Water Masses in the Western Part of the Chukchi Sea in August 2019 and Their Hydrochemical Features

Abstract

The distribution of water masses in August 2019 in the Chukchi Sea, and their hydrochemical features are i-nvestigated using shipboard data from the transarctic expedition onboard the R/V Professor Levanidov. The work was carried out in the southern shallow part of the sea and in the northern part of the sea outside the 70-meter isobath. Six main water masses were identified: Alaskan and Anadyr Coastal Water (ACW), Siberian Coastal Water (SCW), Melt Water (MW), Summer Bering Sea Water (BSW), Remnant Pacific Winter Water (RWW) and Atlantic Water (AW). Their features are described and analyzed. It was revealed that the water masses of the Chukchi Sea are characterized by a high spatial variability of hydrochemical parameters, especially the BSW, RWW and AW. In the southern part of the Chukchi Sea the presence of very high values of ammonium nitrogen in the bottom layer was noted (up to 12.6 µM). In august 2019, transformed AW, typically residing below 150 m, were observed at a depth of 117–137 meters, characterized by salinity values from 34.2 to 35.7, high content of mineral silicon (93–97 µM), low elevated values of apparent oxygen utilization (240–270 µM), and unusually low N* (a measure of the fixed nitrogen excess relative to phosphorus) values (down to −24.0 µM). At the same time, the AW observed at depths below 140 m did not have such hydrochemical features.