Recent Antarctic Sea Ice Surface Melt from Satellite Remote Sensing (REASSESS)

• Applicant: Dr. Larysa Istomina
• Subject Area: Oceanography
• Term: since 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 424326801

In January 2017, a massive sea ice surface melt event occurred in the vicinity of the Japanese Syowa station in Antarctica. The field party of the icebreaker RV Shirase reported multiple melt ponds on top of landfast and free floating ice. Massive ponding has been observed in McMurdo Sound a year earlier, in January 2016.Melt ponds, puddles of melt water on top of the sea ice, are common in the Arctic during summer but are thought of as extremely rare in Antarctica. In the currently running project REASSESS we have shown with the aid of satellite data that the melt ponding observed in the vicinity of Syowa station not only in January 2017 but also in January 2018, 2019, 2020, and thus proved that some melt ponds have been simply overlooked before due to lack of in situ observations. We have for the first time presented global Antarctic melt pond fraction maps produced as daily average from all the satellite overflights of a given day, and located more potential melt ponding events also in other regions of the ice-covered Southern Ocean. These new data are being compiled into the first consistent, global Antarctic melt pond/blue ice dataset. Instead of qualitative estimates “Antarctic melt ponds are rare”, we are able to provide satellite-derived area fractions of the melt ponds and blue ice in the Southern Ocean for many years of satellite data.However, the in situ campaigns fitting to the specific conditions needed to validate our retrievals (sunlight, cloud free conditions) are rare, so that the validation and calibration of the developed retrievals comes short.In the proposed renewal project, we plan to carry out a dedicated aircraft campaign funded by AWI. One of its objectives will be to observe the melt ponds/blue ice on top of Antarctic landfast and freely floating pack ice. The outcome of this campaign will be a unique in situ dataset which will serve as validation and calibration for our remote sensing melt pond retrieval. In addition, we plan to employ satellite imagery of very high spatial resolution as one more source of validation data. These data will be acquired also as follow-up to the aircraft campaign and will potentially provide validation time series. The calibrated melt pond fraction retrieval will be used for a newly planned interdisciplinary comparison of melt pond dataset with the jellyfish in situ data under the Antarctic sea ice. Thus, we test a hypothesis that the under-ice ecosystem is affected by the sea ice conditions on the surface via the increased sea ice transmittance.The improved melt pond fraction trends which will be produced based on the above research will clarify how much did the Antarctic sea ice change in the recent 20 years of satellite observations.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 1158: Infrastructure area - Antarctic Research with Comparative Investigations in Arctic Sea Ice Areas
• International Connection: Japan
• Co-Investigators: Professor Dr. Christian Haas; Dr. Gunnar Spreen
• Cooperation Partner: Professor Dr. Hiroyuki Enomoto