Microwave Emission Signals Tracking the Collapse of Conger Ice Shelf

Ice shelf collapses are significant because they are an indication of a change in the environmental balance at the edge of a glacier that has allowed the ice shelf to develop. Despite the shrinking during recent years, Conger ice shelf on the east side of Antarctica had remained intact through the previous austral summer seasons. However, in March 2022, the ice shelf reached a breaking point and collapsed. We set out to investigate what spaceborne microwave radiometer measurements can reveal about the Conger ice shelf integrity leading up to the breakup. The microwave emission reaching the surface of an ice shelf, and then detected with a spaceborne radiometer, can be originated from hundreds of meters deep in the ice shelf, or right from the ice-sea interface at the bottom of the ice shelf, depending on the frequency. The lower frequencies propagate easier through the medium than higher frequencies so the lower frequencies carry information from deeper than the higher frequencies. Correspondingly, the lower frequencies are less sensitive to features affecting the higher frequencies. As a result, the observations at different frequencies are highly complementary. This is the case when combining NASA Soil Moisture Active Passive (SMAP) 1.4 GHz with JAXA Advanced Microwave Scanning Radiometer 2 (AMSR2) 6.9, 10.7, 18.9 and 36.5 GHz measurements. The multi-year and twice-daily observations over Conger ice shelf show the intensity of the daily-scale surface melting events as well as indications on longer term alterations deeper in the ice shelf leading up to the collapse. Moreover, the multi-frequency emission trends revealed in the analysis of the Conger breakup can be instructive in the investigation of the integrity of other ice shelves.