Abstract
Abstract. We use reanalysis data and satellite remote sensing of cloud properties to examine how meteorological conditions alter the surface energy balance to cause surface melt that is detectable in satellite passive microwave imagery over West Antarctica. This analysis can detect each of the three primary mechanisms for inducing surface melt at a specific location: thermal blanketing involving sensible heat flux and/or longwave heating by optically thick cloud cover, all-wave radiative enhancement by optically thin cloud cover, and föhn winds. We examine case studies over Pine Island and Thwaites glaciers, which are of interest for ice shelf and ice sheet stability, and over Siple Dome, which is more readily accessible for field work. During January 2015 over Siple Dome we identified a melt event whose origin is an all-wave radiative enhancement by optically thin clouds. During December 2011 over Pine Island and Thwaites glaciers, we identified a melt event caused mainly by thermal blanketing from optically thick clouds. Over Siple Dome, those same 2011 synoptic conditions yielded a thermal-blanketing-driven melt event that was initiated by an impulse of sensible heat flux and then prolonged by cloud longwave heating. The December 2011 synoptic conditions also generated föhn winds at a location on the Ross Ice Shelf adjacent to the Transantarctic Mountains, and we analyze this case with additional support from automatic weather station data. In contrast, a late-summer thermal blanketing period over Pine Island and Thwaites glaciers during February 2013 showed surface melt initiated by cloud longwave heating and then prolonged by enhanced sensible heat flux. One limitation thus far with this type of analysis involves uncertainties in the cloud optical properties. Nevertheless, with improvements this type of analysis can enable quantitative prediction of atmospheric stress on the vulnerable Antarctic ice shelves in a steadily warming climate.
Highlights
The contribution of West Antarctic mass loss to sea level rise, presently the second largest cryospheric contribution to sea level rise after the Greenland Ice Sheet (Mouginot et al, 2019; Rignot et al, 2019), is driven by a complex mechanical and thermodynamic system involving grounded ice sheets, their floating ice shelf extensions, and the surrounding ocean and atmosphere
We identify the Antarctic surface melt events with a standard passive microwave (PMW) technique using the Defense Meteorological Satellite Program Special Sensor Microwave Imager/Sounder (SSMIS), but with a new NASA-supported Making Earth System Data Records for Use in Research Environments (MEaSUREs) data product archived at the National Snow and Ice Data Center (NSIDC)
In this study we demonstrate that readily available climatic data, including meteorological reanalysis and satellite remote sensing, can be used to examine and diagnose individual episodes of surface melt over Antarctic ice sheet and ice shelf locations that are of significant concern in a steadily warming climate
Summary
The contribution of West Antarctic mass loss to sea level rise, presently the second largest cryospheric contribution to sea level rise after the Greenland Ice Sheet (Mouginot et al, 2019; Rignot et al, 2019), is driven by a complex mechanical and thermodynamic system involving grounded ice sheets, their floating ice shelf extensions, and the surrounding ocean and atmosphere. While a warming ocean causes a retreat of West Antarctic Ice Sheet grounding lines on numerous reverse slopes, by gradually accelerating the ice sheet outflow via the well-known marine ice sheet instability (Weertman, 1974; Oppenheimer, 1998; Joughin et al, 2014; Alley et al, 2015), the ice shelves mitigate this outflow through the buttressing they provide by being in contact with adjacent land masses (Fürst et al, 2016). Ghiz et al.: Energetics of surface melt in West Antarctica
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