Variations of convective waters originated in East Siberian shelves of the Arctic Ocean

Abstract

Large summer sea ice retreats have been observed over the East Siberian Sea (ESS) since the late 2000s. The retreats suggest enhanced oceanic convections during the subsequent freeze-up period and resultant cooling and salinization of shelf waters. In addition off-shelf intrusions of the convective shelf waters have a potential to deform upper halocline structures in the adjacent basin. Here we have examined spatial and temporal variations of the convective waters originated in shlef regions of the ESS using in situ data collected by IBRV ARAON in 2011-2018. The convective shelf waters, traced by near-freezing temperature at salinity of about 32.5, were observed over shelf margins of the ESS during the observational period. The waters were trapped to the shelf break near 70 m, and their core temperature were decreased in 2017-2018 compared with the previous level. Their seasonal behaviors around the shelf margins were also captured by two ocean moorings deployed in 2017-2018. The convective shelf waters with the near-freezing temperature appeared in the freezing period from November to May, but timing and corresponding salinity differed depending on mooring sites. We will also discuss possible mechanisms of these inter-annual and seasonal variations of the convective shelf waters associated with off-shelf/on-shelf intrusions.