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

• Published in: Oceanology (Washington. 1965) 2023-06, Vol.63 (3), p.314-324
• Main Authors: Kodryan, K. V., Kivva, K. K., Zubarevich, V. L., Pedchenko, A. P.
• Format: Article
• Language: English
• Subjects: Ammonium; Ammonium compounds; Coastal waters; Earth and Environmental Science; Earth Sciences; Expeditions; Isobaths; Marine Physics; Meltwater; Nitrogen; Oceanography; Phosphorus; Plankton; Seawater; Shallow water; Silicates; Spatial variations; Water masses
• ISSN: 0001-4370; 1531-8508
• DOI: 10.1134/S0001437023020078

The distribution of water masses in August 2019 in the Chukchi Sea and their hydrochemical features were investigated using shipboard data from the transarctic expedition on board the R/V Professor Levanidov . The work was carried out in the southern shallow-water part of the sea and in the northern part beyond the 70-m 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, in particular, the BSW, RWW and AW. In the southern Chukchi Sea, very high values of ammonium nitrogen in the bottom layer were noted (up to 12.6 µM). In August 2019, transformed AW, typically residing below 150 m, was observed at a depth of 117–137 m. This transformed AW had salinity values from 34.2 to 35.7 which are typical for AW, but anomalously high content of silicate (93–97 µM), low apparent oxygen utilization values (240–270 µM), and low N* (a measure of fixed dissolved inorganic nitrogen excess relative to dissolved inorganic phosphorus) values (down to −24.0 µM). At the same time, the AW observed at depths greater than 140 m did not have such anomalous hydrochemical features.