Day 4

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Paper title Impact of different retrieval methodologies and snow depths on altimetry-based estimations of pan-Arctic sea ice thickness, and sea ice outflow and freshwater fluxes through Fram Strait
  1. Renée Mie Fredensborg Hansen DTU Space Speaker
  2. Henriette Skourup DTU Space
  3. Roberto Saldo Technical University of Denmark
  4. Antoine Laforge SERCO c/o ESA-ESRIN
  5. Florent Garnier CNRS-LEGOS
  6. Ole Baltazar Andersen DTU Space
  7. Alessandro Di Bella SERCO c/o ESA-ESRIN
  8. Sara Fleury OMP/LEGOS
  9. Jack Landy UiT the Arctic University of Norway
  10. Pierre Féménias ESA/ESRIN
  11. Jérôme Bouffard ESA - European Space Agency
Form of presentation Poster
  • A9. Polar Science and Cryosphere
    • A9.04 Mass Balance of the Cryosphere
Abstract text In the climate system, heat is transferred between the poles and the equator through both atmospheric and oceanic circulation. One key component in transferring heat is through freshwater exchange in the Arctic, which is moderated by several elements, one of them being the outflow of freshwater from sea ice. To describe the heat transfer and possible temporal changes, it is vital to have accurate mapping of freshwater fluxes and their changes over time. Using earth observation data, volume of sea ice has been estimated using gridded sea ice thickness, sea ice concentration and ice drift velocity products, and through designated flux gates, the outflow of sea ice has been estimated. However, various sea ice thickness products exist with ranges of different methodologies and auxiliary products applied – all of this introduce differences in the estimated fluxes.

This study aims at estimating the impact that different retrieval methodologies and snow products have on the pan-Arctic sea ice thickness distribution and consequently, on the derived sea ice outflow, when using different gridded sea ice thickness product as input in the sea ice outflow computations. In this study, we utilise three different radar freeboard products derived from CryoSat-2 observations; the Threshold First Maximum Retracker Algorithm with a threshold of 50% (TFMRA50), Log-normal Altimeter Retracker Model (LARM), and Synthetic Aperture Radar (SAR) Altimetry MOde Studies and Applications over ocean (SAMOSA+). These are used to compute sea ice thickness estimates in combination with five different snow depth products: modified Warren 1999 (mW99), W99 fused with the Advanced Scanning Microwave Radiometer-2 (W99/AMSR2), SnowModel, NASA Eulerian Snow On Sea Ice Model (NESOSIM) and Altimetric Snow Depth (ASD), during the winter (Nov--Apr) of 2014--2015, resulting in 15 different sea ice thickness products for each month.

We compare the derived sea ice thickness products to investigate the differences that retrieval methodologies and snow depth products have on the sea ice distribution. Furthermore, we investigate the impact that these differences have on sea ice volume fluxes, which are further compared with outflow estimates from former studies. We also discuss how different sea ice drift estimates (based on either high-resolution SAR or passive-microwave low-resolution drift observations) and selection of fluxgate can impact the estimated volume fluxes. Finally, we derive the related freshwater fluxes and compare how the choice of the retrieval method and auxiliary data products affect the results.