Climatic Variability of the Water Thermohaline Structure in the Weddell-Scotia Confluence

Yu. V. Artamonov, E. A. Skripaleva*, N. V. Nikolskii

Marine Hydrophysical Institute of RAS, Sevastopol, Russia

* e-mail: sea-ant@yandex.ru

Abstract

Based on the ECMWF ORA-S5 reanalysis data for 1958–2023, the paper analyses the average long-term structure of waters in the Weddell–Scotia Confluence and the climatic variability of its boundary characteristics. It is shown that this zone was most clearly manifested between Shishkov Island and the South Orkney Shelf. The northern boundary of this zone (Scotia Sea Front) was located above the southern slope of the South Scotia Ridge, and the southern boundary (Weddell Sea Front) was south of the Phillip Ridge. Both fronts were most intense in the 150–500 m layer. Near the South Orkney Shelf, the width of the Weddell–Scotia Confluence zone decreased by more than five times. The intensity of the fronts also weakened in the easterly direction, and they were mostly not traced east of the South Orkney Islands. On an interannual scale, the displacements of the Scotia Sea Front and the Weddell Sea Front in latitude did not exceed 0.5 degrees, while their intensity changed synchronously. From 1983 to 2010, a decrease in their intensity was observed, whereas from 1958 to 1982 and after 2010 there was an increase. In the time series of annual mean anomalies of temperature gradient values characterizing interannual changes in the intensity of the Scotia Sea Front and the Weddell Sea Front, a periodicity of 4 and 6 years was revealed. A significant positive correlation was found between the Antarctic Oscillation index and the interannual intensity anomalies of the fronts, with a phase lag of 0–3 years for the Weddell Sea Front and 3–5 years for the Scotia Sea Front. The tendency to increase the intensity of the Weddell–Scotia Confluence boundaries with an increase of the Antarctic Oscillation index values was especially clear over the past 10 years. During this period the high positive values of this index and maximum positive values of the Weddell Sea Front intensity anomalies were observed. Over the past 10 years, the Weddell–Scotia Confluence boundaries have strengthened markedly as the Antarctic Oscillation index increased. This period featured persistently high positive index values alongside maximum positive intensity anomalies in the Weddell Sea Front.

Keywords

Weddell Sea, Scotia Sea, potential sea water temperature, salinity, vertical water structure, water masses, thermohaline fronts, spatio-temporal variability, Antarctic Oscillation, South Oscillation

Acknowledgments

The work was carried out under FSBSI FRC MHI state assignment FNNN-2024-0014 “Fundamental studies of interaction processes in the ocean-atmosphere system forming the variability of the marine environment physical state on different spatio-temporal scales”.

For citation

Artamonov, Yu.V., Skripaleva, E.A. and Nikolskii, N.V., 2025. Climatic Variability of the Water Thermohaline Structure in the Weddell-Scotia Confluence. Ecological Safety of Coastal and Shelf Zones of Sea, (4), pp. 76–96.

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