CR2.1 | Glacier monitoring from in-situ and remotely sensed observations
EDI
Glacier monitoring from in-situ and remotely sensed observations
Convener: Michael Zemp | Co-conveners: Bruce Raup, Hrafnhildur Hannesdóttir, Livia Jakob
Orals
| Fri, 28 Apr, 14:00–15:45 (CEST), 16:15–18:00 (CEST)
 
Room L2
Posters on site
| Attendance Fri, 28 Apr, 10:45–12:30 (CEST)
 
Hall X5
Posters virtual
| Attendance Fri, 28 Apr, 10:45–12:30 (CEST)
 
vHall CR/OS
Orals |
Fri, 14:00
Fri, 10:45
Fri, 10:45
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 distribution and changes. Glaciers are observed on different spatio-temporal scales, from extensive seasonal mass-balance studies at individual glaciers to decadal assessments of glacier mass changes and 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. We invite contributions from a variety of disciplines, from tropical to polar glaciers, addressing both in-situ and remotely sensed monitoring of past and current glacier distribution and changes, as well as related uncertainty assessments. A special focus of this session shall be on (i) strengths and limitations of different types of satellite data for regional and global assessments, (ii) achieving a better temporal resolution of regional and global assessments, (iii) how to develop in-situ networks for real-time monitoring of glacier changes, and (iv) advances in studies on local process understanding and how best to combine them with regional to global change assessments.

Orals: Fri, 28 Apr | Room L2

Chairpersons: Livia Jakob, Bruce Raup
14:00–14:05
14:05–14:25
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EGU23-14011
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solicited
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Highlight
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On-site presentation
Simon Gascoin and Etienne Berthier

Summer 2022, in less than a week, two glaciers collapsed. First in Italy on July 3 (Marmolada) then in Kyrgyzstan on July 9 (Juuku pass). The collapse of the Marmolada glacier caused eleven fatalities. In both cases, we immediately requested the tasking of Pléiades satellites to estimate the collapse volumes by photogrammetry. In both cases, the images were acquired three days after the event, and less than one day later we had the first estimates. We found that the Marmolada glacier lost 65,000 ± 10,000 m3. The Jukuu pass glacier lost a volume almost twenty times greater (1,145,000 m3), which remains however much lower than the volumes involved during the collapse of the Aru glaciers on the Tibetan plateau in 2016 (68 and 83 million m3) or the Kolka Glacier in 2002 (130 million m3). From the Marmolada elevation model and orthoimages we could also estimate that the rupture was approximately 80 m wide and 25 m deep.  In the case of the Juuku glacier, the tongue of the glacier collapsed entirely over a width of almost 300 m and the maximum elevation drop reached 50 m.

How to cite: Gascoin, S. and Berthier, E.: Remote sensing analysis of Marmolada (Italy) and Juuku pass (Kyrgyzstan) glacier collapses, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14011, https://doi.org/10.5194/egusphere-egu23-14011, 2023.

14:25–14:30
14:30–14:40
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EGU23-16174
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On-site presentation
Ines Dussaillant, Romain Hugonnet, Matthias Huss, Etienne Berthier, and Michael Zemp

The geodetic method has become a popular tool to measure glacier elevation changes over large glacierized regions with high accuracy for multiannual/decadal time periods. In contrast, the glaciological method provides annually to seasonally resolved information on glacier mass balance, but only for a small sample of the world’s glaciers (less than 1%). Various methods have been proposed to bridge the gap regarding the spatio-temporal coverage of glacier change observations and provide annually resolved glacier mass balances using the geodetic sample as calibration. Thanks to a new globally near-complete (96% of the world’s glaciers) dataset of geodetic mass balance between 2000 and 2020, a global-scale assessment of annual mass changes at glacier-specific level has now become feasible. Inspired by previous methodological frameworks, we developed a new approach to combine the glacier outlines from the globally complete Randolph Glacier Inventory with the mass balance and elevation change observations from the Fluctuation of Glaciers database of the World Glacier Monitoring Service (WGMS). Our results provide a global assessment of annual glacier mass change and related uncertainties for every individual glacier since 1976. The glacier-specific time series can then be integrated into an annually-resolved gridded global glacier change product at any user-requested spatial resolution, useful for comparison with, for example, gravity-based products, calibration or validation of glacier mass balance models operating at a global scale and to improve assessments of glacier contribution to regional hydrology and global sea-level rise. These developments additionally open a new door of opportunity to keep on pushing the frontiers of glacier change observations towards future assessments of global glacier mass changes at increased temporal resolutions.

How to cite: Dussaillant, I., Hugonnet, R., Huss, M., Berthier, E., and Zemp, M.: An annual mass balance estimate for each of the world’s glaciers based on observations., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16174, https://doi.org/10.5194/egusphere-egu23-16174, 2023.

14:40–14:45
14:45–14:55
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EGU23-12612
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On-site presentation
Tobias Bolch, Daniel Falaschi, Atanu Bhattacharya, Lei Huang, and Owen King

Glaciers are crucial sources of freshwater in particular for the arid lowlands surrounding High Mountain Asia. In order to better constrain glacio-hydrological models, annual, or even better, seasonal information about glacier mass changes is highly beneficial. In this study, we test the suitability of very high-resolution Pleiades DEMs to measure glacier-wide mass balance at annual and seasonal scales in two regions of High Mountain Asia (Muztagh Ata in Eastern Pamir and parts of Western Nyainqêntanglha, South-central Tibetan Plateau), where recent estimates have shown contrasting glacier behaviour. We find that the average annual mass balance in Muztagh Ata between 2020 and 2022 was -0.11 ±0.21 m w.e. a-1, suggesting the continuation of a recent phase of slight mass loss following a prolonged period of balanced mass budgets previously observed. The mean annual mass balance in Western Nyainqêntanglha for the same period was highly negative (-0.60 ±0.15 m w.e. a-1 on average), suggesting increased mass loss rates. The 2022 winter (+0.21 ±0.24 m w.e.) and summer (-0.31 ±0.15 m w.e.) mass budgets in Muztag Ata and Western Nyainqêntanglha (-0.04 ±0.27 m w.e. [winter]; -0.66 ±0.07 m w.e. [summer]) suggest winter and summer accumulation-type regimes, respectively. We support our findings by implementing a Sentinel-1–based Glacier Index to identify the firn and wet snow areas on glaciers and characterize accumulation type and demonstrate the potential of very high-resolution Pleiades data to monitor mass balance at short time scales and to improve our understanding of glacier accumulation regimes across High Mountain Asia.

How to cite: Bolch, T., Falaschi, D., Bhattacharya, A., Huang, L., and King, O.: Annual to seasonal glacier mass balance in High Mountain Asia derived from Pléiades stereo images: examples from the Pamir and the Tibetan Plateau, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12612, https://doi.org/10.5194/egusphere-egu23-12612, 2023.

14:55–15:00
15:00–15:10
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EGU23-13870
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On-site presentation
Andreas P. Ahlstrøm, Robert S. Fausto, Jason E. Box, Nanna B. Karlsson, Penelope R. How, Patrick J. Wright, Baptiste Vandecrux, Anja Rutishauser, Kenneth D. Mankoff, William T. Colgan, Michele Citterio, Alexandra Messerli, Anne M. Solgaard, Signe H. Larsen, Niels J. Korsgaard, Kristian K. Kjeldsen, Rasmus B. Nielsen, Derek Houtz, and Signe B. Andersen and the GEUS GlacioLab Team

With temperatures in the Arctic rising rapidly at a rate of 3-4 times the global mean, monitoring the state of the Greenland ice sheet has never been more relevant.

In-situ observations from the Arctic, in particular from the Greenland ice sheet, are scarce due to the cost and difficulty of maintaining instrumentation in the harsh and remote environment. Yet, the fate of the ice sheet concerns 100s of millions of people living in coastal zones worldwide. To gain understanding of the ice sheet processes leading to sea level rise and increase our ability to capture those in climate models, there is an urgent need to collect in-situ observations from the ice sheet surface. Similarly, ground-truthing observations are necessary for validation and calibration of satellite-derived estimates of ice sheet change.

The Geological Survey of Denmark and Greenland (GEUS), along with partner institutions Asiaq and DTU Space, currently operates a combined network of 40 automatic weather stations (AWS) on ice in Greenland, mainly through the Programme for Monitoring of the Greenland Ice Sheet (PROMICE) and the Greenland Climate Network (GC-Net).

GEUS has implemented a new pipeline providing near-real-time hourly weather observations from the PROMICE and GC-Net stations to its users and the World Meteorological Organization (WMO) for use in numerical weather prediction. The satellite-transmitted AWS data is processed and submitted to the WMO via the Danish Meteorological Institute with a latency of 7 minutes after observations are recorded.

Here, we present the recent advances in our AWS instrumentation, data processing and database solution to invite discussion on how we can best meet the community needs for in-situ observations from the ice sheet.

How to cite: Ahlstrøm, A. P., Fausto, R. S., Box, J. E., Karlsson, N. B., How, P. R., Wright, P. J., Vandecrux, B., Rutishauser, A., Mankoff, K. D., Colgan, W. T., Citterio, M., Messerli, A., Solgaard, A. M., Larsen, S. H., Korsgaard, N. J., Kjeldsen, K. K., Nielsen, R. B., Houtz, D., and Andersen, S. B. and the GEUS GlacioLab Team: Recent advances in monitoring surface mass balance of the Greenland ice sheet, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13870, https://doi.org/10.5194/egusphere-egu23-13870, 2023.

15:10–15:15
15:15–15:25
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EGU23-9215
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ECS
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On-site presentation
Livia Piermattei, Fanny Brun, Christian Sommer, Matthias H. Braun, and Michael Zemp

Quantifying glacier elevation and volume changes is critical to understanding the response of glaciers to climate change and related impacts, such as regional runoff and global sea-level rise. Spaceborne remote sensing techniques enable the quantification of spatially distributed glacier elevation changes at regional and global scales using multi-temporal digital elevation models (DEMs). A growing number of spaceborne studies exist to assess glacier elevation changes but they show widespread differences often beyond the error bars. Here, we present the results of a community-based inter-comparison experiment using spaceborne optical (ASTER) and radar (TanDEM-X) sensors to assess elevation changes for selected individual glaciers and regional glacier samples. Using a predefined set of DEMs, participating groups provided their own estimates using various processing strategies.  

For the selected individual glaciers, the results were validated using airborne data. The validation shows that the median of the spaceborne ensemble is biased by a few decimetres per year with a standard deviation of about half a meter per year. An interesting finding is that no sensor and no processing strategy perform significantly better for all experiment sites. At the regional scale, we find that the co-registration of DEMs is the most relevant processing step for an accurate assessment of elevation change. Other corrections such as gap filling, filtering, and radar penetration have less impact in general but can be essential for individual cases. Temporal corrections (i.e. seasonal and annual) can have a great impact; however, they are not yet well resolved by the remote sensing community.

Our study confirms that the currently available spaceborne geodetic assessments result in relatively widespread glacier elevation changes. Therefore, we recommend an ensemble approach of observations from multiple observational sources. Furthermore, there is a need to establish best practices for related uncertainty estimates.

How to cite: Piermattei, L., Brun, F., Sommer, C., Braun, M. H., and Zemp, M.: Observing glacier elevation changes from spaceborne optical and radar sensors, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9215, https://doi.org/10.5194/egusphere-egu23-9215, 2023.

15:25–15:30
15:30–15:40
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EGU23-13794
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ECS
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On-site presentation
Lorenza Ranaldi, Valeria Belloni, Davide Fugazza, and Mattia Crespi

Glaciers are one of the most important indicators of climate change. Monitoring their evolution is, therefore, crucial for safeguarding the Earth’s ecosystem. In this study, exploiting photogrammetric optical satellite processing techniques, we used image pairs from Ikonos-2 and Plèiades-HR satellites to generate Digital Surface Models (DSMs) of Forni Glacier (Ortles–Cevedale group, Italy) and compute its morphological variations between 2009 and 2016. In addition, we used DSMs generated from Unmanned Aerial Vehicle (UAV) acquisitions collected during summer campaigns from 2014 to 2021 for comparison with very high-resolution DSMs on the terminal portion of the glacier including its tongue, which is also the area more affected by morphological changes. To evaluate the glacier height loss, DSMs co-registration was applied to remove DSM biases due to inconsistencies in the georeferencing of the different satellite image pairs. For this purpose, we used the 2016 UAV DSM as a reference, and we co-registered all the optical DSMs to the 2016 UAV DSM using the Nuth and Kaab algorithm. The DSM height differences after co-registration highlighted a final accuracy of one meter. Since optical satellite data have the advantage of providing information on very large areas, we analysed glacier change not only on small areas of Forni Glacier tongue but also on larger regions including parts of the entire glacial apparatus to depict the evolution of the glacier at different altitudes. Results from optical DSMs were consistent with the average annual variation of the glacier suggested by UAV DSMs analysis, confirming an average 5.00 m/y loss on the Forni tongue during 2014-2016.  Furthermore, based on both UAV and optical data, melting trends have highlighted how climate change is causing an acceleration in the melting process, with values averaging 3.3 m/y in the period 2009-2013, 3.8 m/y in 2009-2016 and 4.7 m/y in 2009-2021. With reference to the optical data only, we observed that the intensity of melting varied at different altitudes, with 10 m of maximum variation above 3000 m, and 30 m between 2600-3000 m during 2009-2016. Our results suggested that despite the limitations related to weather conditions (e.g. cloud coverage) and time revisit, high-resolution optical satellite imagery can certainly be used to estimate relevant morphological variations of glaciers in the order of meter/years, offering the opportunity of monitoring large-scale areas.


 

 

 

How to cite: Ranaldi, L., Belloni, V., Fugazza, D., and Crespi, M.: Glacier change monitoring using optical satellite imagery: the case of Forni Glacier, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13794, https://doi.org/10.5194/egusphere-egu23-13794, 2023.

15:40–15:45
Coffee break
Chairpersons: Michael Zemp, Livia Jakob
16:15–16:35
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EGU23-225
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ECS
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solicited
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On-site presentation
Dilara Kim, Mattia Callegari, Tobias Ullmann, and Martina Barandun

Glaciers are an important contributor to the freshwater supply in the Central Asian region. Their response to climate change has profound consequences for the land-use applications, and is thus essential to understand. The collapse of the Soviet Union has interrupted the vast majority of the conducted glacier mass balance observations, which began to re-establish in 2010. The existing data gap, limited spatial resolution of glaciological measurements, and the high heterogeneity of the region limits the use of in-situ data. Mass balance models rely on observation-based calibration and validation data, such as transient snowlines (TSLs), a transition between snow and ice-covered surfaces on a glacier at a given point in time. At the end of the ablation season TSL approximates the equilibrium line. From TSL we can calculate the snow-covered area fraction (SCAF), the area on the glacier surface that is snow covered in relation to the total glacier area. The TSL and SCAF can be mapped from satellite imagery due to the distinctive spectral and structural signature of snow over time. Our approach presented in this contribution is based on the MODIS time-series, harnessing the advantage of long and close-to-daily observations records for the period before high-resolution satellites became available. To resolve the issue of MODIS coarse spatial resolution, we retrieved SCAF from multispectral Sentinel-2 and cloud-independent Sentinel-1 SAR imagery using established workflow. The automatic classification and calculation of SCAF is performed using the cloud computing service of the Google Earth Engine, which makes the entire approach easily applicable on a large number of remote glaciers worldwide. We validated the results independently with Landsat data over selected glaciers in Central Asia. From the  SCAF time-series we analysed changes in various parameters indicative for the atmospheric conditions and its changes  (amongst others the length of ablation period, the minimum SCAF, and the seasonal SCAF changes ) as well as their 20-year trends. Our results provide a unique time series of temporally and spatially high-resolved SCAF estimates giving observation-based information on the heterogeneity of the region’s climatic setting as well as its changes on subseasonal scale. 

How to cite: Kim, D., Callegari, M., Ullmann, T., and Barandun, M.: Sub-seasonal snowline dynamics of glaciers in Central Asia from multi-sensor satellite observations, 2000-2021, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-225, https://doi.org/10.5194/egusphere-egu23-225, 2023.

16:35–16:40
16:40–16:50
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EGU23-13863
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ECS
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On-site presentation
Ugo Nanni, Dirk Scherler, Francois Ayoub, Romain Millan, Frederic Herman, and Jean-Philippe Avouac

Glacier displacement can in principle be measured at the large-scale by cross-correlation of satellite images. At weekly to monthly scales, the expected displacement is often of the same order as the noise for the commonly used satellite images, complicating the retrieval of accurate glacier velocity. Assessments of velocity changes on short time scales and over complex areas such as mountain ranges are therefore still lacking, but are essential to better understand how glacier dynamics are driven by internal and external factors. In this study, we take advantage of the wide availability and redundancy of satellite imagery over the Western Pamir to retrieve glacier velocity changes over 10 days for 7 years for a wide range of glacier geometry and dynamics. Our results reveal strong seasonal trends. In spring/summer, we observe velocity increases of up to 300% compared to a slow winter period. These accelerations clearly migrate upglacier throughout the melt-season, which we link to changes in subglacial hydrology efficiency. In autumn, we observe glacier accelerations that have rarely been observed before. These episodes are primarily confined to the upper ablation zone with a clear downglacier migration. We suggest that they result from glacier instabilities caused by sudden subglacial pressurization in response to (1) supraglacial pond drainage and/or (2) gradual closure of the hydrological system. Our 10-day resolved measurements allow us to characterize the short-term response of glacier to changing meteorological and climatic conditions.

How to cite: Nanni, U., Scherler, D., Ayoub, F., Millan, R., Herman, F., and Avouac, J.-P.: Climatic control on seasonal variations of moutain glacier surface velocity, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13863, https://doi.org/10.5194/egusphere-egu23-13863, 2023.

16:50–16:55
16:55–17:05
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EGU23-15661
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ECS
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On-site presentation
Jacqueline Bannwart, Livia Piermattei, Inés Dussaillant, Lukas Krieger, Dana Floricioiu, Etienne Berthier, Claudia Roeoesli, Horst Machguth, and Michael Zemp

Digital elevation models (DEMs) from the spaceborne interferometric radar mission TanDEM-X hold a large potential for glacier elevation change assessments and monitoring. However, a bias is potentially introduced through the penetration of the X-band signal into snow and firn that can be substantial. The magnitude of this bias has been analysed in some glaciarized regions of the world; still, the knowledge about X-band penetration of TanDEM-X in the European Alps is limited.

In this study, we investigated the unique situation of almost synchronous acquisition of TanDEM-X and Pléiades DEMs over the Grosser Aletschgletscher, complemented with in-situ observations (ground penetrating radar, snow cores, snow pits), all within a four-day period in late winter 2021. The comparison of the TanDEM-X and Pléiades DEM revealed an elevation bias due to radar penetration of up to 8 m above 3400 m. Further, the concurrent in-situ measurements reveal that the signal is not obstructed by the last summer horizon but reaches into perennial firn.

Our study improves our understanding about the magnitude of X-band penetration of TanDEM-X in the Alps and the underlying process with a relevance for glaciology, snow science, remote sensing and the wider geoscience community.

How to cite: Bannwart, J., Piermattei, L., Dussaillant, I., Krieger, L., Floricioiu, D., Berthier, E., Roeoesli, C., Machguth, H., and Zemp, M.: Elevation bias due to penetration of spaceborne radar signal on Grosser Aletschgletscher, Switzerland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15661, https://doi.org/10.5194/egusphere-egu23-15661, 2023.

17:05–17:10
17:10–17:20
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EGU23-4768
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On-site presentation
Hiroto Nagai, Takayuki Nuimura, Masayuki Takigawa, Lavkush Patel, Sourav Laha, Bhanu Pratap, Keiko Konya, Paramanand Sharma, Koji Fujita, Yota Sato, and Akiko Sakai

Surface melting of alpine glaciers is spatially and temporally heterogeneous and is strongly influenced by climatic and non-climatic variables. Especially supra-glacial debris causes significant uncertainty on the ice melting rate with its physical property and thickness. A thick debris layer decrease ice melting rate, whereas a thin layer increase it with its low albedo. Therefore, a scientific method for spatial quantification of debris influences on the melting rate should be established to assess future projection of glacier shrinkage corresponding to the climate change.

Estimating  thermal resistance (TR), which quantifies how hard the ground heat flux (G) travels to ice-debris interface, with remote-sensing data has been attempted in several studies. However, uncertainties caused by the linear temperature gradient have not been resolved, as well as non-negligible underestimation of TR values. Therefore, this study aims to assess TR calculations on multi-spatial and multi-temporal conditions in detail, and discusses the current state of TR estimation and the potential for further improvement.

A study site is defined in Satopanth glacier [30.77°N; 79.40°E], a debris-covered glacier located in Garhwal region, India. Sampling domains of 12 circles with 100-m radius are put with 1-km intervals through the flow line of supra-glacial debris. In addition, four circles of the same size were placed outside the glacier in the lower reaches.

To calculate TR, first, broadband albedo and surface temperature (Ts) are calculated from all available Landsat-8 data in an orbit path [Path 145; Row 39] acquired from 2013 to the present (N= 81). These have a revisit cycle of 16 days. Cloud-covered pixels and frozen pixels (Ts < 0°C) are removed. Second, downward shortwave/longwave radiations and sensible/latent heat flux are collected from a 1-hour resolution product of ERA5. Combining these inputs, considering surface energy budget, G is calculated as a residue of energy flux, and then TR is calculated as Ts (°C) divided by G.

Our result shows a positive correlation that higher Ts leads higher values of G and TR. This trend have no significant difference between debris-covered surface and off-glacier terrains. It suggests that, in most sample areas with relatively thick debris, G does not reach the ice-debris interface. High-gradient inclinations of G versus Ts increase is identified in a lower part of Ts range (0-5°C). It may be caused by heat absorption because of ice mass under relatively thin debris layer, but such inclination is not reflected in TR’s gradient. In the lower Ts surfaces (0-5°C), slightly lower R is estimated for thinner-debris domains. For the thinner debris layer TR might reflects debris thickness. These features in other multiple glaciers will be shown and compared in the presentation.

Our result suggested that maximum debris thickness of G transfer (DTmax) may be defined. Smaller than the DTmax, G transfer may be estimated, whereas larger than the DTmax, G might be zero. In such domain, spatial distributions of ice cliff and supra-glacial pond are more dominant for melting projection. Further assessments might derive a perspective of multiple models for TR estimation according to debris thickness.

How to cite: Nagai, H., Nuimura, T., Takigawa, M., Patel, L., Laha, S., Pratap, B., Konya, K., Sharma, P., Fujita, K., Sato, Y., and Sakai, A.: Toward improvement of satellite-derived thermal resistance for supra-glacial debris, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4768, https://doi.org/10.5194/egusphere-egu23-4768, 2023.

17:20–17:25
17:25–17:35
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EGU23-12724
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On-site presentation
Frank Paul and Philipp Rastner

Glaciers in the tropical Andes of Peru and Bolivia are important but rapidly declining water resources. Precise knowledge of their extent is thus mandatory for calculation of their volume, area changes and mass balance. Due to wrongly mapped seasonal snow, the glacier outlines currently available from the widely used RGIv6 are often too large, resulting in errors for change assessment and volume estimation. Apart from snow cover, also frequent cloud cover and shadows cast by the steep terrain make glacier mapping in this region challenging.

For this study, we have mapped all glaciers in Peru and Bolivia using cloud-free Landsat TM scenes from 1998 and Sentinel-2 scenes from 2020. In both years seasonal snow off glaciers was largely absent. Glacier extents were mapped with a standard band ratio (red/SWIR) and a scene specific threshold value. Wrongly classified lakes and missing debris cover were manually corrected, the latter also by using the very high-resolution satellite images available in the ESRI Basemap. The Copernicus DEM GLO-30 was used to derive new drainage divides and topographic information for each glacier.

In total, we mapped 3586 glaciers larger than 0.01 km2 covering an area of 1747 km2 in 1998. This is 419 km2 or 20% less than the 2166 km2 in RGIv6. As glacier outlines in RGIv6 are from 2000 to 2009 and most area change studies found continuous and strong area decrease over this period, a ‘back-calculation’ of all glacier areas to the year 1998 with an annual shrinkage rate of 1% gives a mean area overestimation of 27% for 1998. This value varies regionally and is smaller in the Cordillera Blanca and much larger (>50%) in other regions. The related modelled glacier volumes for these regions are thus also overestimated. From 1998 to 2020 glaciers have lost 23% of their area (-1% per year).

How to cite: Paul, F. and Rastner, P.: Glacier extents in Peru and Bolivia are overestimated in RGIv6 by 27%, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12724, https://doi.org/10.5194/egusphere-egu23-12724, 2023.

17:35–17:40
17:40–17:50
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EGU23-12903
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On-site presentation
Monitoring glacier fade out in Austrian Eastern Alps
(withdrawn)
Andrea Fischer, Martin Stocker-Waldhuber, Lea Hartl, Kay Helfricht, Andreas Gschwendtner, Bernd Seiser, and Giulia Bertolotti
17:50–17:55
17:55–18:00

Posters on site: Fri, 28 Apr, 10:45–12:30 | Hall X5

Chairperson: Bruce Raup
X5.266
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EGU23-15715
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ECS
Hrafnhildur Hannesdóttir, Oddur Sigurðsson, Snævarr Guðmundsson, Joaquín M.C. Belart, Ragnar H. Þrastarson, Finnur Pálsson, Eyjólfur Magnússon, and Tómas Jóhannesson

A national glacier outline inventory for several different epochs since the end of the Little Ice Age (LIA) in Iceland has been created with input from several research groups and institutions, and has been submitted to the GLIMS (Global Land Ice Measurements from Space, nsidc.org/glims) database, where it is openly available. The glacier outlines have been revised and updated for consistency and the most representative outline chosen. The maximum glacier extent during the LIA was not reached simultaneously in Iceland, but many glaciers started retreating from their outermost LIA moraines around 1890. The total area of glaciers in Iceland in 2021 was ~10,300 km2. The total glacier area has decreased by ~2300 km2 since the end of the 19th century and by ~830 km2 since ca. 2000. During the first two decades of the 21st century, the decrease rate has on average been ~40 km2 a–1. In this period, some tens of small glaciers have disappeared entirely. Temporal glacier inventories are important for climate change studies, for calibration of glacier models, for studies of glacier surges and glacier dynamics, and they are essential for better understanding of the state of glaciers. Although surges, volcanic eruptions and jökulhlaups influence the position of some glacier termini, glacier variations have been rather synchronous in Iceland, largely following climatic variations since the end of the 19th century.  The glacier outlines are also available on a new glacier web portal (www.islenskirjoklar.is), together with measurements of frontal positions and mass balance and numerous photographs of glaciers at different times. The photographic glacier archive will be updated through systematic photographic surveys, including rephotography of historical photos, based on a collaboration of the Iceland Glaciological Society and Extreme Ice Survey. This website, which is intended for scientists, students and lay people alike, is a joint effort of institutions involved in glacier research in Iceland and the Iceland Glaciological Society. It will serve as a powerful tool for outreach on glacier and climate change in Iceland. The glacier inventory is planned to be updated every other year in the future as part of regular monitoring of glacier changes in Iceland. Furthermore, the larger ice caps will be divided into ice-flow basins along the ice divides of individual outlet glaciers determined from ice-surface DEMs, which will allow for more detailed analysis of area variations with time.

How to cite: Hannesdóttir, H., Sigurðsson, O., Guðmundsson, S., Belart, J. M. C., Þrastarson, R. H., Pálsson, F., Magnússon, E., and Jóhannesson, T.: Glacier changes in Iceland since the Little Ice Age maximum - glacier outlines, terminus measurements and photographic evidence, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15715, https://doi.org/10.5194/egusphere-egu23-15715, 2023.

X5.267
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EGU23-629
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ECS
Nidhiya Jose, Anil Kulkarni, Satheesh Sk, and Sajeev Krishnan

Understanding water resources' long-term availability under varying climatic conditions is vital for water security and adaptation strategies. Due to increased temperature and changes in precipitation patterns, the Himalayan glaciers undergo rapid mass loss. The extent of glaciation has varied considerably since the global Last Glacier Maxima (LGM), ~18-24 ka. Moraine studies provide a better understanding of glaciation’s paleo-extent and timing. This work investigates the extent of glaciation and volume in the Baspa basin during the global LGM. We reconstruct the extent and volume using different remote sensing techniques, including the laminar flow method (HIGHTIM), Topo to Raster tool, Volume – Area scaling, and polygon area method. These methods are applied on 61 glaciers in the basin, considering glacial geomorphology and topographic parameters of the terrain. The glacier boundary and moraines were delineated using Landsat 8 satellite image and high resolution google earth images. The current spatial distribution of ice thickness and volume was estimated using the HIGHTHIM model. Further, the ice thickness was extrapolated to the moraine area using the Topo to Raster tool of ArcGIS, with the help of Cartosat DEM to estimate paleo glacier volume. On smaller glaciers (area<1km2), the current and paleo volume was estimated using the volume-area scaling equation. The glaciated area covers about 161.3 ± 8 km2 and the moraine area is calculated as 49.3 ± 0.46 km2. The estimate suggests ice volume at LGM is 18.71 km3 and the current volume is 8.51 km3, i.e., about a 52% loss in ice volume from LGM. We propose estimating the mass loss in the current decades, which will help understand the acceleration of mass loss under global warming conditions.

How to cite: Jose, N., Kulkarni, A., Sk, S., and Krishnan, S.: Estimation of paleo-extent and volume of glaciers in the Baspa basin, India, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-629, https://doi.org/10.5194/egusphere-egu23-629, 2023.

X5.268
|
EGU23-12237
|
ECS
Examination of ITS_LIVE ice velocity dataset for analysis of alpine glaciers in High Mountain Asia
(withdrawn)
Emma Marshall, Summer Rupper, and Rick Forster
X5.269
|
EGU23-898
|
ECS
|
Jared Magyar, Anya M. Reading, Ross J. Turner, and Sue Cook

This work aims to contribute to progress in the detection of hidden or transient hydrological events. Passive seismic methods offer high temporal resolution and the ability to monitor seismic sources hidden from direct view, making it an ideal candidate to complement other in-situ and satellite methods in these cases. The dynamics of a glacier can be greatly affected by its hydrological system, whether this be through water mediated ice fracturing, or the influence the water has on friction at the ice-bed interface. Effective detection of moving meltwater is therefore of great interest for anticipating future glacier changes and sensitivities.

To effectively infer any hidden process from the observed seismic waveforms, we require a physically rigorous modelling framework. Our work therefore combines hydrodynamic models depicting meltwater flow with seismic wave propagation methods to produce synthetic seismograms. The hydrodynamic model of choice is smoothed particle hydrodynamics (SPH). This is a full, three-dimensional computational fluid dynamics method, meaning we can make minimal assumptions on the exact seismogenic mechanism prior to simulation. SPH has the capacity to capture a broad range of signal-generating processes that may prove to be of interest for modelling meltwater flow, such as fluid-solid impact events, free-surface behaviour (e.g., wave breaks), and some forms of turbulence. Beyond the modelling of complex flow, SPH also allows a simple implementation of arbitrarily shaped solid boundaries and the computation of force of the water on these boundaries; a necessary output for waveform simulation.

We propose a correspondence between different types of meltwater flow and the attributes of the waveforms they produce, as a step towards better detection and characterisation of hidden and short-lived events. Across a diverse set of model geometries and flow types, we anticipate the collection of synthetically generated signals will be useful for categorising archived and real-time signals according to a mechanistic process using unsupervised machine learning methods in ongoing work.

How to cite: Magyar, J., Reading, A. M., Turner, R. J., and Cook, S.: Simulation of water-induced seismic waveforms in glaciers through hydrodynamic modelling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-898, https://doi.org/10.5194/egusphere-egu23-898, 2023.

X5.270
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EGU23-913
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ECS
Ross J. Turner, Jared Magyar, Sue Cook, and Anya M. Reading

We present an analytic framework to model seismic body waves due to supraglacial, englacial or subglacial flows in solid ice based on a smoothed particle hydrodynamic (SPH) simulation. Consisting of two parts, i) hydrodynamic modelling and ii) seismic wave propagation, the flexible framework allows for a pre-existing fluid simulation to be supplied to generate synthetic seismic signals. The field of glacier-related seismology has seen rapid development in recent years, with an expanded availability of passive seismic datasets that contain records of seismic disturbances generated by glacier processes. Some of these processes, such as basal slip and crevasse propagation, have mechanisms with plate tectonic deformation counterparts, however, many glacier signals are generated by moving melt water. This contribution aims to inform the interpretation of such signals.

Our approach tracks the trajectories of fluid particles near the water-ice interface, as recorded in standard simulation outputs, to create a catalogue describing the energetics of each collision. We illustrate the capability of this framework using four end-member cases of water flow along surface channels with different geometries. Seismic signals are simulated at a variety of locations around the channel based on the impulse of the database of simulated collisions. We consider the change in character of the seismic waveforms by modelling frequency-dependent attenuation and weak dispersion in the glacial ice, in addition to the standard geometric spreading. The acceleration time series produced in this work are invariant to the temporal and spatial resolution of the hydrodynamic simulation, provided more than some minimum resolution is used. These time series may be converted to velocity or displacement for comparison with observed seismic signals.

Investigating the seismic waves generated for our four channel geometries, we find distinct waveform envelope shapes with different first and later amplitude peaks matching initial and subsequent collisions of the melt water surge with the supraglacial channel walls. The change in waveform character with distance is also captured such that the character attributes due to the process and the those due to the propagation effects may be understood. The flexibility inherent in the model framework will allow for the generation of the seismic signals from simulations of a variety of different water flow geometries including simple 3D channels into and through a glacier. We make the code available as an open source resource for the polar geophysics community with the aim of adding to the toolbox of available approaches to inform the potential future seismic monitoring of melt water movement and related glacier processes.

How to cite: Turner, R. J., Magyar, J., Cook, S., and Reading, A. M.: Analytical framework to model seismic signals from fluid particle collisions in hydrodynamic simulations of glacier melt water, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-913, https://doi.org/10.5194/egusphere-egu23-913, 2023.

X5.271
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EGU23-6296
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ECS
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Enrico Mattea, Horst Machguth, Etienne Berthier, and Martin Hoelzle

In situ monitoring of glacier mass balance – through a network of reference sites – is essential to improve process understanding and detect changes, as well as provide calibration and validation for local and large-scale modeling and remote sensing studies. Still, the interpretation and representativeness of measured mass balances can be affected by unsteady glacier flow dynamics, from minor pulsations to extreme surges. Such events can alter mass balance gradients and apparent trends; englacial water storage associated with glacier surges can lead to biases in high‑resolution geodetic assessments, and in situ measurements can be disrupted by surface changes during rapid ice movement. At the same time, mass balance and its perturbations can exert multiple influences on glacier dynamics, from an indirect control on surge frequency to the direct triggering of instabilities and propagating waves. So far, a very small number of glaciers worldwide has seen combined long-term observations of mass balance and unsteady ice flow, limiting understanding of their interaction.

Here, we investigate the flow dynamics of the Abramov glacier (Pamir-Alay, Kyrgyzstan), whose measured mass balance series is one of the longest in Central Asia. We use multi-sensor optical remote sensing, including the recently released SPOT World Heritage archive as well as ASTER, IRS-1C/D and RapidEye data, to augment the Landsat record over the past 25 years. Through a dense series of digital elevation models and orthoimages, we quantify a front advance over 2000‑2005 at sub‑seasonal resolution. While the event was not observed in situ, negative mass balances in the preceding decades support an interpretation in terms of unstable ice dynamics. Moreover, asynchronous front advances on several neighboring glaciers reveal a high prevalence of unsteady ice flow in the region. We compare the Abramov advance to a previous surge of 1972/73, which was well documented with extensive in situ measurements but was virtually unknown outside Soviet glaciology. Both events do not fit well within the traditional surge models of hydrological or thermal switch, similar to previous observations in the Pamir-Karakoram.

At present, the west branch of the Abramov glacier is undergoing a slow, regular and widespread inter‑annual speed-up. In the light of continued surface thinning and front retreat, the current evolution likely represents the build-up phase to the next episode of dynamic instability.

How to cite: Mattea, E., Machguth, H., Berthier, E., and Hoelzle, M.: Minor pulsations of Abramov glacier (Kyrgyzstan) observed with multi-sensor optical remote sensing, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6296, https://doi.org/10.5194/egusphere-egu23-6296, 2023.

X5.272
|
EGU23-8711
Bas Altena and Francesco Nattino

The free and open data policy of the Landsat legacy and the Sentinel-2 satellite constellation have enhanced our knowledge considerably. This enrichment is due to an increase in spatial spread; from glacier change at targeted glaciers, to a coverage at regional or global scale. Procedures for snow cover mapping and glacier outline product generation from such multi-spectral data are well matured. Though more potential is present for glacier specific information in such data sources.

Recently several studies presented the capabilities of elevation change extraction via shadow cast detection. Though these are at the proof of concept stage, as many steps are based on heuristics and manual adjustments/measurements.

Here we present a fully automatic pipeline which is based on an open source library, which we developed. The emphasis of this code base, which we named dhdt, is focused on large scale processing. Hence, all steps are fully automatic and structured so distributed processing is possible. It generates spatial temporal elevation changes, over small mountain glaciers. We hope, this will advance the glaciological community forward, giving a new instrument in its toolbox.

How to cite: Altena, B. and Nattino, F.: dhdt: a Python library to transform shifting shadows to glacier elevation change, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8711, https://doi.org/10.5194/egusphere-egu23-8711, 2023.

X5.273
|
EGU23-11141
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ECS
Franziska Mayrhofer, Bernhard Grasemann, and Martin Schöpfer

Time-lapse photogrammetry in conjunction with high-resolution digital elevation models is used to quantify the surficial velocity field and the ablation of the Pasterze, a rapidly retreating alpine valley glacier in Austria. Three automatic time-lapse cameras were installed along the orographic left valley flank, c. 150 m above the glacier’s surface, to monitor retreat and ablation from July to September 2020. Although time-lapse photogrammetry offers spatial and temporal high-resolution data, the various processing steps to calculate the glacier’s velocity field are challenging. Digital image correlation of the time-lapse series photos is achieved using a published Python library (How et al. (2020) PyTrx: a Python-based monoscopic terrestrial photogrammetry toolset for glaciology. Frontiers in Earth Science 8:21, doi:10.3389/feart.2020.00021), which was adapted for the Pasterze data set. Typical time intervals for the digital image correlation were two to ten days. Factors that hamper computing flow velocities from time-lapse series photos alone are low contrast of the glacier’s surface and ablation rates exceeding the horizontal flow velocity. The latter problem is solved with the aid of two high-resolution digital elevation models (DEMs), which were calculated using 790 drone images from flight missions on July 13 and September 15 2020. The photogrammetric (Structure from Motion) software Agisoft Metashape (v. 1.8.4) is used to calculate the two DEMs from dense point clouds with a resolution of 5 cm/pixel. Linear interpolation of the glacier’s elevation between the July and September DEM was used to provide an approximate surface for a given date within the monitoring period. With this additional processing step, we can project tracked pixels from the digital image correlation process on an adapted DEM, which reflects the absolute height on a certain date best. Our workflow illustrates that time-lapse series photos taken obliquely to the glacier’s surface can be used to compute the surficial velocity field with the aid of digital elevation models that yield the glacier’s surface at the beginning and at the end of the monitoring period. In fact, the glacier’s velocity field computed in that fashion is consistent with direct measurements from a sparse network of stakes and mapped structures.

How to cite: Mayrhofer, F., Grasemann, B., and Schöpfer, M.: Quantification of glacier flow velocities using time-lapse photogrammetry in conjunction with high-resolution digital elevation models, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11141, https://doi.org/10.5194/egusphere-egu23-11141, 2023.

X5.274
|
EGU23-13721
|
ECS
Runoff impact on ice velocities in Southwest Greenland
(withdrawn)
Paul Halas, Basile de Fleurian, Jeremie Mouginot, and Petra Langebroek
X5.275
|
EGU23-15647
|
ECS
Signe Hillerup Larsen, Anja Rutishauser, Daniel Binder, Niels Korsgaard, Bernhard Hynek, and Michele Citterio

In situ glaciological monitoring of A. P. Olsen Ice Cap in NE Greenland has been ongoing since 2008. The monitoring effort is part of the Greenland Ecosystem Monitoring (GEM) programme at Zackenberg research station. The monitoring includes: Three automatic weather and ablation stations along a transect, manual stake observations upon every visit in April, ground based radar profiles of last year snow accumulation and geodetic mass balance from satellite based observations. Here we present an overview of all glaciological monitoring data, and use the dataset to estimate the mass balance of A. P. Olsen over the past 13 years.

How to cite: Hillerup Larsen, S., Rutishauser, A., Binder, D., Korsgaard, N., Hynek, B., and Citterio, M.: Glaciological monitoring at A. P. Olsen Ice Cap in NE Greenland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15647, https://doi.org/10.5194/egusphere-egu23-15647, 2023.

X5.276
|
EGU23-16473
Anne Solgaard, Anders Kusk, Signe Hillerup Larsen, Kenneth Mankoff, and Robert Fausto

We present the Programme for Monitoring of the Greenland Ice Sheet (PROMICE) ice velocity product, which is a time series of ice velocity mosaics derived using offset tracking on Sentinel-1 SAR data.  The time series starting in January 2016 is continuously updated with a new mosaic every 12 days and is posted at 500 m grid resolution. Within PROMICE, the ice velocity product is used directly as input to estimate the solid ice discharge from the Greenland Ice Sheet as well as to study ice dynamic processes on seasonal and multi-annual time scales. Recently, we have made changes to the processing chain due to spurious cases of slow down detected in a few glaciers in Southeast Greenland. In this contribution, we discuss how this was resolved as well as other recent improvements to the product.

How to cite: Solgaard, A., Kusk, A., Hillerup Larsen, S., Mankoff, K., and Fausto, R.: Monitoring the flow of the Greenland Ice Sheet: The PROMICE ice velocity product and recent updates, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16473, https://doi.org/10.5194/egusphere-egu23-16473, 2023.

X5.277
|
EGU23-3941
|
Susana del Carmen Fernandez Menendez, Javier Fernandez Calleja, Ruben Muñiz Sanchez, Jaime Otero Garcia, and Francisco Navarro Valero

Snow and ice albedo play a crucial role in the mass losses from the NW Antarctic Peninsula and the South Shetlands Islands since absorption of solar radiation is the largest energy source for surface melt in the cryosphere. Snow albedo exhibits a large variation at different time scales (hours, days, seasonal, long-term trend). It has been established that the thickness of the snow/ice layer that affects the albedo varies from 20 cm to 50 cm.   The surface geomorphology of this layer exerts a strong control in the snow albedo evolution over a day because they affect the amount of solar energy received, and the exposure to prevailing winds. In order to discover patterns of variation between snow albedo and surface geomorphology over Hurd Peninsula glaciers at metric scales, we used four DEMs (1957,2000, 2013 and 2019) of 1 m of spatial resolution. In the four DEMs topographical variables (altitude, slope, plan and profile curvature, aspect) and indexes (diurnal differential heating, wind exposition, roughness index) were calculated using QGis_Gdal_SAGA tools.  Because of the high spatiotemporal variability of the snow cover, the albedo data obtained from fixed stations provide a partial picture of the actual field behaviour.  In order to obtain spatially distributed albedo measurements over Hurd Peninsula glaciers, we designed a portable albedometer. The device consists of two pyranometers, one facing the sky and another facing the ground at 1,20m above the ground, working together with a GNSS. The dataloggers of each pyranometer were set up to take a measurement every 5 seconds. Using this equipment, in January of 2018 and 2019 we surveyed the glaciers of Hurd Peninsula along the same tracks but under different weather conditions (fog, clear sky, clouds and clearings). The population of albedo data obtained with this method was about 800 measured points per track per day.  Using QGis we obtained the values of topographical variables and indexes for all the albedo points. Lineal correlations between albedo and topographical variables and indexes were explored. The R2 was especially high in the tracks performed during open sky days. There are not significant correlations between DTMs variables and albedo data in tracks performed in foggy days. Moreover, we built a Linear Regression Model (forward stepwise) of open_sky day’s albedo with Adjusted R²= 0.86 and Std. Error of estimate: 0.00428 with diurnal differential heating_2019, altitudes (1957, 2000, 2013), slope_2019 and convexity_2019 as predictive variables. To estimate the surface albedo all across Hurd Peninsula extending linear models using QGis. Also, we calculated the DTM of 1957-2019 altitude changes in meters (Minimum=-32.694, Maximum=53.188, Mean=7.959, StdDev=10.526), which shows strong correlation with albedo of all open sky tracks.  We interpreted these results in relation to the density, structure and state of metamorphism of the snow cover that could represent the layer of snow that affects the albedo in Hurd Peninsula glaciers. The preliminary results seem to indicate that the surface melting intra-annual variability of the Hurd Peninsula glaciers, registered in the glacier surfaces geomorphology, exerts a strong influence on the current albedo.

How to cite: Fernandez Menendez, S. C., Fernandez Calleja, J., Muñiz Sanchez, R., Otero Garcia, J., and Navarro Valero, F.: On-site albedo data and their relationship to the long-term evolution of surface morphology in glaciers of Hurd Peninsula, South Shetland Islands, Antarctica, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3941, https://doi.org/10.5194/egusphere-egu23-3941, 2023.

X5.278
|
EGU23-16573
Liliya Dimitrova, Gergana Georgieva, and Vasil Gourev

Livingston Island is one of the eleven islands of the South Shetland Archipelago which is separated from the Antarctic Peninsula by Bransfield Strait and from South America by the Drake Passage. The South Shetland Islands, where the Bulgarian Antarctic Base is located, is characterized by complex geodynamics, including: subduction zones, zones of splitting of the old crust and arising of a new crust, numerous volcanoes. The most of the territory of the Island is coated by permanent snow cover and glaciers. In recent decades, a number of scientific institutions have been working on projects related to the study of various aspects of the seismic regime and the structure of the Еarth's crust in the region of the South Shetland Islands and Antarctica in general, as well as the state and dynamics of the ice sheet. However, this region of the Earth remains still unexplored. Harsh climatic conditions are a serious obstacle for conducting long-term research. Bulgarian scientists from Sofia University "Sv. Kliment Ohridski" and the National Institute of Geophysics, Geodesy and Geography of the Bulgarian Academy of Sciences have been studying the seismicity of the Livingston Island region and the behavior of the glaciers near the Bulgarian Antarctic Base within the framework of three scientific projects since 2014. The projects are funded by the Bulgarian Scientific Fund and National Center for Polar Studies.

One of the aim of the projects is to study the activity of the glaciers during different seasons by combining seismic and GNSS measurements. Seismic registration was carried out by the seismic station LIVV installed previously as temporary station and later developed as a year-round one. GNSS measurements were carried out at certain points on the surface of the glacier Balkan. The resulting estimates of the speed of glacier movement at these points were interpreted in conjunction with the seismic data, thus making an initial attempt to determine the nature of the recorded icequakes. The relationship between seismic activity in the glacier and the change in the temperature of the environment during the astral summer and the astral winter was studied.

The study of the seismicity and ground structure of Livingston Island and the surrounding area have been carried out using the data recorded by the Broadband seismic equipment of the LIVV station, applying a software code developed for this purpose.

Investigating seasonal variations in seismic noise is another goal of the projects. The recorded seismic noise provided information on the condition and behavior of the seismic equipment throughout the recording period, as well as on the sources of seismic noise and their influence on the recording capabilities of the station.

How to cite: Dimitrova, L., Georgieva, G., and Gourev, V.: Exploring seismicity and ice cover of Livingston Island - research projects, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16573, https://doi.org/10.5194/egusphere-egu23-16573, 2023.

X5.279
|
EGU23-16855
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solicited
|
Highlight
Shfaqat Abbas Khan, William Colgan, Thomas Neumann, Michiel van den Broeke, Kelly Brunt, Brice Noël, Jonathan Bamber, Javed Hassan, and Anders Bjørk

The Arctic is warming more rapidly than the rest of the world. This warming has had an especially profound impact on Greenland’s ice cover. Only 4% of Greenland’s ice cover are small peripheral glaciers that are distinct from the ice sheet proper. Despite comprising this relatively small area, these small peripheral gIaciers are responsible for 11% of the ice loss associated with Greenland’s recent sea-level rise contribution. Using the satellite laser platforms ICESat and ICESat-2, we estimate that ice loss from these Greenland glaciers increased from 27±6 Gt/yr (2003–2009) to 42±6 Gt/yr (2018–2021). We find that the largest acceleration in ice loss is in North Greenland, where we observe ice loss to increase by a factor of four between 2003 and 2021. In some areas, it appears that recent increases in snowfall at high altitudes have partially counteracted recent increases in melt at low altitudes. While many recent Greenland ice loss assessments have focused on only the ice sheet, the recent sharp increase in ice loss from small peripheral glaciers highlights the importance of accurately monitoring Greenland’s small peripheral glaciers. These small peripheral glaciers appear poised to play an outsized role in Greenland ice loss for decades to come.

How to cite: Khan, S. A., Colgan, W., Neumann, T., van den Broeke, M., Brunt, K., Noël, B., Bamber, J., Hassan, J., and Bjørk, A.: Accelerating ice loss from peripheral glaciers in North Greenland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16855, https://doi.org/10.5194/egusphere-egu23-16855, 2023.

Posters virtual: Fri, 28 Apr, 10:45–12:30 | vHall CR/OS

Chairperson: Hrafnhildur Hannesdóttir
vCO.1
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EGU23-11201
|
ECS
Juan de Dios Fernandez, Brandon Fajardo, Yadira Curo, Mayra Mejia, Gladis Celmi, Danny Robles, and Alberto Castañeda

In Peru, there are 20 glacial mountain ranges that in almost 60 years have lost 54% of their glacial coverage. The accelerated glacial recession due to climate change raises the need to know the levels of retraction of the glacier surface efficiently and reliably. During the preparation of the last inventory by the National Institute for Research in Glaciers and Mountain Ecosystems (INAIGEM), it was identified that carrying out the inventory faces challenges, such as differentiating between temporary snow and glacier ice, especially in areas with complex meteorological characteristics. like the Cordillera Blanca (Peru). Due to the Peruvian Andes’ geographical and climatic complexity, satellite images usually show cloudiness and temporary snow, even in the dry season (April to November). In this way, the objective is to obtain an ideal image with annual glacier coverage with minimal snow reflecting the current glacier surface. For this, the script "Normalized Differentiated Snow Index - minimum NDSI" was developed, which analyzed the Sentinel-2A image catalog of the year 2020 and delimited the glaciers of the Huascarán and Huandoy systems in the Cordillera Blanca.

The proposed methodology aims to evaluate the techniques for generating glacier cover, which allows the proposed objective to get the minimum glacier area. Three glacier cover generation techniques were evaluated: mosaic, medium, and minimum. For the mosaic and average reductions, the algorithm applied a cloud filter to the Sentinel-2A image set and calculated the NDSI for the month that was lowest in the historical average from Landsat 5, 7, and 8 images (1990-2020), applying a threshold of 0.4 and exporting the results with mean and mosaic reduction, respectively. While the minimum NDSI was calculated annually (2020) from Sentinel-2A images, with a cloud filter to which the reduction by minimums is applied, within the same area of interest, applying the threshold of 0.4 and exporting the results in raster format. Finally, the three results were evaluated in terms of the percentage of overestimation concerning glacier coverage in 2016.

The results reveal that the Huascarán and Huandoy glacier systems present a lower NDSI value during August and October, with standard deviations of 0.12 and 0.14, respectively. The glacier cover generated by the minimum NDSI was compared in the percentage of overestimation (m2) concerning 2016 with the average and mosaic NDSI, finding as a result that the minimum glacier cover, for the year 2020, evidences a lower percentage of temporal snow in the Huascarán system between 157.12% and 76.84% less than the filtering methods: average and mosaic. Likewise, in the Huandoy system, there is evidence of a lower percentage of temporary snow between 205.91% and 191.65% less than the average and mosaic methods. Finally, it is necessary to indicate that the developed algorithm has improved the obtaining of glacier coverage from the inventory developed by INAIGEM and reduces the overestimation of glacier coverage due to temporary snow.

How to cite: Fernandez, J. D. D., Fajardo, B., Curo, Y., Mejia, M., Celmi, G., Robles, D., and Castañeda, A.: Proposed algorithm for the identification of glacier cover from Sentinel-2A images, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11201, https://doi.org/10.5194/egusphere-egu23-11201, 2023.

vCO.2
|
EGU23-12494
|
ECS
Increasin Melt Season Duration : Barashigiri Glacier
(withdrawn)
Prateek Sharma and Manabendra Saharia