Long-Term Observation of the Arctic Sea Ice Melt Onset from Microwave Radiometry
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RESEARCH ARTICLE
Long-Term Observation of the Arctic Sea Ice Melt Onset from Microwave Radiometry Rajkumar Kamaljit Singh1
•
Thoudam Vilip Singh2 • Urikhinbam Somas Singh2
Received: 13 December 2019 / Accepted: 20 October 2020 Ó Indian Society of Remote Sensing 2020
Abstract An exercise is carried out to analyse the variability in the Arctic snowmelt onset dates (SMOD) using 34 years of passive microwave radiometry data. For this study, the sea ice prevailing regions above 40° N have been clustered into thirteen sectors. Trend analysis of the SMOD shows that 10 sectors have negative trends meaning earlier melt onsets. Negative trends in the East Siberian Sea, Kara Sea, Laptev Sea, Chukchi Sea, Central Arctic Ocean, Canadian Archipelago, Beaufort Bay and Barents Sea are all statistically significant. Although the Greenland Sea shows a statistically significant positive trend is obtained. Inter-sectorial correlation shows strong positive correlations in many sectors such as between the Canadian Archipelago and the Central Arctic, Chukchi Sea—Central Arctic, East Siberian-Central Arctic. Moreover, correlation with the Arctic Oscillation (January to March average) shows negative correlations with the SMOD. Keywords Snowmelt onset Trend analysis Arctic oscillation
Introduction The event in the summer melt season whereby, the snow layer above the surface of sea ice starts melting, is termed as the snowmelt onset (Meier and Markus 2015; Peng et al. 2018). It is one of the important global climate indicators. During this event, there is a reduction in the surface albedo. This, in turn, leads to more absorption of solar radiation by the ice and ocean, increasing melting throughout the melt season (Curry et al. 1995; Bliss et al. 2017). Arctic melting season is found to become longer by many investigators (Belchansky et al. 2004; Stroeve et al. 2006, 2014; Markus et al. 2009). Bliss and Anderson (2014), Peng et al. (2018) have found a shift towards earlier & Rajkumar Kamaljit Singh [email protected] Thoudam Vilip Singh [email protected] Urikhinbam Somas Singh [email protected] 1
Department of Physics, Manipur Technical University, Takyelpat, Imphal, Manipur, India
2
Department of Physics, National Institute of Technology Manipur, Langol, Imphal, Manipur, India
annual melt onset for most of the Arctic in the period from 1979 to 2016, except for the Bering Sea and smaller areas of Hudson Bay, Canadian Archipelago and the Sea of Okhotsk. There is a transient increase in the microwave emissivity of the snow when it turns to liquid water. Correspondingly, brightness temperature will also increase suddenly. The acquired microwave brightness temperature, TB, at a given frequency and polarisation depends on the surface emissivity at that given frequency and polarisation, and also on the physical temperature of the target. In a more technical term, snowmelt onset corresponds to the point where microwave brightness temperatures rise sharply because of the introduction of water in the liquid fo
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