Surface melt magnitude retrieval over Ross Ice Shelf, Antarctica using coupled MODIS near-IR and thermal satellite measurements

Abstract. Surface melt has been increasing over recent years, especially over the Antarctic Peninsula, contributing to disintegration of shelves such as Larsen. Unfortunately, we are not realistically able to quantify surface snowmelt from ground-based methods because there is sparse coverage of automatic weather stations. Satellite based assessments of melt from passive microwave systems are limited in that they only provide an indication of melt occurrence and have coarse spatial resolution. An algorithm was developed to retrieve surface melt magnitude using coupled near-IR/thermal surface measurements from MODIS were calibrated by estimates of liquid water fraction (LWF) in the upper 1 cm of the firn derived from a one-dimensional physical snowmelt model (SNTHERM89). For the modeling phase of this study, SNTHERM89 was forced by hourly meteorological data from automatic weather station data at reference sites spanning a range of melt conditions across the Ross Ice Shelf during a relatively intense melt season (2002). Effective melt magnitude or LWF_<eff> were derived for satellite composite periods covering the Antarctic summer months at a 4 km resolution over the entire Ross Ice Shelf, ranging from 0–0.5% LWF_<eff> in early December to areas along the coast with as much as 1% LWF_<eff> during the time of peak surface melt. Spatial and temporal variations in the magnitude of surface melt are related to both katabatic wind strength and advection during onshore flow.