Using δ18O as a Tracer of the Formation of Water Masses in the Laptev Sea. Part 2. Quantification of the Volume of Atlantic, River, and Melt Water as well as Water Withdrawn for Ice Formation

Abstract

The main characteristics of water masses in the Laptev Sea formed as a result of the mixing of Atlantic and river water and transformed as a result of ice formation and ice melting were revealed using the conservative isotopic parameter δ¹⁸O as a tracer. The amount of Atlantic, river, and melt water as well as the volumes of water withdrawn for ice formation are quantified for six water masses typical of the Laptev Sea. Both melt and transformed (as a result of ice formation) water types are present in the surface river water mass. The prevalence of melt water is observed in the range of sea water salinity from 0 to 7–8 psu. The maximum content of melt water in this salinity range can reach 40%, and the desalination resulting from ice melting reaches 0.2–0.7 psu. The areas with the maximum water removal for ice formation are linked to the position of summer and winter water of the Laptev Sea, in the area of the Anabar-Lena, East Taymyr, West New Siberian, and North New Siberian flaw polynyas and fast ice in the southeastern part of the sea. In these regions water removal for ice formation makes up 10 to 20% and is observed from the surface to the bottom even during the summer-autumn period. Atlantic water is characterized not only by mixing with river water from Siberian rivers but also by transformations resulting from ice formation. However, this effect is largely associated with the convective mixing with overlying layers where ice formation occurs. Mean temperature of the bottom layers of Arctic basin water is by 2.2°C lower than the mean temperature of Atlantic water, and mean salinity is by ~0.06 psu higher. In this water the presence of river water as well as the influence of ice formation and ice melting mass are less pronounced as compared to Atlantic water.