Chapter 13 - Spatiotemporal variability of snowmelt onset across Svalbard inferred from scatterometer data (2000–2017)

Abstract

Significant changes in the interannual variation of Arctic snow and sea ice are connected to changes in the global climate. Retreat of ice sheets/glaciers is due to increased melting in many regions of the cryosphere. Active microwave sensors are frequently used to detect surface melting because of their sensitivity to the liquid water presence in snow/ice. We mapped the annual melt duration and summer melt onset for the Svalbard archipelago using microwave scatterometers flown on QuikSCAT, OSCAT, ASCAT, and OSCAT-2, providing one of the longest continuous records of radar backscatter to estimate snowmelt onset and melt duration on Svalbard spanning 2000–17. A single threshold-based model was used to detect the timing of snowmelt; the threshold was calculated using meteorological data from manned weather stations. The results capture the timing and extent of melt events caused by warm air temperature and precipitation, as a consequence of the influx of moist, mild air from the Norwegian and Barents seas. The highest melt duration and earlier melt onset occurred in southernmost and western Svalbard, in response to the influence of the warm West Spitsbergen Current. Compared to earlier studies, we found considerable interannual variability and regional differences. Though the record is short, there is an indication of an increasing trend in total days of melt duration and earlier summer melt onset date, possibly linked to the general warming trend. Climate indices such as Interdecadal Pacific Oscillation and Pacific Decadal Oscillation are well correlated with onset melt and duration across Svalbard. With the reported year-after-year decrease in sea ice cover over the Arctic Ocean, the trend toward longer snowmelt duration inferred from this study is expected to enhance the Arctic amplification.