Structure and Climatic Intra-Annual Variability of Water Mass Characteristics in the Powell Basin and on the Adjacent Antarctic Peninsula Shelf

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

Marine Hydrophysical Institute of RAS, Sevastopol, Russia

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

Abstract

The paper analyzes the long-term average structure and climatic intra-annual variability of water mass characteristics in the Powell Basin and adjacent water areas based on monthly average potential temperature and salinity data for each year from 1958 to 2021 from ECMWF ORA-S5 reanalysis. It is shown that the Antarctic Shelf Water is observed not only over the shallow shelf of the Joinville Archipelago, but also over the continental slope in the northwestern Weddell Sea. It is revealed that the layer of Circumpolar Deep Water is divided into Upper and Lower modifications. The Deep and Bottom Waters of the Weddell Sea do not appear as separate extremes on the long-term average θ,S-curves. It is shown that in the center of the cyclonic gyre in the Powell Basin, the Antarctic Winter Water core is located in a layer of 25–55 m. In the Scotia Sea, the Hesperides Trough, and over the Philip Ridge, the Antarctic Winter Water core deepens to 60–85 m. The minimum depths of the cores of the Upper and Lower modifications of the Circumpolar Deep Water (250–300 m and 500–600 m, respectively) are observed in the central part of the Powell Basin and closer to the center of the Weddell Sea Gyre, the maximum depths (1000– 1300 m and 1100–1500 m, respectively) are observed over the slopes of the depths of the Joinville shelf and the South Scotia, Philip, and Joinville Ridges. It is shown that seasonal changes in the θ-index of the Antarctic Surface Water are maximum (3.5–4°С) in the southern Scotia Sea and in the Hesperides Trough. Seasonal changes in the S-index are maximum (1.8–1.9 PSU) over the Philip Ridge and in the northern and southern parts of the Powell Basin. Intra-annual changes in the θ,S-indices of the Antarctic Shelf Water reach 1.6–1.8 °C and 1.5 PSU, respectively. The Weddell Sea Surface Water is characterized by weak changes in the θ-index, while changes in its S-index reach almost 1.8 PSU. Intra-annual changes in the θ,S-indices of Antarctic Winter Water are maximum in the central part of the Powell Basin (up to 1 °С and 1.1 PSU).

Keywords

Southern Ocean, Weddell Sea, Powell Basin, Antarctic shelf, water masses, potential water temperature, salinity, neutral density, spatiotemporal variability, vertical water structure

Acknowledgments

The work was carried out under FSBSI FRC MHI state assignment FNNN-2021-0004 «Fundamental studies of oceanological processes which determine the state and evolution of the marine environment influenced by natural and anthropogenic factors, based on observation and modeling methods» («Oceanological processes» code).

For citation

Artamonov, Yu.V., Skripaleva, E.A. and Nikolskii, N.V., 2023. Structure and Climatic Intra-Annual Variability of Water Mass Characteristics in the Powell Basin and on the Adjacent Antarctic Peninsula Shelf. Ecological Safety of Coastal and Shelf Zones of Sea, (3), pp. 22–39.

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