Continental and sea ice melting signature in Arctic sea surface salinity

The warming of the Arctic air during summer is an increasingly frequent phenomenon. With surface air temperature exceeding more than 10ºC the mean of the last 40 years, and weekly average temperature values close to this peak value, the melt runoff in Greenland has dramatically increased. This phenomenon has reached its maximum expression in 2012 and 2019. The Greenland Ice sheet surface affected by melting has reached a maximum during these years (2012: 97%; 2019: 60%). The consequences of extreme ice melt episodes are critical not only for climate but also for coastal communities.

As the temperature raise is caused by transient meteorological conditions (i.e. warm air systems coming from the South) the melting processes takes place suddenly and lasts only few days: from July 8 to July 12 in 2012 and from July 30 to August 3 in 2019. Nevertheless the huge amount of fresh water poured into the ocean can be detected by the drastic changes in the surrounding sea surface salinity. Not only continental ice melting should change the coastal sea surface salinity, but also the sea ice melting should reflect a freshwater anomaly along the ice field edge.

ESA funded the Arctic+ salinity project which main objective is to retrieve Arctic sea surface salinity from Soil Moisture and Ocean Salinity (SMOS) mission measures. This new satellite salinity product provides remote sensing salinity measures in regions where insitu measures are very scarce and it offers an invaluable opportunity to study the ice melting simultaneously in the whole Arctic. Figure 1 shows preliminary evidences on the fact that this salinity product can resolve the increasing freshwater fluxes derived from continental and sea ice melting process.

Figure 1.- Impact of melting process in sea surface salinity around Greenland and Severny island. The data correspond to 9-day maps centered on August 22, 2019 in the Severny island case and centered on July 15, 2012 for Greenland case. Left: Difference with salinity provided by the annual World Ocean Atlas during period 2005-2017. Right: Sea surface salinity retrieved from SMOS measures in the mentioned periods. Note that in Severny island case part of the freshwater bloom could be provided by Yenisey and Ob’ rivers discharges.