CR7.2

EDI
Coupled modelling in the polar regions & Facilitating remote sensing applications across the terrestrial Arctic

THIS SESSION IS A MERGE OF 2 SESSIONS. PLEASE CHECK PUBLIC INFORMATION FOR MORE INFORMATION.
BELOW YOU FIND BOTH SESSION DESCRIPTIONS
Coupled modelling in the polar regions
In recent decades, the climate in the polar regions has undergone dramatic changes. Quantifying the individual contributions of Earth system components (cryosphere, ocean, atmosphere, and land) to the observed changes is challenging due to feedback between the components. Examples include (but are not limited to) ice shelf – ocean interactions (through basal melting and cavity geometry evolution) and elevation feedback (through surface mass balance). Hence, studies based on individual components of the Earth System have limited capacity to represent all relevant processes. This session aims to provide a platform for sharing coupled modelling experiences incorporating the cryosphere in the polar regions.
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Facilitating remote sensing applications across the terrestrial Arctic
We solicit both technical and scientific contributions from modelling studies in which feedback and emergent properties between the cryosphere and other Earth System components in polar regions are investigated, better understood, and possibly even quantified. In addition to application of coupled modelling to real world domains, contributions are also invited from idealised studies and intercomparisons, such as the Marine Ice Sheet – Ocean Intercomparison Project (MISOMIP).
Environmental changes in terrestrial ecosystems and coastal areas across the Arctic can only be fully addressed by using remote sensing observations and modelling. However, due to the multiscale complexity of the landscape, to limitations related to illumination and atmospheric conditions, bridging the gap between field and satellite observations remains a major challenge. Contributions may include recent advances in instrumentation and methodology for validation and calibration of remote sensing products, applications of joint use of in situ and satellite records to tackle science questions, demonstrate the utility of UAV for bridging the scale gap, progress for standardization (protocols) or reviewing challenges.
We specifically welcome contributions within the framework of T-MOSAiC aiming to coordinate activities that will both aid and benefit from MOSAiC (especially the modelling components) by extending the work to the lands surrounding the Arctic Ocean and to the northern communities.
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Public information:
We divide our session time slot into 4 parts:
(5min Introduction)
15:35 - 16:04 Presentations of "Coupled modelling in polar regions" (5min invited talk by Xylar Asay-Davis followed by 2min pitch talks of all authors)
16:04 - 16:16 2min vPICO talks of "Facilitating remote sensing applications across the terrestrial Arctic"
--- from 16:16 on individual text chat discussion with each author are possible in parallel windows ---
16:16 - 16:45 Discussion and open questions: Coupled modelling in the polar regions
16:45 - 17:00 Discussion on the status of T-MOSAIC: The final discussion for the remote sensing section will allow for additional questions (left open after the individual chats) and will specifically focus on the status of T-MOSAIC.
Co-organized by AS5/OS1
Convener: Konstanze HaubnerECSECS | Co-conveners: Annett Bartsch, Rupert Gladstone, Jeffrey KerbyECSECS, Yoshihiro Nakayama, Shuting Yang, Gonçalo Vieira
vPICO presentations
| Wed, 28 Apr, 15:30–17:00 (CEST)
Public information:
We divide our session time slot into 4 parts:
(5min Introduction)
15:35 - 16:04 Presentations of "Coupled modelling in polar regions" (5min invited talk by Xylar Asay-Davis followed by 2min pitch talks of all authors)
16:04 - 16:16 2min vPICO talks of "Facilitating remote sensing applications across the terrestrial Arctic"
--- from 16:16 on individual text chat discussion with each author are possible in parallel windows ---
16:16 - 16:45 Discussion and open questions: Coupled modelling in the polar regions
16:45 - 17:00 Discussion on the status of T-MOSAIC: The final discussion for the remote sensing section will allow for additional questions (left open after the individual chats) and will specifically focus on the status of T-MOSAIC.

vPICO presentations: Wed, 28 Apr

Chairpersons: Jeffrey Kerby, Konstanze Haubner, Shuting Yang
15:30–15:35
Coupled modelling in the polar regions
15:35–15:40
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EGU21-11918
|
solicited
Xylar Asay-Davis, Christopher Y. S. Bull, Stephen Cornford, Eva Cougnon, Jan De Rydt, Benjamin K. Galton-Fenzi, Rupert Gladstone, Daniel Goldberg, David Gwyther, James Jordan, Nicolas Jourdain, Gunter Leguy, William Lipscomb, Gustavo Marques, Daniel F. Martin, Yoshihiro Nakayama, Kaitlin A. Naughten, Robin S. Smith, Hélène Seroussi, and Chen Zhao

The Marine Ice Sheet-Ocean Model Intercomparison Project (MISOMIP) is a community effort sponsored by the Climate and Cryosphere (CliC) project.  MISOMIP aims to design and coordinate a series of MIPs—some idealized and realistic—for model evaluation, verification with observations, and future projections for key regions of the West Antarctic Ice Sheet (WAIS).  The first phase of the project, MISOMIP1, was an idealized, coupled set of experiments that combined elements from the MISMIP+ and ISOMIP+ standalone experiments for ice-sheet and ocean models, respectively.  These MIPs had 3 main goals: 1) to provide simplified experiments that allow model developers to compare their results with those from other models; 2) to suggest a path for testing components in the process of developing a coupled ice sheet-ocean model; and 3) to enable a large variety of parameter and process studies that branch off from these basic experiments.

Here, we describe preliminary analysis of the MISOMIP1 results.  Eight models in 14 configurations participated in the MIP.   In keeping with analysis of the MISMIP+ experiment, we find that the choice of basal friction parameterizations in the ice-sheet component (Weertman vs. Coulomb limited) has a particularly significant impact on the rate of ice-sheet retreat but the choice of stress approximation (SSA, SSA* or L1Lx) seems to have little impact.  Models with Coulomb-limited basal friction also tend to be those with the highest melt rates, confirming a positive feedback between melt and retreat in the MISOMIP1 configuration seen in previous work.  The ocean component’s treatment of the boundary layer below the ice shelf also has a significant impact on melt rates and resulting retreat, consistent with findings based on ISOMIP+.  Feedbacks between the components lead to localized features in the melt rates and the ice geometry not seen in standalone simulations, though the ~2-km horizontal and ~20-m vertical resolution of these simulations appears to be too coarse to produce long-lived, sub-ice-shelf channels seen at higher resolution.

How to cite: Asay-Davis, X., Bull, C. Y. S., Cornford, S., Cougnon, E., De Rydt, J., Galton-Fenzi, B. K., Gladstone, R., Goldberg, D., Gwyther, D., Jordan, J., Jourdain, N., Leguy, G., Lipscomb, W., Marques, G., Martin, D. F., Nakayama, Y., Naughten, K. A., Smith, R. S., Seroussi, H., and Zhao, C.: Analysis of the Marine Ice Sheet-Ocean Model Intercomparison Project first phase (MISOMIP1), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11918, https://doi.org/10.5194/egusphere-egu21-11918, 2021.

15:40–15:42
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EGU21-9977
Robin Smith, Pierre Mathiot, Antony Siahaan, Victoria Lee, Stephen Cornford, Jonathan Gregory, Antony Payne, Adrian Jenkins, Paul Holland, and Colin Jones

In this presentation we describe how models of the Greenland and Antarctic ice sheets have been incorporated in the global U.K. Earth System model (UKESM1) with a two-way coupling that passes fluxes of energy, water and the locations of ice surfaces between the component models. Offline, file-based coupling is used throughout to pass information between the components, which is both physically appropriate and convenient within the UKESM1 structure. Ice sheet surface mass balance is computed in the land surface model using sub-gridscale multi-layer snowpacks. Icebergs calved from the ice sheets are fed into a Langrangian iceberg drift scheme in the ocean. Ice shelf basal melt is explicitly calculated in cavities resolved by the ocean model, and ice sheet and shelf geometries are kept consistent in all components. We demonstrate that our coupled model remains stable when simulating changes in ice sheet height, extent and grounding-line position of hundreds of kilometres.

How to cite: Smith, R., Mathiot, P., Siahaan, A., Lee, V., Cornford, S., Gregory, J., Payne, A., Jenkins, A., Holland, P., and Jones, C.: Coupling the U.K. Earth System Model to dynamic models of the Greenland and Antarctic ice sheets, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9977, https://doi.org/10.5194/egusphere-egu21-9977, 2021.

15:42–15:44
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EGU21-12533
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ECS
Chris Barrell, Ian Renfrew, Steven Abel, Andrew Elvidge, and John King

During a cold-air outbreak (CAO) a cold polar airmass flows from the frozen land or ice surface, over the marginal ice zone (MIZ), then out over the comparatively warm open ocean. This constitutes a dramatic change in surface temperature, roughness and moisture availability, typically causing rapid change in the atmospheric boundary layer. Consequently, CAOs are associated with a range of severe mesoscale weather phenomena and accurate forecasting is crucial. Over the Nordic Seas CAOs also play a vital role in global ocean circulation, causing densification and sinking of ocean waters that form the headwaters of the Atlantic meridional overturning circulation. 

To tackle the lack of observations during wintertime CAOs and improve scientific understanding in this important region, the Iceland Greenland Seas Project (IGP) undertook an extensive field campaign during February and March 2018. Aiming to characterise the atmospheric forcing and the ocean response, particularly in and around the MIZ, the IGP made coordinated ocean-atmosphere measurements, involving a research vessel, a research aircraft, a meteorological buoy, moorings, sea gliders and floats.  

The work presented here employs these novel observational data to evaluate output from the UK Met Office global operational forecasting system and from a pre-operational coupled ocean-ice-atmosphere system. The Met Office aim to transition to a coupled operational forecast in the coming years, thus verification of model versions in development is essential. Results show that this coupled model’s sea ice is generally more accurate than a persistent field. However, it can also suffer from cold-biased sea surface temperatures around the MIZ, which influences the modelled near-surface meteorology. Both these effects demonstrate the crucial importance of accurate sea ice simulation in coupled model forecasting in the high latitudes. Hence, an ice edge metric is then used to quantify the accuracy of the coupled model MIZ edge at two ocean grid resolutions. 

How to cite: Barrell, C., Renfrew, I., Abel, S., Elvidge, A., and King, J.: Evaluating Met Office uncoupled and coupled forecasts during the Iceland Greenland Seas Project field campaign in 2018, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12533, https://doi.org/10.5194/egusphere-egu21-12533, 2021.

15:44–15:46
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EGU21-14017
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ECS
Adam Schneider, Stephen Price, Jonathan Wolfe, and Charles Zender

Since 1993, nearly 10 percent of the observed rise in global mean sea level can be attributed to the coincident increase in surface mass loss from the Greenland Ice Sheet (GrIS) (Meredith et al., 2019; WCRP, 2018). To determine the GrIS surface mass balance (SMB), defined as the ice sheet’s annual net (surface) mass increase due to snow accumulation minus ablation, a climate model can be coupled to a snowpack model, which enables simulating relevant hydrologic processes including precipitation, phase changes, and runoff. Recent developments within the Energy Exascale Earth System Model (E3SM) include an active ice sheet component. To explore GrIS snowpack conditions relevant to present-day climate, we conduct simulations demonstrating the evolution of SMB and accumulation of snowpack depth, first in E3SM’s land component (ELM). After forcing ELM’s surface condition using 20th century atmospheric reanalysis, we couple ELM to E3SM’s atmosphere component (EAM) and simulate both atmospheric and snowpack conditions over a fixed GrIS geometry. Finally, we activate the MPAS-Albany Land Ice model (MALI), which enables prognostic SMB calculations including elevation-change feedbacks. We find broad agreement in the spatial patterns of GrIS SMB compared to regional climate model (RACMO) and Community Earth System Model (CESM) simulations. We provide insights regarding the use of a statistical downscaling method, which involves using multiple elevation classes with time-varying areal coverages within ELM grid-cells. Within this dynamic system, we can begin investigating elevation feedbacks, where the atmospheric temperature lapse rate allows the SMB to accelerate both positively and negatively in a rapidly changing climate.

References

  • Meredith, M., M. Sommerkorn, S. Cassotta, C. Derksen, A. Ekaykin, A. Hollowed, G. Kofinas, A. Mackintosh, J. Melbourne-Thomas, M.M.C. Muelbert, G. Ottersen, H. Pritchard, and E.A.G. Schuur, 2019: Polar Regions. In: IPCC Special Report on the Ocean and Cryosphere in a Changing Climate [H.-O. Pörtner, D.C. Roberts, V. Masson-Delmotte, P. Zhai, M. Tignor, E. Poloczanska, K. Mintenbeck, A. Alegría, M. Nicolai, A. Okem, J. Petzold, B. Rama, N.M. Weyer (eds.)]. In press.
  • WCRP Global Sea Level Budget Group: Global sea-level budget 1993–present, Earth Syst. Sci. Data, 10, 1551–1590, https://doi.org/10.5194/essd-10-1551-2018, 2018.

How to cite: Schneider, A., Price, S., Wolfe, J., and Zender, C.: Surface Mass Balance of the Greenland Ice Sheet in the Energy Exascale Earth System Model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14017, https://doi.org/10.5194/egusphere-egu21-14017, 2021.

15:46–15:48
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EGU21-13457
Darin Comeau, Xylar Asay-Davis, Carolyn Begeman, Matthew Hoffman, Wuyin Lin, Mark Petersen, Stephen Price, Andrew Roberts, Luke Van Roekel, Milena Veneziani, Jonathan Wolfe, and Adrian Turner

The processes responsible for freshwater flux from the Antarctic Ice Sheet (AIS) -- ice-shelf basal melting and iceberg calving -- are generally poorly represented in current Earth System Models (ESMs). Here, we document the first effort to date at simulating the ocean circulation and exchanges of heat and freshwater within ice-shelf cavities in a coupled ESM, the Department of Energy's Energy Exascale Earth System Model (E3SM). As a step towards full ice-sheet coupling, we implemented static Antarctic ice-shelf cavities and the ability to calculate ice-shelf basal melt rates from the heat and freshwater fluxes computed by the ocean model. In addition, we added the capability to prescribe forcing from iceberg melt, allowing us to realistically represent the other dominant mass loss process from the AIS. In global, low resolution (i.e., non-eddying ocean) simulations, we find high sensitivity of modeled ocean/ice shelf interactions to the ocean state, which can result in a tipping point to high melt regimes under certain ice shelves, presenting a significant challenge to representing the ocean/ice shelf system in a coupled ESM. We show that inclusion of a spatially dependent parameterization of eddy-induced transport reduces biases in water mass properties on the Antarctic continental shelf. With these improvements, E3SM produces realistic and stable ice-shelf basal melt rates across the continent under pre-industrial climate forcing. We also show preliminary results using an ocean/sea-ice grid that makes use of E3SM’s regional-refinement capability, where increased resolution (down to 12km) is placed in the Southern Ocean around Antarctica, bypassing the need for parameterization of eddy-induced transport in this region. The accurate representation of these processes within a coupled ESM is an important step towards reducing uncertainties in projections of the Antarctic response to climate change and Antarctica's contribution to global sea-level rise.

How to cite: Comeau, D., Asay-Davis, X., Begeman, C., Hoffman, M., Lin, W., Petersen, M., Price, S., Roberts, A., Van Roekel, L., Veneziani, M., Wolfe, J., and Turner, A.: Ice-shelf Basal Melt Rates in the Energy Exascale Earth System Model (E3SM), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13457, https://doi.org/10.5194/egusphere-egu21-13457, 2021.

15:48–15:50
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EGU21-8317
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ECS
Francois Massonnet, Sara Fleury, Florent Garnier, Ed Blockley, Pablo Ortega Montilla, Juan C. Acosta Navarro, Leandro Ponsoni, and François Klein

It is well established that winter and spring Arctic sea-ice thickness anomalies are a key source of predictability for late summer sea-ice concentration. While numerical general circulation models (GCMs) are increasingly used to perform seasonal predictions, they are not systematically taking advantage of the wealth of polar observations available. Data assimilation, the study of how to constrain GCMs to produce a physically consistent state given observations and their uncertainties, remains, therefore, an active area of research in the field of seasonal prediction. With the recent advent of satellite laser and radar altimetry, large-scale estimates of sea-ice thickness have become available for data assimilation in GCMs. However, the sea-ice thickness is never directly observed by altimeters, but rather deduced from the measured sea-ice freeboard (the height of the emerged part of the sea ice floe) based on several assumptions like the depth of snow on sea ice and its density, which are both often poorly estimated. Thus, observed sea-ice thickness estimates are potentially less reliable than sea-ice freeboard estimates. Here, using the EC-Earth3 coupled forecasting system and an ensemble Kalman filter, we perform a set of sensitivity tests to answer the following questions: (1) Does the assimilation of late spring observed sea-ice freeboard or thickness information yield more skilful predictions than no assimilation at all? (2) Should the sea-ice freeboard assimilation be preferred over sea-ice thickness assimilation? (3) Does the assimilation of observed sea-ice concentration provide further constraints on the prediction? We address these questions in the context of a realistic test case, the prediction of 2012 summer conditions, which led to the all-time record low in Arctic sea-ice extent. We finally formulate a set of recommendations for practitioners and future users of sea ice observations in the context of seasonal prediction.

How to cite: Massonnet, F., Fleury, S., Garnier, F., Blockley, E., Ortega Montilla, P., Acosta Navarro, J. C., Ponsoni, L., and Klein, F.: Sea-ice freeboard or thickness? Design choices in the context of data assimilation in the coupled numerical prediction system EC-Earth3 for seasonal Arctic sea ice prediction, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8317, https://doi.org/10.5194/egusphere-egu21-8317, 2021.

15:50–15:52
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EGU21-15716
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ECS
Effect of Southern Ocean freshwater export on the AMOC using an earth system model with interactive icebergs 
(withdrawn)
Lars Ackermann, Thomas Rackow, Paul Gierz, Gregor Knorr, and Gerrit Lohmann
15:52–15:54
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EGU21-799
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ECS
Catherine Drinkorn, Jan Saynisch-Wagner, Gabriele Uenzelmann-Neben, and Maik Thomas

Ocean sediment drifts contain important information about past bottom currents but a direct link from the study of sedimentary archives to ocean dynamics is not always possible. To close this gap for the North Atlantic, we set up a  new coupled Ice-Ocean-Sediment Model of the entire Pan-Arctic region. In order to evaluate the potential dynamics of the model, we conducted decadal sensitivity experiments. In our model contouritic sedimentation shows a significant sensitivity towards climate variability for most of the contourite drift locations in the model domain. We observe a general decrease of sedimentation rates during warm conditions with decreasing atmospheric and oceanic gradients and an extensive increase of sedimentation rates during cold conditions with respective increased gradients. We can relate these results to changes in the dominant bottom circulation supplying deep water masses to the contourite sites under different climate conditions. A better understanding of northern deep water pathways in the Atlantic Meridional Overturning Circulation (AMOC) is crucial for evaluating possible consequences of climate change in the ocean.

How to cite: Drinkorn, C., Saynisch-Wagner, J., Uenzelmann-Neben, G., and Thomas, M.: Decadal climate sensitivity of contouritic sedimentation in a dynamically coupled ice-ocean-sediment model of the Pan-Arctic region, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-799, https://doi.org/10.5194/egusphere-egu21-799, 2021.

15:54–15:56
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EGU21-10448
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ECS
Chen Zhao, Rupert Gladstone, Ben Galton-Fenzi, and David Gwyther

The ocean-driven basal melting has important implications for the stability of ice shelves in Antarctic, which largely affects the ice sheet mass balance, ocean circulation, and subsequently global sea level rise. Due to the limited observations in the ice shelf cavities, the couple ice sheet ocean models have been playing a critical role in examining the processes governing basal melting. In this study we use the Framework for Ice Sheet-Ocean Coupling (FISOC) to couple the Elmer/Ice full-stokes ice sheet model and the Regional Ocean Modeling System (ROMS) ocean model to model ice shelf/ocean interactions for an idealised three-dimensional domain. Experiments followed the coupled ice sheet–ocean experiments under the first phase of the Marine Ice Sheet–Ocean Model Intercomparison Project (MISOMIP1). A periodic pattern in the simulated mean basal melting rates is found to be highly consistent with the maximum barotropic stream function and also the grounding line retreat row by row,  which is likely to be related with the gyre break down near the grounding line caused by some non-physical instability events from the ocean bottom. Sensitivity tests are carried out, showing that this periodic pattern is not sensitive to the choice of couple time intervals and horizontal eddy viscosities but sensitive to vertical resolution in the ocean model, the chosen critical water column thickness in the wet-dry scheme, and the tracer properties for the nudging dry cells at the ice-ocean interface boundary. Further simulations are necessary to better explain the mechanism involved in the couple ice-ocean system, which is very significant for its application on the realistic ice-ocean systems in polar regions.

How to cite: Zhao, C., Gladstone, R., Galton-Fenzi, B., and Gwyther, D.: Representation of basal melting in idealised coupled ice sheet ocean models, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10448, https://doi.org/10.5194/egusphere-egu21-10448, 2021.

15:56–15:58
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EGU21-6063
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ECS
Moritz Kreuzer, Ronja Reese, Willem Huiskamp, Stefan Petri, Torsten Albrecht, Georg Feulner, and Ricarda Winkelmann

The past and future evolution of the Antarctic Ice Sheet is largely controlled by interactions between the ocean and floating ice shelves. To investigate these interactions, coupled ocean and ice sheet model configurations are required. Previous modelling studies have mostly relied on high resolution configurations, limiting these studies to individual glaciers or regions over short time scales of decades to a few centuries. To study global and long term interactions, we developed a framework to couple the dynamic ice sheet model PISM with the global ocean general circulation model MOM5 via the ice-shelf cavity module PICO. Since ice-shelf cavities are not resolved by MOM5, but parameterized with the box model PICO, the framework allows the ice sheet and ocean model to be run at resolution of 16 km and 3 degrees, respectively. We present first results from our coupled setup and discuss stability, feedbacks, and interactions of the Antarctic Ice Sheet and the global ocean system on millennial time scales.

How to cite: Kreuzer, M., Reese, R., Huiskamp, W., Petri, S., Albrecht, T., Feulner, G., and Winkelmann, R.: First results from coupling the Parallel Ice Sheet Model with the Modular Ocean Model via an Antarctic ice-shelf cavity module, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6063, https://doi.org/10.5194/egusphere-egu21-6063, 2021.

15:58–16:00
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EGU21-4325
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ECS
Charles Pelletier, Lars Zipf, Konstanze Haubner, Deborah Verfaillie, Hugues Goosse, Frank Pattyn, Pierre Mathiot, and Thierry Fichefet

From at least 1979 up until 2016, the surface of the Southern Ocean cooled down, leading to a small Antarctic sea ice extent increase, which is in stark contrast with the Arctic Ocean. The attribution of the origin of these robust observations is still very uncertain. Among other phenomena, the direct, two-way interactions between the Southern Ocean and the Antarctic ice sheet, through basal melting of its numerous and large ice-shelf cavities, have been suggested as a potentially important contributor of this cooling. In order to address this question, we perform multidecadal coupled ice sheet – ocean numerical simulations relying on f.ETISh-v1.7 and NEMO3.6-LIM3 for simulating the Antarctic ice sheet and Southern Ocean (including sea ice), respectively. This presentation is twofold. First, we present the technical aspects of the coupling infrastructure (e.g. workflow and exchanged information in between models). Second, we investigate the ice sheet – ocean feedbacks on the Southern Ocean, their interactions, and the roles of the related physical mechanisms on the ocean surface cooling.

How to cite: Pelletier, C., Zipf, L., Haubner, K., Verfaillie, D., Goosse, H., Pattyn, F., Mathiot, P., and Fichefet, T.: Impact of ice sheet – ocean interactions on the Southern Ocean using fully coupled models over a circumpolar domain, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4325, https://doi.org/10.5194/egusphere-egu21-4325, 2021.

16:00–16:02
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EGU21-12417
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ECS
Lars Zipf, Charles Pelletier, Konstanze Haubner, Sainan Sun, and Frank Pattyn

Sub-shelf melting is the main driver of Antarctica's ice sheet mass loss. However, sub-shelf melt rate parameterizations for standalone ice models lack the capability to capture complex ocean circulation within ice shelf cavities. To overcome drawbacks of standalone models and to improve melt parameterizations, high resolution coupling of ice sheet and ocean models are capable of hindcasting past decennia and be compared to observations.

Here, we present first results of a hindcast (1985-2018) of the new circumpolar coupled Southern Ocean – Antarctic ice sheet configuration, developed within the framework of the PARAMOUR project. The configuration is based on the ocean and sea ice model NEMO3.6-LIM3 and the ice sheet model f.ETISh v1.7. The coupling routine facilitates exchange of monthly sub-shelf melt rates (from ocean to ice model) and evolving ice shelf cavity geometry (from ice to ocean model).

We investigate the impact of the coupling frequency (more precisely, the frequency of updating the ice shelf cavity geometry within the ocean model) on the sub-shelf melt rates and its feedback on the ice dynamics. We further compare the sub-shelf melt rates of the coupled setup to those of the standalone ice sheet model with different sub-shelf melt rate parametrizations (ISMIP6, plume, PICO, PICOP) and investigate the sensitivity of the response of the ice sheet for the different basal melt rate patterns on decadal time scales.

How to cite: Zipf, L., Pelletier, C., Haubner, K., Sun, S., and Pattyn, F.: Ice sheet response to sub-shelf melt rates in coupled and uncoupled peri-Antarctic ice-sheet model simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12417, https://doi.org/10.5194/egusphere-egu21-12417, 2021.

16:02–16:04
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EGU21-13707
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ECS
Ice-mass changes in Aurora basin, East Antarctica, in coupled and uncoupled ice-ocean simulations
(withdrawn)
Konstanze Haubner, Guillian Van Achter, Charles Pelletier, Lars Zipf, Thierry Fichefet, Hugues Goosse, and Frank Pattyn
Facilitating remote sensing applications across the terrestrial Arctic
16:04–16:06
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EGU21-985
Simon Zwieback and Franz Meyer

Despite the critical role of ground ice for permafrost ecosystems and terrain stability, we lack fine-scale ground ice maps across almost the entire Arctic. This is chiefly because ground ice cannot be observed directly from space. Here, we analyse late-season subsidence from Sentinel-1 InSAR satellite observations as a physically based indicator of vulnerable excess ground ice at the top of permafrost. The key idea is that the thaw front can penetrate materials that were previously perennially frozen at the end of a warm summer, triggering subsidence where the permafrost is ice rich. We assess the idea by comparing the InSAR observations to permafrost cores and an independently derived ground ice classification. 

We find that the late-season subsidence in an exceptionally warm summer was 4 - 8 cm (5th - 95th percentile) in the ice-rich areas, while it was lower in ice-poor areas (-1 - 2 cm). The observed distributions for ice-rich and ice-poor terrain overlapped by only 2%, demonstrating high sensitivity and specificity for identifying top-of-permafrost excess ground ice. 

The strengths of late-season subsidence include the ease of automation and its applicability to areas that lack conspicuous manifestations of ground ice, as often occurs on hillslopes. The biggest limitation is that it is not sensitive to excess ground ice below the thaw front and thus the total ice content. A further challenge is the sub-resolution variability in ground ice, ice-wedge polygons being a striking example, which needs to be accounted for when interpreting and validating the results.

We expect late-season subsidence to enhance the automated mapping of ice-rich permafrost terrain, complementing existing (predominantly non-automated) approaches based on largely indirect associations of ice content with vegetation and periglacial landforms. The suitability of satellite-observed late-season subsidence for mapping ice-rich permafrost can contribute to anticipating terrain instability in the Arctic and sustainably stewarding its ecosystems.

How to cite: Zwieback, S. and Meyer, F.: Identifying ice-rich permafrost using remotely sensed late-season subsidence, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-985, https://doi.org/10.5194/egusphere-egu21-985, 2021.

16:06–16:08
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EGU21-15632
Carla Mora, Gonçalo Vieira, Pedro Pina, Dustin Whalen, and Annett Bartsch

Arctic permafrost coasts represent about 34% of the Earth’s coastline, with long sections affected by high erosion rates, increasingly threatening coastal communities. Year-round reduction in Arctic sea ice is forecasted and by the end of the 21st century, models indicate a decrease in sea ice area from 43 to 94% in September and from 8 to 34% in February (IPCC, 2014). An increase of the ice-free season leads to a longer exposure to wave action. Monitoring the Arctic coasts is limited by remoteness, climate harshness and difficulty of access for direct surveying, but also, when using satellite remote sensing, by frequent high cloudiness conditions and by illumination. In order to overcome these limitations, three sites at the Beaufort Sea Coast (Clarence lagoon, Hopper Island and Qikiqtaruk/Herschel Island) have been selected for monitoring using very high-resolution microwave X-band spotlight PAZ imagery from Hisdesat. Bluff top, thaw-slump headwalls and water lines were digitised from images acquired during the ice-free seasons of 2019 and 2020 at sub-monthly time-steps. The effects of coastal exposure on delineation accuracy in relation to satellite overpass geometry have been assessed and coastal changes have been quantified and compared to meteorological and tide-gauge data. The results show that PAZ imagery allow for monitoring and quantifying coastal changes at sub-monthly intervals and following the evolution of coastal features, such as small mud-flow fans and retrogressive thaw slumps. This shows that high resolution microwave imagery has a strong potential for significantly advancing coastal monitoring in remote Arctic areas. This research is part of project Nunataryuk funded under the European Union's Horizon 2020 Research and Innovation Programme (grant agreement no. 773421) and of Hisdesat project Coastal Monitoring for Permafrost Research in the Beaufort Sea Coast (Canada). 

How to cite: Mora, C., Vieira, G., Pina, P., Whalen, D., and Bartsch, A.: Evaluation of PAZ satellite imagery for the assessment of intra-seasonal dynamics of permafrost coasts (Beaufort Sea, Canada), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15632, https://doi.org/10.5194/egusphere-egu21-15632, 2021.

16:08–16:10
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EGU21-15405
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ECS
Pedro Freitas, Gonçalo Vieira, Carla Mora, João Canário, Diogo Folhas, and Warwick F. Vincent

Warming of the circumpolar north is accelerating permafrost thaw, with implications for landscapes, hydrology, ecosystems and the global carbon cycle. In subarctic Canada, abrupt permafrost thaw is creating widespread thermokarst lakes. Little attention has been given to small waterbodies with area less than 10,000 m2, yet these are biogeochemically more active than larger lakes. Additionally, the landscapes where they develop show intense shrubification and terrestrialization processes, with increases in area and height of shrub and tree communities. Tall vegetation that is colonizing waterbody margins can cast shadows that impact productivity, thermal regime and the water spectral signal, which in satellite data generates pixels with mixed signatures between sunlit and shaded surfaces. We undertook UAV surveys using optical and multispectral sensors at long-term monitoring sites of the Center for Northern Studies (CEN) in subarctic Canada, from the sporadic (SAS/KWAK) to the discontinuous (BGR) permafrost zones in the boreal forest-tundra transition zone. This ultra-high spatial resolution data enabled spectral characterization and 3D reconstruction of the study areas. Ultra-high resolution digital surface models were produced to model shadowing at satellite overpass time (WorldView, PlanetScope and Sentinel-2). We then analyzed the impacts of surrounding vegetation and cast shadows on lake surface spectral reflectance derived from satellite imagery. Ultra-high resolution UAV data allows generating accurate shadow models and can be used to improve the assessment of errors and accuracy of satellite data analysis. Particularly, we identify different spectral signal impacts of cast shadows according to lake color, which highlight the need for special attention of this issue onto lakes with more turbidity.

This research is funded by the Portuguese Foundation for Science and Technology (FCT) under the project THAWPOND (PROPOLAR), by the Centre of Geographical Studies (FCT I.P. UIDB/00295/2020 and UIDP/00295/2020), with additional support from ArcticNet (NCE), Sentinel North (CFREF) and CEN and is a contribution to T-MOSAiC. PF is funded by FCT (SFRH/BD/145278/2019).

How to cite: Freitas, P., Vieira, G., Mora, C., Canário, J., Folhas, D., and Vincent, W. F.: Ultra-high resolution assessment of potential impacts of vegetation shadows on satellite-derived spectral signals from small thermokarst lakes in the boreal forest-tundra transition zone (subarctic Canada), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15405, https://doi.org/10.5194/egusphere-egu21-15405, 2021.

16:10–16:12
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EGU21-13497
Birgit Heim, Iuliia Shevtsova, Stefan Kruse, Ulrike Herzschuh, Agata Buchwal, Grzegorz Rachlewicz, and Annett Bartsch

Vegetation biomass is a globally important climate-relevant terrestrial carbon pool. Landsat, Sentinel-2 and Sentinel-1 satellite missions provide a landscape-level opportunity to upscale tundra vegetation communities and biomass in high latitude terrestrial environments. We assessed the applicability of landscape-level remote sensing for the low Arctic Lena Delta region in Northern Yakutia, Siberia, Russia. The Lena Delta is the largest delta in the Arctic and is located North of the treeline and the 10 °C July isotherm at 72° Northern Latitude in the Laptev Sea region. We evaluated circum-Arctic harmonized ESA GlobPermafrost land cover and vegetation height remote sensing products covering subarctic to Arctic land cover types for the central Lena Delta. The products are freely available and published in the PANGAEA data repository under https://doi.org/10.1594/PANGAEA.897916, and https://doi.org/10.1594/PANGAEA.897045.

Vegetation and biomass field data (30 m x 30 m plot size) and shrub samples for dendrology were collected during a Russian-German expedition in summer 2018 in the central Lena Delta. We also produced a regionally optimized land cover classification for the central Lena Delta based on the in-situ vegetation data and a summer 2018 Sentinel-2 acquisition that we optimized on the biomass and wetness regimes. We also produced biomass maps derived from Sentinel-2 at a pixel size of 20 m investigating several techniques. The final biomass product for the central Lena Delta shows realistic spatial patterns of biomass distribution, and also showing smaller scale patterns. However, patches of high shrubs in the tundra landscape could not spatially be resolved by all of the landscape-level land cover and biomass remote sensing products.

Biomass is providing the magnitude of the carbon flux, whereas stand age is irreplaceable to provide the cycle rate. We found that high disturbance regimes such as floodplains, valleys, and other areas of thermo-erosion are linked to high and rapid above ground carbon fluxes compared to low disturbance on Yedoma upland tundra and Holocene terraces with decades slower and in magnitude smaller above ground carbon fluxes.

How to cite: Heim, B., Shevtsova, I., Kruse, S., Herzschuh, U., Buchwal, A., Rachlewicz, G., and Bartsch, A.: Landscape-level remote sensing for upscaling of land cover, above ground biomass and above ground carbon fluxes in the Lena River Delta (Northern Yakutia, Russia), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13497, https://doi.org/10.5194/egusphere-egu21-13497, 2021.

16:12–16:14
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EGU21-10296
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ECS
Helena Bergstedt, Benjamin Jones, Donald Walker, Jana Pierce, Annett Bartsch, and Georg Pointner

Increased industrial development in the Arctic has led to a rapid expansion of infrastructure in the region. Past research shows that infrastructure in the form of roads, pipelines and various building types impacts the surrounding landscape directly and indirectly by changing vegetation patterns, locally increasing ground temperatures, changing the local hydrology, introducing road dust into the natural environment, and affecting the distribution and timing of seasonal snow cover. Localized impacts of infrastructure on snow distribution and snow melt timing and duration feedbacks into the coupled Arctic system causing a series of cascading effects that remain poorly understood.  In this study, we quantify spatial and temporal patterns of snow-off dates in the Prudhoe Bay Oilfields (PBO), North Slope, Alaska using multispectral remote sensing data from the Sentinel-2 constellation. The Sentinel-2 satellite constellation provides good spatial and temporal coverage of Arctic regions with adequate spatial resolution to quantify and monitor infrastructure impacts on the natural environment in polar regions. We derive the Normalized Difference Snow Index (NDSI) to quantify the presences and absences of snow on a pixel-by-pixel basis between 2015 and 2020. Additional indices, like the Normalized Difference Vegetation Index (NDVI) and the Normalized Difference Water Index (NDWI) were derived to understand linkages between patterns in vegetation and surface hydrology, respectively, to patterns in snow-off dates that are influenced by the presence and type of infrastructure on a regional basis at PBO. Newly available infrastructure data sets derived from Sentinel-1 and 2 data were employed to quantify differences in snow melt patterns in relation to distance to roads and other types of infrastructure. Near-surface ground temperature measurements from multiple transects oriented in a perpendicular direction from the road up to 100 m provided ground-truth observations for snow-off timing derived from the remote sensing analysis. Our results from the regional remote sensing analysis show a relationship between snow-off date and distance to different types of infrastructure that vary by their use and traffic load during the snowmelt period as well as their orientation relative to the prevailing wind direction. Results from field data observations indicate that the early onset of snowmelt near heavily traveled infrastructure corridors impacts near-surface soil freezing degree days, vegetation productivity, and waterbody surface cover.

How to cite: Bergstedt, H., Jones, B., Walker, D., Pierce, J., Bartsch, A., and Pointner, G.: Quantifying the spatial and temporal influence of infrastructure on seasonal snow melt timing and its influence on vegetation productivity and early season surface water cover in the Prudhoe Bay Oilfields, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10296, https://doi.org/10.5194/egusphere-egu21-10296, 2021.

16:14–16:16
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EGU21-15639
Annett Bartsch

Rain-on-snow modifies snow properties and can lead to the formation of ice crusts which impact wildlife and also vegetation. Events in the Arctic have been recently linked to specific sea ice conditions (longer open water season) for Siberia. Specifically microwave satellite data have been shown applicable for identification of such events across the Arctic. Related snow structure changes can be observed specifically over Scandinavia, northern European Russia and Western Siberia as well as Alaska (Bartsch, 2010). Events which had severe impacts for reindeer herder herding have occurred several times in the last two decades.

Challenges further include the categorization of severity of events and attribution of observations to rain-on-snow events.

Calibration and validation of detection schemes have been largely based on indirect measures. Usually a combination of air temperature and snow height measurements, supported by reports of such events are analysed.

In this presentation, the utility of current calibration and validation approaches are discussed. Requirements towards in situ data from the viewpoint of satellite based retrievals are outlined.

Bartsch, A. Ten Years of SeaWinds on QuikSCAT for Snow Applications. Remote Sens. 2010, 2, 1142-1156.

How to cite: Bartsch, A.: Facilitating rain-on-snow detection with satellite data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15639, https://doi.org/10.5194/egusphere-egu21-15639, 2021.

16:16–17:00