Remote sensing of sea ice: advances during the DAMOCLES project

• Published in: The Cryosphere
• Main Authors: G. Heygster, V. Alexandrov, G. Dybkjær, W. von Hoyningen-Huene, F. Girard-Ardhuin, I. L. Katsev, A. Kokhanovsky, T. Lavergne, A. V. Malinka, C. Melsheimer, L. Toudal Pedersen, A. S. Prikhach, R. Saldo, R. Tonboe, H. Wiebe, E. P. Zege
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2012
• Subjects: geo; envir; Arctic; Svalbard; Ross Ice Shelf; Damocles; albedo; Global warming; Ice Shelf; Sea ice; The Cryosphere
• Online Access: https://doi.org/10.5194/tc-6-1411-2012; http://www.the-cryosphere.net/6/1411/2012/tc-6-1411-2012.pdf; https://doaj.org/article/7b193e178b8a4232a64cac0a18af0bff

In the Arctic, global warming is particularly pronounced so that we need to monitor its development continuously. On the other hand, the vast and hostile conditions make in situ observation difficult, so that available satellite observations should be exploited in the best possible way to extract geophysical information. Here, we give a résumé of the sea ice remote sensing efforts of the European Union's (EU) project DAMOCLES (Developing Arctic Modeling and Observing Capabilities for Long-term Environmental Studies). In order to better understand the seasonal variation of the microwave emission of sea ice observed from space, the monthly variations of the microwave emissivity of first-year and multi-year sea ice have been derived for the frequencies of the microwave imagers like AMSR-E (Advanced Microwave Scanning Radiometer on EOS) and sounding frequencies of AMSU (Advanced Microwave Sounding Unit), and have been used to develop an optimal estimation method to retrieve sea ice and atmospheric parameters simultaneously. In addition, a sea ice microwave emissivity model has been used together with a thermodynamic model to establish relations between the emissivities from 6 GHz to 50 GHz. At the latter frequency, the emissivity is needed for assimilation into atmospheric circulation models, but is more difficult to observe directly. The size of the snow grains on top of the sea ice influences both its albedo and the microwave emission. A method to determine the effective size of the snow grains from observations in the visible range (MODIS) is developed and demonstrated in an application on the Ross ice shelf. The bidirectional reflectivity distribution function (BRDF) of snow, which is an essential input parameter to the retrieval, has been measured in situ on Svalbard during the DAMOCLES campaign, and a BRDF model assuming aspherical particles is developed. Sea ice drift and deformation is derived from satellite observations with the scatterometer ASCAT (62.5 km grid spacing), with visible AVHRR observations (20 ...