CR7.2

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.