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Abstract
The temporal and spatial variability of sea-ice radar signatures in the Southern Ocean during late winter, spring and early summer from QuikSCAT data is presented. We observe a circumpolar and broad band of sea-ice close to the marginal ice zone that is characterized by very high radar backscatter. This feature is explained through detailed in situ observations of snow and sea-ice properties as well as in relation to meteorological conditions, which were derived from US National Center for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) reanalysis data. Our results indicate that high backscatter regions are caused by metamorphous snow, which forms through re-freezing after short-term melt events. This process is connected with the episodic passes of low-pressure systems entraining warmer air from the north. South of the Antarctic Circumpolar Trough, sea-ice is not affected by this influence and shows spatially homogenous microwave signatures with low backscatter.
Acknowledgements
The authors are very grateful to two anonymous reviewers for their helpful and constructive comments. Moreover, we would like to thank the members of the ISPOL and WWOS expeditions for encouraging discussions and lending a helping hand during fieldwork, especially Anja Nicolaus, Takenobu Toyota and Zhijun Li. Scatterometer data were provided by the French Research Institute for Exploitation of the Sea, sea-ice concentrations by the US National Snow and Ice Data Center and meteorological reanalysis data by NCEP/NCAR. This study was partly funded by the German Research Foundation (DFG) under contract BA 2060/2-2 and HA 2724/4-2.