Recent Antarctic Sea Ice Surface Melt from Satellite Remote Sensing (REASSESS)
Dr. Larysa Istomina
Institut für Umweltphysik
Abteilung für Erdfernerkundung
In January 2017, an unprecedented sea ice surface melt event has 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 appeared in the vicinity of these two stations also in summer 2017/2018. Melt ponds, puddles of melt water on top the sea ice, are common in the Arctic during summer. In the Antarctic, the melt ponds on sea ice are thought of as extremely rare. However, in the recent years many Antarctic research stations report unusually high summer air temperatures of just below or even above 0°C, so that the glaciers at sea level are melting in summer. However, till now, no study has been performed to detect and quantify melt ponds over Antarctic sea ice in the vicinity of the melting glaciers. In this project, we propose to use a melt pond detection algorithm successfully applied in the Arctic, and quantify Antarctic melt pond fractions from 2002 onwards using optical satellite data. The motivation for such a study is manifold: 1. Energy balance in the changing climate - the presence of surface melt introduces a drastic change to the amount of the energy reflected back into the atmosphere and transmitted into the ocean. Accurate melt pond and albedo datasets are therefore needed as input for climate models. 2. Sea ice concentration (SIC) algorithms – the passive microwave SIC algorithms are compromised in the presence of surface melt, as well as sea ice area dataset resulting from these SIC data. No correction for melt ponds is currently available. 3. The under-ice ecosystem - as the sea ice transmittance increases drastically in the presence of surface melt, the amount of the sunlight and potentially the amount of nutrients which are available to the under ice ecosystems increases and may lead to an ecosystem change.Within the project, we plan to test the following hypotheses: H1: The Antarctic sea ice is currently changing towards developing more melt ponds. Especially affected is the landfast sea ice near glaciers which are known to melt recently. H2: The recent Antarctic SIC and ice area dataset is incorrect due to overlooked melt ponds which are detected as open water. H3: The spectral albedo of Antarctic landfast ice differs from that of pack ice, and shows a negative trend in the recent years. The main outcome of the project is the dataset of melt pond fraction and spectral albedo of the Antarctic sea ice obtained from optical sensors with spatial resolution of 250- 300m. The resulting melt pond fraction dataset will for the first time allow to quantify Antarctic surface melt events both recorded and overlooked in the past, assess their temporal change and role for the climate state of the Antarctic sea ice zone, and provide corrected SIC and ice area datasets for climate models.
DFG Programme: Infrastructure Priority Programmes