Abstract
Abstract. Surface snowmelt in the pan-Antarctic region, including the Antarctic ice sheet (AIS) and sea ice, is crucial to the mass and energy balance in polar regions and can serve as an indicator of climate change. In this study, we investigate the spatial and temporal variations in surface snowmelt over the entire pan-Antarctic region from 2002 to 2017 by using passive microwave remote sensing data. The stable orbits and appropriate acquisition times of the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) and the Advanced Microwave Scanning Radiometer 2 (AMSR2) enable us to take full advantage of daily brightness temperature (Tb) variations to detect surface snowmelt. The difference between AMSR-E/2 ascending and descending 36.5 GHz Tb values in vertical polarization (DAV36) was utilized to map the pan-Antarctic region snowmelt, as this method is unaffected by snow metamorphism. We evaluated the DAV36 algorithm against ground-based measurements and further improved the method over the marginal sea ice zone by excluding the effect of open water. Snowmelt detected by AMSR-E/2 data was more extensive and persistent than that detected by the Special Sensor Microwave/Imager (SSM/I) data. Continuous melt onset (CMO) ranged from August in the marginal sea ice zone to January in the Antarctic inland, and the early transient melt events occurred several days to more than 2 months earlier. The pan-Antarctic region CMO was significantly correlated (R=0.54, p<0.05) with the summer Southern Annular Mode (SAM). The decreased AIS melt extent was very likely linked (R=-0.82, p<0.01) with the enhanced summer SAM.
Highlights
Surface snowmelt on sea ice and ice sheets has a great influence on the energy exchange between the snow surface and atmosphere because wet snow has a lower albedo and absorbs more incoming solar radiation than dry snow (Steffen, 1995)
The Continuous melt onset (CMO) ranges from August in the marginal sea ice zone to January in the Antarctic inland, and the pan-Antarctic region EMO arrived 53 d earlier on average (Table 1)
We investigated the pan-Antarctic region surface melting conditions for 2002–2017 by using daily AMSR-E/2 observations
Summary
Surface snowmelt on sea ice and ice sheets has a great influence on the energy exchange between the snow surface and atmosphere because wet snow has a lower albedo and absorbs more incoming solar radiation than dry snow (Steffen, 1995). Meltwater may fill in the ice crevasses on ice sheets and migrate to the ice–bedrock surface, which can induce the acceleration of ice flow (Zwally et al, 2002; Sundal et al, 2011). Meltwater can transport heat into crevasses and deepen them, providing the conditions for ice shelves to break up through hydrofracturing (Scambos et al, 2000; van den Broeke, 2005). The spatial and temporal dynamics of surface snowmelt on sea ice and ice sheets have a direct effect on mass and energy balances in polar regions (Picard and Fily, 2006; van den Broeke et al, 2009; Stroeve et al, 2014). The timing and extent of surface snowmelt are indicators of changes in polar climate
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