Detecting Surface Melt Events on the West Antarctic Ice Sheet Via Passive Microwave Remote Sensing

Emma Renee Robertson, University of Massachusetts Amherst, Geoscience, Amherst, MA, United States and Dan Lubin, University of California San Diego, Scripps Institution of Oceanography, La Jolla, CA, United States
Abstract:
Warming ocean temperatures underneath coastal ice shelves have been the primary driver of volume loss from West Antarctic ice shelves. Surface melt is an important but lesser understood phenomenon and occurs sporadically over lower elevations of the West Antarctic Ice Sheet (WAIS). Decline in ice shelf volume has significant consequences for the stability of the WAIS and global sea-level rise. We investigated episodes of daily surface melt over a period of thirty-eight years (1978-2016) during the austral summer using Special Sensor Microwave Imager (SSMI and SSMI/S) data provided by the National Snow and Ice Data Center (NSIDC). We computed cold-season averages at each grid cell to determine threshold values using the 19 GHz horizontal channels on the 25-km Equal-Area Scalable Earth (EASE) Grid from the MEaSUREs Calibrated Enhanced-Resolution Passive Microwave Daily EASE-Grid 2.0 Brightness Temperature ESDR data set. High-resolution Image-derived Grounding and Hydrostatic Lines for the Antarctic Ice Sheet were used to determine grounding lines and locations of satellite pixels exactly on the ice shelves. A brightness temperature (Tb) 30K above the threshold (cold season average) value indicated the occurrence of a melt event. Preliminary analysis of brightness temperature data and satellite imagery observations has revealed that melt trends differ throughout regions. Ice shelves on the Antarctic Peninsula show trends of increasing melt until the year 2000 when a decreasing melt trend appears. Amundsen Sea region ice shelf melting trends appear to be more anomalous and do not follow the increase-decrease trend of the Antarctic Peninsula. Overall, the Antarctic Peninsula appears to experience a great number of melt days on average. The current West Antarctic climate allows for the sporadic occurrence of extensive melt events. Additional analysis will determine the physical processes that contribute to these melt events. Further research is necessary to improve understanding of melt events and develop models to predict future episodes.