilities and priorities, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3466, https://doi.org/10.5194/egusphere-egu2020-3466, 2020

D2672 |
EGU2020-18972
Andrey Smirnov, Stanislav Kutuzov, Aleksandr Erofeev, Sergey Kopysov, Ivan Lavrentiev, Zamir Abbasov, and Kirill Nikitin

The rate of glaciers decline in the late 20th-early 21st centuries increased substantially. These circumstances are of particular relevance in mountainous areas, where glaciers are one of the most important landscape-forming factors, regulate river flow and serve as a potential source of hazardous processes and phenomena that threaten economic and recreational activities. The Aktru Glaciers (Maliy Aktru since 1962, Leviy Aktru and Vodopadniy since 1977) are the ‘reference’ glaciers of the World Glacier Monitoring Service (WGMS).

The Aktru glacier monitoring programs were suspended in 2012. There were only two glaciers with a continuous series of measurements in Russia. Both of these glaciers are located in the Caucasus. The vast area of Northern Eurasia at the current time is not covered with direct measurement data on glaciers, which does not allow to validate the results of global and regional projections of climate and environmental change and causes serious concern to the scientific community.

Here we present the first results of mass balance measurements on Leviy Aktru glacier re-established in 2019. The detailed accumulation measurements supplemented with new ablation stakes network and AWS enabled calculation of the mass balance of -425 mm w.e. in 2018/19. Ice thickness and bedrock topography was estimated using the GPR measurements. Additionally, the glacier volume changes from 2000 to 2019 were assessed for the region using SRTM-X and Pleiades DEM. The data obtained can be used to validate regional hydrological and mass balance models for Altai mountains.

The Pléiades stereo-pair used in this study was provided by the Pléiades Glacier Observatory initiative of the French Space Agency (CNES).

How to cite: Smirnov, A., Kutuzov, S., Erofeev, A., Kopysov, S., Lavrentiev, I., Abbasov, Z., and Nikitin, K.: Re-establishing mass balance measurements on Aktru glaciers (Altai)., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18972, https://doi.org/10.5194/egusphere-egu2020-18972, 2020

D2673 |
EGU2020-9814
Niccolò Dematteis, Daniele Giordan, and Fabrizio Troilo

 

Glaciological phenomena can have a strong impact on human activities in terms of hazards and freshwater supply. Therefore, a scientific observation is fundamental to investigate their current state and recent evolution. To this aim, experimenting innovative scientific survey methodologies and equipment is of primary importance. Strong efforts in this field have been spent in the glacial complex of the Grandes Jorasses massif (Mont Blanc area), where several ice break-offs glacial outburst triggered from the Planpincieux Glacier snout and the Whymper Serac and threatened the underling Planpincieux valley in the past. From 2009, the glacial complex has become an open filed laboratory where a wide set of close-range remote sensing survey systems have been developed and applied to investigate the glacial state and dynamics.

Two continuous monoscopic time-lapse cameras observe the Planpincieux Glacier since 2013. Digital image correlation is applied to the photographs to measure the surface kinematics at different level of detail. During the monitoring, image analysis techniques allowed at classifying the instability processes of the terminus and at estimating the volume of the break-off events. Such investigation revealed the presence of possible break-off precursors and a monotonic relationship between glacier velocity and break-off volume, which might help for risk evaluation.

A robotised total station (RTS) is active since 2009 to monitor the Whymper Serac velocity (Grandes Jorasses Glacier). The operative distance between the total station and targets is approximately 5000 m. A network of several prisms is installed onto the serac, but the extreme conditions related to the high-mountain environment force to replace periodically the stakes that are lost. Besides the RTS, a monoscopic camera acquires hourly images of the serac for surface velocity measurements.

In addition to the permanent monitoring systems, surveys with four different terrestrial interferometric radars have been conducted in the Planpincieux Glacier between 2013 and 2019. Helicopter-borne LiDAR and terrestrial laser scanner provided the DEM of the Planpincieux Glacier in 2014 and 2015 respectively. A sequence of six DEMs has been also produced by aerial and UAV structure from motion in the time span 2017-2019. Finally, a helicopter ground penetrating radar campaign was conducted in 2013 to evaluate the thickness of the Planpincieux Glacier and Whymper Serac.

For what concerns the mountain glaciers, the survey activity conducted in the Grandes Jorasses massif since 2009 is probably one the most intensive and variegated in European Alps. This makes such an environment an open-air laboratory for experimenting close-range remote sensing monitoring systems that it is ready for new research activities and monitoring solutions development.

 

 

How to cite: Dematteis, N., Giordan, D., and Troilo, F.: Glaciers of Grandes Jorasses: an open-air laboratory for glacier monitoring systems development, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9814, https://doi.org/10.5194/egusphere-egu2020-9814, 2020

D2674 |
EGU2020-18934
Andreas Linsbauer, Elias Hodel, Matthias Huss, Andreas Bauder, Mauro Fischer, Yvo Weidmann, and Hans Bärtschi

A glacier inventory describes the extent of all glaciers at a given point in time and in periods of rapid glacier change a frequent update is needed. The Swiss Glacier Inventory 2010 (SGI2010) is the last official inventory for Switzerland and was derived by manual digitization from high-resolution (25 cm) aerial orthophotographs from swisstopo (Federal Office of Topography). To regularly produce a revised inventory, based on the high-quality aerial images from swisstopo acquired at a three-year interval, the workload cannot be covered by GLAMOS (Glacier Monitoring Switzerland, www.glamos.ch) on its own. As part of the development of the new topographic landscape model of Switzerland (swissTLM3D), swisstopo introduced – based on requirements defined by GLAMOS – the object class “glaciers”. This secures that Swiss glaciers are recurrently mapped based on high-resolution data on a long term. Swiss Glacier Inventories can therefore be derived by GLAMOS from the TLM object class “glaciers”.

The SGI2020 is the first glacier inventory produced by GLAMOS based on the new workflow and stands out with an unprecedented level of detail regarding glacier mapping. As the glacier-excerpt from the swisstopo TLM is a landcover dataset, produced according to guidelines for topographical purpose, it does not fit all glaciological requirements. Here, we present the necessary steps and adjustments to derive a new glacier inventory for the period 2013-2018 that fits all glaciological criteria. Furthermore, we compare the resulting dataset with former SGI’s and pin down the major changes and differences emerging from different methodologies used. We particularly emphasize on problematic definitions of glacier boundaries related to snow coverage and/or supraglacial debris and provide updated results for glacier area changes in the Swiss Alps over the last decades.

How to cite: Linsbauer, A., Hodel, E., Huss, M., Bauder, A., Fischer, M., Weidmann, Y., and Bärtschi, H.: The new Swiss Glacier Inventory SGI2020: From a topographic to a glaciological dataset, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18934, https://doi.org/10.5194/egusphere-egu2020-18934, 2020

D2675 |
EGU2020-9888
Fabien Maussion, Regine Hock, Frank Paul, Philipp Rastner, Bruce Raup, and Michael Zemp

The Randolph Glacier Inventory (RGI) is a globally complete collection of digital glacier outlines, excluding the two polar ice sheets. It has become a pillar of glaciological research at global and regional scales, among others for estimates of recent and future glacier changes, glacier mass balance, and glacier contribution to sea-level rise. After its creation in 2012, the dataset’s further development has been coordinated by an IACS Working Group (WG) until 2019. This new WG (2020 - 2023) expands the scope of the previous one with new and updated objectives.

The latest RGI version (V6) was released in July 2017, and several new glacier outline datasets have been generated by the community since then. In the past, the RGI was updated by an ad-hoc manual process, which was effective but labor-intensive. One of the main objectives of the WG is to automate this process as much as possible by incorporating RGI generation tools into the Global Land Ice Measurements from Space (GLIMS) glacier database. Furthermore, the RGI (as of version 6) needs further improvements  to remain useful to the wider scientific community. Examples include data quality (wrong/outdated outlines, ice divides) but also the quality and availability of glacier attributes (hypsometry, glacier type, ...). Additionally, there is a demand for consistent historic glacier outlines (e.g. from the mid-1980s or earlier) to facilitate validation of glacier evolution models or transient mass balance calculations. With this WG, we strive to continuously improve and update the RGI, as well as to lay out a long-term plan for sustainable continuation of the RGI beyond the end of this WG.

In this presentation, we will discuss the current status and future of the RGI, and will engage with the community to encourage participation and feedback.

How to cite: Maussion, F., Hock, R., Paul, F., Rastner, P., Raup, B., and Zemp, M.: A new working group on the Randolph Glacier Inventory (RGI) and its role in future glacier monitoring, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9888, https://doi.org/10.5194/egusphere-egu2020-9888, 2020

D2676 |
EGU2020-12515
Hester Jiskoot, Easton DeJong, Wesley Van Wychen, and Jade Cooley

One of the outstanding glaciological research questions is how glaciers respond dynamically to climate change and how this varies regionally. Ice-velocity changes occur on an interannual scale in response to mass-balance forcing changing the glacier geometry and therefore the driving stress. For a glacier tending towards steady-state the mass flux through a cross-section equals the mass balance upstream of the cross-section. Mass loss will, therefore, usually lead to a slowdown of glaciers. However, a changing climate can also affect the occurrence of sliding and change a glacier’s thermal regime and its marginal processes (ice-ocean, ice-lake and ice-bed interactions). The response of glacier flow to climate change is, therefore, not straightforward, and mass loss combined with increased meltwater production or a transition to a temperate regime may lead to an increase in flow speed. Ultimately, depending on their individual response time, glaciers respond in a delayed dynamical way to changes in mass balance.

Various recent publications have addressed the above research question at regional scales by analysing decadal changes in flow speed in relation to glacier mass loss. Only few local works, however, have addressed the question in the context of measured differences between actual and balance velocities. The recent generation of diverse global glacier datasets, such as the Randolph Glacier Inventory (RGI), GoLIVE and ITS_LIVE ice speed, ice thickness, and globally-distributed datasets such as WGMS mass balance data and companion ground measurements, offer opportunities to address outstanding research questions in interregional to global perspectives. We will compare, for the first time, for glaciers in various RGI subregions the difference between the measured glacier velocity, derived from available GoLIVE and ITS-LIVE datasets and additional speckle tracking from SAR scenes, and the balance velocity, derived using mass balance profiles, hypsometry, and ice thickness datasets. We use the standard approach of deriving balance flux along a flowline, and use a scenario-based approach to deal with measurement and model uncertainties. In this poster we present the results for approximately 20 glaciers in Canada and Iceland in detail. Ultimately, we aim to use more than 200 glaciers with WGMS and independent long-term mass balance records, distributed over the 19 RGI first-order regions and as many as the 89 second-order regions as possible.

How to cite: Jiskoot, H., DeJong, E., Van Wychen, W., and Cooley, J.: The need for global glacier speed to combine measured velocity with balance velocity, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12515, https://doi.org/10.5194/egusphere-egu2020-12515, 2020

D2677 |
EGU2020-10734
Simona Gennaro, Maria Cristina Salvatore, Linda Alderighi, Riccardo Cerrato, and Carlo Baroni

Alpine glaciers are sensitive key markers of climate variations, as their geometry and shape are the results of adjustments in response to changes of their mass balance. Since the Little Ice Age the European Alps, as well as other mountain ranges, experienced a phase of generalized retreat, accentuated during the last decades. The availability of quantitative data on glaciers variations from major mountain regions represent relevant tools for better understanding the glacier behaviour in response to ongoing climatic changes. Here we present new data on Holocenic variations of glaciers hosted in the Gran Paradiso Massif, the first Italian National Park (Western Italian Alps).

We built the multi-temporal digital inventory of the Gran Paradiso Massif glaciers covering a time period of over 150 years, considering distinct time steps spanning from the Little Ice Age (LIA) to 2015. The multi-temporal dataset was built including glaciers outlines (derived from high resolution orthophotos and historical maps) and the data related to frontal variations (coming from annual glaciological surveys conducted by the Italian Glaciological Committee). Database was managed in GIS environment and populated following the guidelines suggested by the WGMS. Multi-temporal analysis supplied new quantitative data on the strong glacial decline occurred since the LIA and dramatically accelerated since the 90s.

During the LIA the Gran Paradiso Massif hosted more than 120 glaciers extended for about 112 km2 reduced to 73 units in 2015 covering only about 32 km2.

Our data underline a loss of about 50 ± 4 m w.e. and ELA variations of about 166/130 ± 5/4 m (considering AAR/AABR methods, respectively) from the maximum LIA position and 2006. The strong contraction and fragmentation of the studied glaciers is underlined by area loss of over 71% (with a reduction rate of -0.36% y-1) from the LIA to 2015, as well as by the increase in the number of glacial bodies smaller than 0.1 km2, and by the increase in the number of extinct glaciers (33 in 2015 respect to 1957). Furthermore, during the last decades, new data obtained show a dramatic acceleration in the contraction rates of the glacial bodies, which can lead to impressive landscape changes and to a relevant increase of geomorphological hazard.

The multitemporal data show a very detailed evolution of Gran Paradiso glaciers also considering ice- mass loss and can contribute to modelling glaciers response to climate changes in a sensitive area of the Italian Alps, considering its location at the border of a “dry zone”. Improving the knowledge on the glacial resource could contribute in better understanding the impact of warming climate on mountain hydrology, as well as to increase the awareness of the population and authorities to be resilient in a near future with strong reduction of meltwater runoff.

How to cite: Gennaro, S., Salvatore, M. C., Alderighi, L., Cerrato, R., and Baroni, C.: Glacial reduction in the Gran Paradiso Massif (Western Italian Alps): multitemporal dynamic inventory since the Little Ice Age , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10734, https://doi.org/10.5194/egusphere-egu2020-10734, 2020

D2678 |
EGU2020-18666
Sergey Sokratov, Yuri Seliverstov, Alla Turchaniniva, Evgenii Kharkovets, and Heitor Evangelista da Silva

We investigated the long-term dynamics of four glaciers that are part of the nival-glacial system of Mount Elbrus and located on its southern slope: Terskol, Garabashi, Malyi Azau, Bol’shoi Azau. The time period of the study covers 1887–2017. Glaciological measurements were carried out using DEM, compiled from early-year maps and from the results of stereo surveys in 2017, made by UAVs and high-resolution digital camera. New results present the change in the area of these glaciers, the elevation of their lowest points and the height of the surface. All these characteristicsindicate decrease of glaciation at the southern slope of Elbrus and intensification of this process in the last decade. Some differences in dynamics of changes of different glaciers can be explained by differences in their morphological types, morphometric indicators, the state of the beds, which we do not have much information about. Additionally, cores of two near glaciers lakes sediments were extracted and analyzed, offering high resolution record of sedimentation. The age of the bottom lake sediments near Malyi Azau glacier corresponds to documented beginning of the lake formation due to glacier ice retreat in 1950th. The other lake to the side of the Garabashi glacier was formed much earlier and the upper 15 cm of the lake sediments core is formed between 1893 and 2016.

The obtained results are compared with the results of other investigations. We believe that the new data of glaciers dynamics is more accurate and more promising in understanding the specific of accumulation and melt in dependence on elevation, slopes aspect s and angle.

How to cite: Sokratov, S., Seliverstov, Y., Turchaniniva, A., Kharkovets, E., and Evangelista da Silva, H.: Change in Mt. Elbrus nival-glacial system in the last century, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18666, https://doi.org/10.5194/egusphere-egu2020-18666, 2020

Chat time: Monday, 4 May 2020, 16:15–18:00

Chairperson: Harry Zekollari
D2679 |
EGU2020-9339
Catrin Stadelmann, Johannes Fürst, Thorsten Seehaus, Thomas Mölg, and Matthias Braun

The glaciers on Kilimanjaro are unique indicators for climatic changes in the tropical mid-troposphere of Africa. Glaciers in the tropics have shown a severe retreat since the Last Glacial Maximum and the glaciers on Mt. Kilimanjaro are no exception, with an 85% reduction in glacier area from 1912 to 2013. This history of severe glacier area loss raises concerns about an imminent future disappearance. Yet, the remaining ice volume is not well known.

By combining state-of-the-art techniques from satellite remote sensing and glacier mass balance modelling with data assimilation, we inferred the  glacier ice thickness of two selected glaciers on Mt. Kilimanjaro. We reconstruct thickness maps for 2000 and 2011 for the Northern Icefield and Kersten Glacier and find mean thickness values of 26.6 and 9.3 m for 2011, respectively. Model validation was difficult for Kersten Glacier, as no ice thickness  measurements were available. Thus, the first attempt to use decadal retreat information, to infer past glacier ice thickness, which are used to do a glacier-specific calibration of the ice thickness reconstruction, was conducted by creating a generic margin thickness from glacier outlines and DEM differencing. This approach proved to be reasonable for Kersten Glacier, where a more common glacier type was assumed, but seemed to underestimate ice thickness at the Northern Icefield, because of the complex topography.

The poster summarizes the results obtained from the thickness reconstructions and compares them to thickness maps from an existing global consensus estimate. In comparison to our results the consensus estimate shows unrealistically thick values for KG in areas that are meanwhile ice-free. A rough projection on glacier recession based on the generated thickness data agrees with other estimates pointing towards the disappearance of the glaciers between 2040 and 2060.

How to cite: Stadelmann, C., Fürst, J., Seehaus, T., Mölg, T., and Braun, M.: The state of Kersten Glacier and the Northern Icefield on Mt. Kilimanjaro , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9339, https://doi.org/10.5194/egusphere-egu2020-9339, 2020

D2680 |
EGU2020-11403
Frank Paul and Philipp Rastner

Svalbard is dominated by large (often calving) glaciers and ice caps with a strong contribution to global sea-level rise. Due to many surge-type glaciers, large changes of glacier extents are common and determination of their mass balance requires a regular update of their outlines. However, frequent cloud cover prevents accurate repeat mapping. In consequence, the last glacier inventory for Svalbard was compiled from satellite scenes acquired over a period of 11 years, making change assessment and other applications difficult. Due to long-lasting seasonal snow and confusion with large perennial snow patches, the minimum size of this inventory has been set to 1 km2.

Here we present a new glacier inventory for Svalbard that has been compiled at 10 m resolution from two Sentinel-2 scenes that were acquired only two days apart. Sea ice, ice-bergs, lakes and turbid water were wrongly classified as glaciers by the applied band ratio method and manually removed. Debris cover, snow and ice under some clouds but also polluted (very dark) clean ice was not mapped as thresholds were optimized to get snow and ice in shadow properly mapped. These missing regions were manually added. Snow patches were removed with a 5 by 5 majority filter applied to the binary glacier map and a minimum size of 0.05 km2. Outlines from the previous inventory as available in the RGI were used to guide the corrections. After careful comparison, we used the Arctic DEM to derive surface drainage divides and topographic attributes for all glaciers.

The largest challenges for accurate glacier delineation are discrimination of debris-covered glaciers from peri-glacial debris and rock glaciers, handling of attached seasonal or perennial snowfields, and identifying disintegrating tongues of down-wasting and often debris-covered ice masses remaining after a surge. Compared to the previous inventory, the large area gains and losses of surge-type glaciers are remarkable, but area differences result also from a different interpretation of debris-covered glaciers, inclusion of snow-filled couloirs and several new glaciers that were excluded in the previous inventory.

How to cite: Paul, F. and Rastner, P.: Glacier mapping with Sentinel-2 in Svalbard: Challenges when creating a new glacier inventory in the Artic, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11403, https://doi.org/10.5194/egusphere-egu2020-11403, 2020

D2681 |
EGU2020-11059
Philipp Rastner and Frank Paul

Creating glacier inventories from satellite images and a digital elevation model (DEM) has become quasi standard. Besides the specific challenges for glacier mapping, also the selection of the ‘best’ DEM can be difficult. When using it to derive surface drainage divides and topographic information for each glacier, one has to consider the date of acquisition, artefacts, spatial completeness (data voids) and resolution. In general, using different DEMs gives different drainage divides and thus other glacier sizes. Moreover, due to widespread glacier retreat and rapid surface lowering, topographic information from older DEMs is increasingly biased towards too high values.

In this study we analyse seven freely available DEMs for the Arctic region of Svalbard: ALOS AW3D30, two National Elevation Datasets (NEDs), Arctic DEM, TanDEM-X (90 and 30 m products) and the ASTER GDEM2. All individual DEM tiles were mosaicked and re-projected bilinearly to UTM 33 N. Comparisons of topographic data are performed for three test regions: a) stable terrain (off glaciers), b) glaciers in rough topography, and c) flat glaciers and ice caps.

Overlay of drainage divides indicate large area differences on flat ice caps and small ones in rough topography, where mountain ridges are distinct. On the other hand, different spatial resolution results in large differences in rough topography but plays only a minor role for flat topography. Only 2 m elevation differences on stable terrain in flat valley bottoms were detected between the ALOS DEM (79.9m) and the two NEDs (77.9 m). No differences were found between the TanDEM-X 90 / 30 m and the Arctic DEM (all 109. 9 m). The ellipsoid-geoid difference is thus ~30 m in this region.

Mean elevations of glaciers with flat topography or ice caps differ only slightly, but in steeper topography they reach 6 to 8 m. These differences are also due to the different resolution of the DEMs. In all test regions, only small gaps are detected in the Arctic DEM and artefacts are especially present in the ALOS DEM. For this region the ‘best’ DEM is the TanDEM-X DEM.

How to cite: Rastner, P. and Paul, F.: Which DEM to use for glacier inventory applications? The example of Svalbard, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11059, https://doi.org/10.5194/egusphere-egu2020-11059, 2020

D2682 |
EGU2020-15184
Brice Noël, Constantijn Jakobs, Ward Van Pelt, Stef Lhermitte, Bert Wouters, Carleen Reijmer, Willem Jan Van de Berg, and Michiel Van den Broeke

With a maximum in glaciated area below 450 m elevation (peak in the hypsometry), most Svalbard glaciers currently experience summer melt that consistently exceeds winter snowfall. Consequently, these glaciers can only exist through efficient meltwater refreezing in their porous firn layers. Before the mid-1980s, refreezing retained 54% of the meltwater in firn above 350 m. In 1985-2018, atmospheric warming migrated the firn line upward by 100 m, close to the hypsometry peak, which triggered a rapid ablation zone expansion (+62%). The resulting melt increase in the accumulation zones reduced the firn refreezing capacity by 25%, enhancing runoff at all elevations. In this dry climate, the loss of refreezing capacity is quasipermanent: a temporary return to pre-1985 climate conditions between 2005 and 2012 could not recover the meltwater buffer mechanism, causing strongly amplified mass loss in subsequent warm years (e.g. 2013), when ablation zones extend beyond the hypsometry peak.

How to cite: Noël, B., Jakobs, C., Van Pelt, W., Lhermitte, S., Wouters, B., Reijmer, C., Van de Berg, W. J., and Van den Broeke, M.: Low-elevation of Svalbard glaciers drives high mass loss variability, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15184, https://doi.org/10.5194/egusphere-egu2020-15184, 2020

D2683 |
EGU2020-4927
Enrico Scoccimarro and Danile Peano

The front variations of Alpine glaciers show a general retreat over the past 150 years. This glacier retreat, then, has a large impact on many regional sectors, such as hydroelectricity production, river runoff, and touristic sector. In the last decades, glacier retreat in the Alps has been extremely evident due to the pronounced temperature increase affecting these mountains.

Moreover, numerous model studies exhibit a high probability of occurrence of Alpine glacier disappearance by the end of the current century, especially under extreme future climate change conditions.

The Alpine glaciers disappearance is expected to largely influence the Alpine glaciers regions climate, especially in terms of water availability. For this reason, the occurrence of the Alpine glaciers disappearance is enumerated among the climate tipping point.

Given the reduced average glaciers dimension, high-resolution data are needed to investigate the occurrence and the potential impacts of this tipping point. Thus, the EURO-CORDEX dataset over the EUR-11 domain are analyzed in this study.

Alpine glaciers differ under many characteristics, such as elevation, mean aspect, length, and shape. Consequently, a minimal glacier model, which takes into account few glacier features, is used in detecting the occurrence of the Alpine glaciers disappearance. Besides, a simplified surface mass balance model contributes to generalize the tipping point detection and assess the expected water budget changes.

This effort is part of the EU-funded COACCH project.   

 

Keywords

 

Alpine Glaciers, tipping point, water cycle, EURO-CORDEX

How to cite: Scoccimarro, E. and Peano, D.: Alpine glaciers disappearance tipping point: results from EURO-CORDEX models, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4927, https://doi.org/10.5194/egusphere-egu2020-4927, 2020

D2684 |
EGU2020-13068
Matthias Huss, Enrico Mattea, Andreas Linsbauer, and Martin Hoelzle
Numerous models to project the future evolution of mountain glaciers in response to ongoing climate change are available, both at the local and the global scale. However, a suite of partly major simplifications is necessary in these models given the restrictions in data availability. Whereas most models account for the primary feedbacks, such as the snow-ice albedo feedback and the dynamic glacier response in some way, a considerable number of yet poorly understood or less investigated feedbacks is present that might significantly hamper the reliability of current glaciological projections.
 
Here, we present results of a detailed modelling study for the example of Vadret da Morteratsch, Swiss Alps. A surface mass balance model accounting for ice dynamics is forced with downscaled regional climate model output (68 scenarios, CH2018) for the period 2015 to 2100. Various processes are either parameterized or explicitly accounted for. We focus on the use of a fully distributed surface energy-balance approach in comparison to simplified degree-day methods. The relevance of projected changes in different components of the energy balance is assessed using model experiments. In particular, the importance of feedback effects due to (1) the spatio-temporal evolution of supraglacial debris, (2) the formation of new proglacial lakes, and (3) changes in bare-ice albedo and local direct solar irradiance is investigated.
 
We find that the above feedback effects all have a rather small potential to substantially impact on the rates of expected glacier retreat. In some cases, this is unexpected (e.g. for debris coverage and proglacial lakes) but can be explained by compensating processes. We also discuss and visualize the future wastage of Vadret da Morteratsch under the newest generation of climate scenarios, and put these results into context with previous studies, as well as with plans to artificially reduce the rate of glacier mass loss.

How to cite: Huss, M., Mattea, E., Linsbauer, A., and Hoelzle, M.: Modelling future glacier evolution: Which feedbacks are relevant?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13068, https://doi.org/10.5194/egusphere-egu2020-13068, 2020

D2685 |
EGU2020-13289
Marta Chiarle, Roberta Paranunzio, Guido Nigrelli, Giovanni Mortara, Silvia Terzago, Jost von Hardenberg, and Chiara Cardinali

For application purposes (in particular water resources management and planning) it is crucial to rely on accurate predictions of the evolution of glaciers on short time scales (from seasonal to multi-annual).

This is one of the aims of the MEDSCOPE project in the framework of the ERA4CS initiative: seasonal-to-decadal climate forecasts, produced and downscaled by the project, are used to estimate the evolution of glaciers in selected areas of the Western Italian Alps.

For this purpose, empirical glacier models have been calibrated with historical observational data of glacier front fluctuation and mass balance for five glaciers, characterized by different morphology and topoclimatic setting, in the Western Italian Alps. The models will be forced with the seasonal, downscaled forecasts, in order to assess the added value provided by MEDSCOPE to climate services for water management.

How to cite: Chiarle, M., Paranunzio, R., Nigrelli, G., Mortara, G., Terzago, S., von Hardenberg, J., and Cardinali, C.: Forecasting alpine glacier evolution at the seasonal/multiannual scale, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13289, https://doi.org/10.5194/egusphere-egu2020-13289, 2020

D2686 |
EGU2020-3425
Akansha Patel, Ajanta Goswami, Thamban Meloth, and Parmanand Sharma

The understanding of fresh water storage in the Himalayan region is essential for water resource management of the region. As glacier mass balance is a difference between the input and output water storage in a glacier over a period, glacier mass balance can be used as an indirect method to understand the storage. In the northwestern Himalaya, microscale meteorological stations are needed for mass balance estimation due to rugged terrain and complex topography of this region. However, there are only few meteorological stations available in that region. Therefore, in this study, we have developed a new model for glacier mass balance estimation at basinal scale. This model  includes the parameterization of energy balance components viz. albedo, longwave radiation, shortwave radiation, sensible heat, latent heat and heat flux at spatial and temporal scale using earth observation data. The modeling of air temperature is performed using the multi-regression analysis over the Chenab basin of the Indian Himalayas. Simulation is driven with the 16-days Landsat optical and thermal data from 2015 to 2018 that can be used for parameterization of the variable. This model is calibrated and validated with the field data of period 2015-2016. Further, the impact of climatic change and their influence on mass balance was also assessed to understand the future glacier health and mass changes. In contrast to previous temperature index based basin scale models, this model includes most of the energy balance components for better estimation of glacier mass balance. The model can also be used to estimate possible responses of the world’s glaciers to future climate change.

How to cite: Patel, A., Goswami, A., Meloth, T., and Sharma, P.: Development of basinal scale glacier mass balance model: an approach based on satellite observation and energy balance components, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3425, https://doi.org/10.5194/egusphere-egu2020-3425, 2020

D2687 |
EGU2020-18265
Taisiya Dymova, Oleg Rybak, and Viktor Popovnin

Mathematical modeling of surface mass balance (SMB) of mountain glaciers requires appropriate climatic forcing. Normally, meteorological records from the weather stations located as close as possible to the glacier are used for this purpose. In the ideal case, a weather station is located directly on the glacier. Even then, weather records are comparatively short and are hardly applicable for transient simulation of glacier dynamics. Thus, the lack of observations is an obvious obstacle for obtaining reliable simulation results. To overcome it, we suggest to apply a simple stochastic weather generator to emulate synthetic records of surface air temperature, precipitation and other meteorological variables required for calculation SMB by an energy-balance model.

Weather generators have been applied in many geophysical applications for decades, except, paradoxically, for glaciological ones. This is a powerful tool enabling generation of synthetic records which are statistically similar to observations (including probability distribution, standard deviations, autocorrelations etc.).

We report about the work in progress, which aims at elaboration of a reliable methodology for SMB calculation in diverse environmental conditions.

The study was supported by Russian Foundation of Basic Research RFBR (grant Nos. 18-05-00420 and 18-05-60080).

How to cite: Dymova, T., Rybak, O., and Popovnin, V.: Towards elaboration of a surface mass balance model of a mountain glacier using a stochastic weather generator, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18265, https://doi.org/10.5194/egusphere-egu2020-18265, 2020

D2688 |
EGU2020-18937
Alla Turchaninova, Sergey Sokratov, Yury Seliverstov, Dmitry Petrakov, Anton Lazarev, and Ekaterina Bashkova

Glacier mass balance is affected by non-climatic factors such as topography, debris cover and geometric parameters of glaciers themselves, avalanche activity, volcanism, etc. The contribution of snow avalanches to the snow accumulation on a glacier is still among the least studied components of the glacier’s mass balance. We propose a possible approach for the numerical assessment of snow avalanche contribution to accumulation at mountain glaciers. The approach consists on the following steps: terrain analysis; weather data analysis; snow avalanche volume assessment during an analyzed balance year; numerical simulation of snow avalanches using RAMMS; evaluation of snow avalanche contribution to glacier accumulation. The proposed methodology was tested on three glaciers (Batysh Sook, № 354, Karabatkak) with an area up to 6,5 km2 in the Inner Tien Shan and Kolka glacier with an area 1,2 km2 in the Central Caucasus. To evaluate snow avalanche contribution to the winter accumulation, we reconstructed avalanche release zones that were most probably active during the analyzed balance year and corresponding snow fracture height in each zone. The numerical simulations of most probable released snow avalanches during the analyzed year using avalanche dynamics RAMMS software were performed and compared with the field observations and UAV orthophoto images. The outlines of avalanches deposits were realistically reproduced by RAMMS according to the results of field observations. The estimated contribution of snow avalanches to the accumulation on the studied glaciers during the analyzed balance year was as follows: Batysh Sook – 7,4±2,5%; № 354 – 2,2±0,7%; Karabatkak– 10,8±3,6% of the winter mass balance. In strong contradiction to the benchmark glaciers in the Tien Shan, the Kolka glacier demonstrates rapid mass gain in the Caucasus. It might be explained by significant, up to 80% share of avalanche nourishment to glacier mass gain. We note that avalanche-fed glaciers seem to be more stable at current stage of regional warming observed both in the Caucasus and the Tian Shan. The obtained results show the importance of the non-climatic factors for glacier surface mass balance control.

How to cite: Turchaninova, A., Sokratov, S., Seliverstov, Y., Petrakov, D., Lazarev, A., and Bashkova, E.: Non-climatic factors affecting glacier mass balance (on the example of avalanche nourishment), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18937, https://doi.org/10.5194/egusphere-egu2020-18937, 2020

D2689 |
EGU2020-21050
Yuzhe Wang and Tong Zhang

The worldwide glacier is retreating and is expected to continue shrinking in a warming climate. Understanding the dynamics of glaciers is essential for the knowledge of sea-level rise, water resources in high mountain and arid regions, and the potential glacier hazards. Over the past decades, various 3D higher-order and full-Stokes ice flow models including thermomechanical coupling have been developed, and some have opened their source codes. However, such 3D modeling requires detailed datasets about surface and bedrock topography, variable climatic conditions, and high computational cost. Due to difficulties in measuring glacier thickness, only a small minority of glaciers around the globe have ice thickness observations. It is also a challenge to downscale the climate data (e.g., air temperature, precipitation) to the glacier surface, particularly, in rugged high-mountain terrains. In contrast to 3D models, flowline models only require inputs along the longitudinal profile and are thus computationally efficient. They continue to be useful tools for simulating the evolution of glaciers and studying the particular phenomena related to glacier dynamics. In this study, we present a two-dimensional thermomechanically coupled ice flow model named PoLIM (Polythermal Land Ice Model). The velocity solver of PoLIM is developed based on the higher-order approximation (Blatter-Pattyn type). It includes three critical features for simulating the dynamics of mountain glaciers: 1) an enthalpy-based thermal model to describe the heat transfer, which is particularly convenient to simulate the polythermal structures; 2) a drainage model to simulate the water transport in the temperate ice layer driven by gravity; 3) a subglacial hydrology model to simulate the subglacial water pressure for the coupling with the basal sliding law. We verify PoLIM with several standard benchmark experiments (e.g., ISMIP-HOM, enthalpy, SHMIP) in the glacier modeling community. PoLIM shows a good performance and agrees well with these benchmark results, indicating its reliable and robust capability of simulating the thermomechanical behaviors of glaciers.

How to cite: Wang, Y. and Zhang, T.: PoLIM: an open source 2D higher-order thermomechanically coupled mountain glacier flow model, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21050, https://doi.org/10.5194/egusphere-egu2020-21050, 2020

D2690 |
EGU2020-10032
Jakob Abermann, Wolfgang Schöner, and Robert Schjøtt Fausto

Alfred Wegener contributed extraordinarily to early days of scientific explorations in Greenland. Involved in three expeditions, we present unique historical data that is stored at Graz University, where Wegener filled his last academic position until his tragic death in Greenland in 1930. In this contribution we reevaluate data from his last expedition 1929-1931 acquired at the Qaamarujuup Glacier in West Greenland (71°09'N; 51°11'W). Sub-weekly ablation measurements along with air temperature, humidity, pressure, wind and short-wave radiation data exist for two full ablation seasons both near sea level and in 950 m a.s.l.. The 20th Century reanalysis product of the nearest grid-point performs well reproducing air temperature variability. Coincidentally, this expedition was carried out during a very warm period that was in fact comparable to recent years. We compare vertical ablation gradients from the years 1929/1930 obtained at Qaamarujuup in West Greenland with recent observations from the closest PROMICE automated weather station and discuss differences in a centennial perspective. Furthermore, we present a time-series of glacier stages from the little ice age (LIA) maximum up to present and quantify area and volume changes since. The glacier margin was in close proximity (<50 m distance) to the ocean during the LIA maximum, 660 m and almost 3 km horizontal distance from the ocean in 1930 and in 2019, respectively. Such a drastic geometrical change manifests in differing drivers of the glacier boundary layer with the impact of the cooling ocean during summer decreasing with time as the glacier margin’s distance to the ocean increases. We discuss the potential in using historical glacio-meteorological measurements along with a detailed glacier history in order to extract geometrical feedbacks from the climate change signal.

How to cite: Abermann, J., Schöner, W., and Fausto, R. S.: Historical ablation rates and their drivers in Greenland – assessing the potential of the Wegener expedition for modern glaciological research, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10032, https://doi.org/10.5194/egusphere-egu2020-10032, 2020

D2691 |
EGU2020-12902
Michaela Mühl, Bradley R. Markle, Andreas Gschwentner, Charlie Daniels, Ona Underwood, Abigail Lambert, Paola Araya, Jacquelyn Bellefontaine, Brendon Owczarek, Stanley Pinchak, Alf Pinchak, Robert Asher, Chris McNeil, Scott McGee, and Shad O’Neel

Recent temperature history of the Juneau Icefield

 

Mass loss from Alaskan glaciers makes a significant contribution to current sea-level rise. The Juneau Icefield (JIF) of southeast Alaska is one of the world largest, and longest-studied, ice fields, and is currently in a documented state of thinning, retreat, and negative mass balance. The climatological context of this glacier change is critical to understanding its causes, the future of the region, and perhaps that of similar mountain glaciers. Do these changes primarily reflect changes in accumulation or ablation? Are mean air temperatures in the region increasing? If so, during which season, ablation or accumulation, are the changes strongest?

Here we investigate the recent temperature history of the Juneau Icefield, using a combination of reanalysis data and in situ temperature observations from the Juneau Icefield Research Program.  On the whole, we find a significant trend in annual average temperature since the 1950’s of 0.19°C per decade. Interestingly, this warming is entirely a winter-season signal. We find no significant trend in summer-season temperatures, but a winter time trend of nearly 0.5°C per decade, over twice that of the annual average. This pattern is consistent between the reanalysis products and the local temperature observations across the icefield. Using the in situ measurements from stations across the icefield, we find that the magnitude of the winter-season warming (and that of the annual mean warming) depends strongly on surface elevation: the higher the surface elevation the larger the trend in warming. These results have implications for the cause of recent glacier changes. While there is little evidence for a change in ablation-season temperatures, these results point toward changes in both the length of the ablation season and perhaps the phase of winter precipitation. The elevation-dependence of these trends may have further implications for the future stability of the JIF.

How to cite: Mühl, M., Markle, B. R., Gschwentner, A., Daniels, C., Underwood, O., Lambert, A., Araya, P., Bellefontaine, J., Owczarek, B., Pinchak, S., Pinchak, A., Asher, R., McNeil, C., McGee, S., and O’Neel, S.: Recent temperature history of the Juneau Icefield, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12902, https://doi.org/10.5194/egusphere-egu2020-12902, 2020

D2692 |
EGU2020-1844
Ian Lee, Robert Hawley, and Christopher Gerbi

Accelerated melting of glaciers and ice caps has raised serious concerns about sea level rise. As we work towards a solution to address these concerns, it has become a chief priority to rapidly improve predictions of future changes in global ice mass balance. Numerical simulations projecting ice loss have uncovered a strong sensitivity to mechanical and/or rheological weakening of the shear margins of streaming ice. To accurately project sea level rise, future models will require careful treatment of shear margins. This necessitates a deeper understanding of the flow dynamics at shear margins and how streaming flow relates to the constitutive flow law for ice.

 

We developed an open source inexpensive tilt sensor (∼20% the cost of commercial sensors) for studying ice deformation and installed our tilt sensor systems in two boreholes drilled close to the shear margin of Jarvis Glacier, Alaska to obtain kinematic measurements of streaming ice. We used the collected tilt data to calculate borehole deformation by tracking the orientation of the sensors over time. The sensors' tilts generally trended down-glacier, with an element of cross-glacier flow in the borehole closer to the shear margin. We also evaluated our results against flow dynamic parameters derived from Glen's exponential flow law and explored the parameter space of the stress exponent n and enhancement factor E. Comparison with values from ice deformation experiments shows that the ice on Jarvis is characterized by higher n values than that is expected in regions of low stress, particularly at the shear margin (~3.4). The higher n values could be attributed to the observed high total strains coupled with potential dynamic recrystallization, causing anisotropic development and consequently sped up ice flow. Jarvis' n values place the creep regime of the ice between basal slip and dislocation creep. Tuning E towards a theoretical upper limit of 10 for anisotropic ice with single-maximum fabric reduces the n values by 0.2.

How to cite: Lee, I., Hawley, R., and Gerbi, C.: Streaming flow on polythermal mountain glaciers: In-situ observations on Jarvis Glacier, Alaska, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1844, https://doi.org/10.5194/egusphere-egu2020-1844, 2019

D2693 |
EGU2020-5581
Joshua Chambers, Mark Smith, Thomas Smith, Duncan Quincey, Jonathan Carrivick, Lindsey Nicholson, Jordan Mertes, Rudolf Sailer, and Ivana Stiperski

Spatially and temporally distributed values of glacier aerodynamic roughness (z0) are required to improve estimates of glacier melt. z0, representing the topographically-controlled height above the surface where wind speed reaches zero, is shown by empirical studies to be spatially and temporally dynamic, yet, z0 is commonly overlooked as a tuning parameter in models or generalised between surfaces and over time. Indirect estimates of z0 made from microtopographic measurements allow for rapid data collection over large areas but are sensitive to measurement scale, data resolution and detrending technique. The recent proliferation of remotely sensed topographic data from airborne and satellite sources has created a wealth of resources, as yet untapped in this particular field. We present a multi-scale analysis using data collected from Hintereisferner, Austria, with a view to upscaling current methods for estimating 3D microtopographic z0 so that coarser resolution, broader scale data can be used to estimate z0 at the glacier scale. Our extensive dataset covers a spectrum of scales from 5 x 5 m plots (at sub-cm resolution) to scans of almost the whole glacier surface from an in-situ terrestrial laser scanner.

How to cite: Chambers, J., Smith, M., Smith, T., Quincey, D., Carrivick, J., Nicholson, L., Mertes, J., Sailer, R., and Stiperski, I.: A multi-scale investigation of geometrically derived z0 from Hintereisferner, Austrian Alps, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5581, https://doi.org/10.5194/egusphere-egu2020-5581, 2020

D2694 |
EGU2020-11547
Chiara Marchina, Valeria Lencioni, Francesca Paoli, Marzia Rizzo, and Gianluca Bianchini

Glaciers are shrinking due to global warming, resulting in a diminishing contribution of ice- and snowmelt to headwaters with consequences on freshwater ecosystems. The stable isotopic compositions in natural waters (δ18O and δ2H) respond to environmental variation very sensitively and can indicate the change of geographic environment or mark the recharge of runoff (Boral 2019, Zuecco 2019). Thus, stable isotopes have been used as natural tracers to constrain the contributions of different water sources to streamflow, including snowmelt, icemelt and groundwater baseflow (Boral 2019). Within this context, we tested if water stable isotopes are spatio-temporal tracers of: i) water in periglacial habitats, being the isotopic signature of surface water inherited from the snow/icemelt, groundwater, and rainfall; ii) regional (year-specific) meteorological conditions, being the isotopic signature of precipitations affected by air temperature, humidity and aqueous vapour origin, ascribing stable isotopes in the list of the “essential climate variables″ (ECV). In this light, we investigated the ionic and isotopic composition (δ18O and δ2H) of six high altitude streams and one pond in the Italian Alps (Noce and Sarca basins) during the ablation season in 2018. Differences between habitat types (pond, kryal, rhithral, krenal) were detected. More negative values of δ18O and δ2H were recorded in the kryal and glacio-rhithral sites dominated by ice and snowmelt, in early summer. Less negative values were recorded in these sites in late summer and in krenal sites, dominated by groundwater and rainfall inputs. The isotopic results also showed that the complex alpine orography influences the air masses and moist, ultimately resulting in isotopic differences in precipitations of neighbouring, but distinct catchments (Sarca and Noce basins). As average, less negative values were recorded in the Sarca basin, characterized by a higher contribution of precipitation of Mediterranean origin. Finally, isotopic composition of the entire water population appeared to be strongly influenced by the regional climatic anomaly of the year 2018, which was anomalously warm in respect to the historical series 1961- 1990. This study will provide additional clues for the climate-change debate, proposing water isotopes as “essential climate variables″ indicators for assessing change in a warmer future.

 

Keywords: stable isotopes, glaciers, essential climatic variables

 

References:

Boral S., J. Hydrol., https://doi.org/10.1016/j.jhydrol.2019.123983

Zuecco G., Hydrol. Process, https://doi.org/10.1002/hyp.13366.

How to cite: Marchina, C., Lencioni, V., Paoli, F., Rizzo, M., and Bianchini, G.: Monitoring isotopic signature in headwaters to trace environmental changes: an example in the Italian Alps , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11547, https://doi.org/10.5194/egusphere-egu2020-11547, 2020

D2695 |
EGU2020-10150
Joaquín M. C. Belart, Eyjólfur Magnússon, Etienne Berthier, Águst Þ. Gunnlaugsson, Finnur Pálsson, Guðfinna Aðalgeirsdóttir, Tómas Jóhannesson, and Helgi Björnsson

Excluding the three largest ice caps, Icelandic glaciers have, until recently, received limited attention in terms of mass balance observations over the last century. In this study, mass balance estimates from 1945 to 2017 are presented, in decadal time spans, for 14 glaciers (total area 1054 km2) subject to different climatic forcing in Iceland. The mass balances are derived from airborne and spaceborne stereo imagery and airborne lidar, and correlated with precipitation and air temperature by a first order equation including a reference-surface correction term. This permits statistical modelling of annual mass balances and to temporally homogenize the mass balances for a region-wide, multidecadal mass balance study. The mean (standard deviation) mass balances of the target glaciers were −0.43 (0.17) m w.e. a−1 in 1945−1960, 0.01 (0.21) m w.e. a−1 in 1960−1980, 0.10 (0.23) m w.e. a−1 in 1980−1994, −0.98 (0.44) m w.e. a−1 in 1994−2004, −1.23 (0.57) m w.e. a−1 in 2004−2010 and 0.06 (0.35) m w.e. a−1 in 2010−2017. The majority of mass loss occured in 1994−2010, accounting for 22.5±1.6 Gt (1.4±0.1 Gt a−1). High decadal mass-balance variability is found on glaciers located at the south and west coasts,
in contrast to the glaciers located inland, north and northwest. These patterns are likely explained by the proximity to warm (south and west) versus cold (northwest) oceanic currents.

How to cite: Belart, J. M. C., Magnússon, E., Berthier, E., Gunnlaugsson, Á. Þ., Pálsson, F., Aðalgeirsdóttir, G., Jóhannesson, T., and Björnsson, H.: Spatially distributed mass balance of 14 Icelandic glaciers, 1945−2017. Trends and link with climate., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10150, https://doi.org/10.5194/egusphere-egu2020-10150, 2020

D2696 |
EGU2020-18706
Etienne Berthier, Ines Dussaillant, Fanny Brun, and Vincent Favier

The northern Patagonian Icefield (NPI) is the second largest ice mass in Patagonia (3740 km²). Estimation of recent volume changes confirm an acceleration of ice loss in the last decades compared to the mean mass loss since the Little Ice Age. However, Icefield-wide responses at shorter time scales (5-25 yrs) are still poorly documented and not well understood.

We compare five digital elevation models (DEM) acquired between 1975 and 2016 over the NPI: SPOT6 and SPOT7 DEMs for year 2016, SPOT5-HRS DEMs for 2012 and 2005, the Shuttle Radar Topography Mission DEM (SRTM) for year 2000 and the earlier Chilean military institute cartography (IGM) derived from aerial photographs acquired in 1975. We derive cefield-wide mass balances during four different time periods (1975-2000, 2000-2005, 2005-2012, 2012-2016). Our results suggest an acceleration of mass loss from 1975 to 2016. Although error bars are large, we suggest a shift from moderately negative icefield-wide mass balance rates before 2000 (of the order of -0.6 m w.e. yr-1), towards larger mass losses during the first decade of the 21st century(of the order of -0.8 m w.e. yr-1) and even more negative value from 2012 to 2016 (-1.2 ± 0.2 m w.e. yr-1).

But these results must be considered cautiously. The 1975-2000 map of elevation change shows a thickening rate of over 1 m/yr which are not supported by image analysis. We stress the need to construct a revised 1975 NPI topography in order to document the NPI mass balance observations back to 1975 with improved confidence.

How to cite: Berthier, E., Dussaillant, I., Brun, F., and Favier, V.: Multi-temporal mass balance changes of the Northern Patagonian Icefield from 1975 to 2016, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18706, https://doi.org/10.5194/egusphere-egu2020-18706, 2020

D2697 |
EGU2020-11388
Inigo Irarrazaval Bustos, Alejandro Dussaillant, Pablo Iribarren Anacona, Sebastián Vivero, Jorge O'Kuinghtton, and Gregoire Mariethoz

Glacier dynamics are sensitive to the formation and expansion of proglacial lakes. Proglacial lakes development can accelerate glacier retreat rate by flotation of the terminus, formation of a calving front, and increased ice flow. Understanding the impacts of proglacial lakes formation and development, which are reported to be growing in number in Patagonia and other regions, is relevant to improve the understanding and prediction of glacier response to climate change.

This study aims to characterize and monitor recent spatial and temporal changes in the lower section of the Exploradores Glacier (15 km2), located at the northeast section of the Northern Patagonian Icefield. A proglacial lake located at the east margin has been expanding by calving since the early 2000s, and supraglacial ponds located at the front of the glacier could coalesce to form a larger proglacial lake.

We performed repeated unmanned aerial vehicle (UAV) surveys to obtain a series of high-resolution orthoimages (10cm/pixel) and digital elevation models (DEM) of the lower section of Exploradores Glacier. The series consists in 7 orthoimages and DEMs across one year (March 2019 to March 2020), forming in a dataset that is the first of its kind for a Patagonian glacier. The images are processed by photogrammetric technique structure from motion using Pix4D software, and are co-registered using stable off glacier tie-points. Next, the orthoimages are correlated using a feature tracking algorithm (IMCORR) to derive glacier flow velocities. Surface lowering and morphological changes is obtained by DEM differencing analysis. In addition, an aerial photographic archive (Aniya et al. 2017) providing a 20-year observation record is incorporated in the analysis. The results of the imagery analysis are compared with in-situ ablation stakes measurement during the summer season 2019-2020, which indicates downwasting rates up to 100mm/day. This allows estimating rates of proglacial lake expansion at the east margin, supraglacial lakes coalescence, and increase in debris-covered area.

This study contributes to a better understanding of the processes that occur during a relatively short period in a highly transient glacier. Future work will include modelling ice dynamics to better characterize and predict the response of the glacier to the development of proglacial lakes.

How to cite: Irarrazaval Bustos, I., Dussaillant, A., Iribarren Anacona, P., Vivero, S., O'Kuinghtton, J., and Mariethoz, G.: Morphological and ice dynamic changes induced by the formation of proglacial lakes in Exploradores Glacier, Patagonia., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11388, https://doi.org/10.5194/egusphere-egu2020-11388, 2020

D2698 |
EGU2020-13824
Thupstan Angchuk, Allagapan Ramanathan, Arindan Mandal, Mohd Soheb, Somdutta Mishra, and Sarvagya Vatsal

We present the glacio-metrological measurements on the Patsio glacier, located in the Lahaul-Spiti region, Himachal Pradesh, western Himalaya. In-situ annual and seasonal mass balance measurements have been monitored since 2010 and 2012 respectively. Subsequently, an automatic weather station was installed in the summer of 2015. The baseline investigations show a large variability in meteorological conditions during different seasons. Summer was warm and calm, whereas winter is cold and windy with high precipitation, especially snow. Peak ablation months were July and August. Mean annual temperature over the study period was low (-6.3 °C). January recorded as the coldest month and July as hottest corresponding to a mean of -16.8 and 4.28 °C, respectively. Two contrasting wind flow over the Patsio glacier valley was prominent. The persistent katabatic flow was observed during the winter season and up-valley wind in summer. A classic Temperature Index Model was used to estimate the melt from the Patsio glacier, for the years 2016 and 2017. Degree-day factor (DDF) for various components (snow, ice, and debris covered ice) was estimated using field data. High DDFs for snow, ice, and debris-covered ice were observed compared to other studies. The simulated results (snow and ice) were in good agreement with observed data (R2 = 0.88 in 2016 and 0.93 in 2017). Temperature is the main governing factor in inducing the melt. This study gives insight the metrological conditions together with snow and ice melt of Patsio glacier situated in the high and dry region of the Himalaya.

How to cite: Angchuk, T., Ramanathan, A., Mandal, A., Soheb, M., Mishra, S., and Vatsal, S.: Glacio-metrological measurements of Patsio glacier, Himachal Pradesh (India), Western Himalaya, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13824, https://doi.org/10.5194/egusphere-egu2020-13824, 2020

D2699 |
EGU2020-17753
Giovanni Martino Bombelli, Daniele Bocchiola, Federica Camin, and Paolo Maria Ossi

Depiction of glaciers’ dynamics in the high altitudes of Himalaya, and hydrological fluxes therein is often limited, and yet necessary to assess their contribution to overall water budget in the downstream areas. Information about glaciers in these remote regions is often based on satellite data, which routinely document the retreat or advance of ice-covered areas, while volume changes are less easy to quantify, and require local assessment of weather, and hydrology. 
Here, we report investigation of snow accumulation, ice melt, and mass balance of the West Khangri Nup (WKN) glacier (mean altitude 5494 m a.s.l., 0.23 km2), a part of the Khumbu glacier in the Everest region. The glaciers of the area have experienced negative mass balances in the last three decades, and accordingly investigation of their recent, and prospective dynamics seems necessary. 
Weather, glaciological, snow pits, hydrologic, and isotopic data gathered during some field campaigns (2010-2014) on the glacier, and at the EVK2CNR pyramid site are used here to set up the Poli-Hydro glacio-hydrological model, to depict ice and snow melt and hydrological flows, and investigate seasonal snow dynamics on this high region of the glacier.   
Coupling ice ablation data, and Poli-Hydro simulation for ca. 5 years (January 2010-June 2014), we estimated that WKN depleted ca. -10.46 m of ice water equivalent IWE (i.e. annually ca. -2.32 m IWEy-1). Using then snowpack density, and isotopic (δ18O) profiles on the WKN, we demonstrate that local snowpack during field surveys was recent (Fall-Winter 2013-2014), and that significant snow accumulation did not occur recently. Analysis of recent snow cover from LANDSAT images also confirms snow dynamics as depicted. 
We present original data and results, and complement present studies covering glaciers’ mass balance, and investigation of accumulation zones in the Everest region, and the Himalayas, also potentially helpful in the assessment of future dynamics under ongoing climate change.     

How to cite: Bombelli, G. M., Bocchiola, D., Camin, F., and Ossi, P. M.: A field study of mass balance and hydrology of the West Khangri Nup glacier (Khumbu, Everest)., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17753, https://doi.org/10.5194/egusphere-egu2020-17753, 2020