Features of Hydrological Regime nearby the Pacific Coast of the Northern Kuril Islands Based on Ship Oceanographic Surveys

G. V. Shevchenko1, 2, ✉, V. N. Chastikov1, V. A. Ulchenko3

1 Sakhalin Branch of Russian Federal Research Institute of Fisheries and Oceanography, Yuzhno-Sakhalinsk, Russian Federation

2 Institute of Marine Geology and Geophysics, Far Eastern Branch of Russian Academy of Sciences, Yuzhno-Sakhalinsk, Russian Federation

3 Russian Federal Research Institute of Fisheries and Oceanography, Moscow, Russian Federation

✉ e-mail: Shevchenko_zhora@mail.ru

Abstract

Purpose. This study aims to examine the vertical distributions of temperature, salinity, and geostrophic currents along repeated sections during different seasons, based on oceanographic survey data.

Methods and Results. The analysis is based on data from seven surveys conducted in spring (May), summer (July–September), and autumn (November) along four selected transects crossing the shelf and continental slope off the southeastern coast of Kamchatka, the Fourth Kuril Strait, and the Severgin Strait. Variations in the surface heated layer, as well as in the cold and warm intermediate layers, are assessed. It is shown that in spring and autumn, the cold intermediate layer extends throughout the water column, whereas in the deep-sea area, it is underlain by a warm intermediate layer. In autumn, the upper boundary of the cold intermediate layer deepens, likely due to wind-wave mixing. Freshened water (with salinity as low as 31.5 PSU), resulting from ice melt in the Bering Sea, is observed off the southeastern coast of Kamchatka in July. However, salinity in the study area remains generally high. Calculated geostrophic current velocities indicate that a consolidated southwestward flow, extending through the entire water column and most pronounced above the slope, is observed only in spring—likely a remnant of winter circulation patterns. In summer and autumn, currents are more variable, with different directions in different layers and along various parts of the transects.

Conclusions. The analysis of oceanographic survey data demonstrates that the underwater Vityaz Ridge significantly influences the hydrological conditions in the Northern Kuril Islands region. Specifically, warm intermediate layer waters weakly penetrate into the northern part of the trough between the ridge and the Kuril Islands, while the cold intermediate layer develops down to depths of 500 m. In this area, current directions often differ from those over the continental slope. Although rare, negative seawater temperatures are occasionally recorded in the cores of the cold intermediate layer. The Kamchatka and Kuril currents are clearly defined in spring and become weaker during summer and autumn.

Keywords

northern Kuril Islands, seawater temperature, salinity, oceanographic section, Kamchatka Current, Kuril Current, cold intermediate layer, warm intermediate layer

Acknowledgements

This work was carried out within the framework of the state assignment of FSBSI VNIRO under the theme: “Regular observations of the distribution, quantity, quality, and reproduction of aquatic bioresources that are the objects of fisheries, as well as their habitat”.

Original russian text

Original Russian Text © G. V. Shevchenko, V. N. Chastikov, V. A. Ulchenko, 2025, published in MORSKOY GIDROFIZICHESKIY ZHURNAL, Vol. 41, Iss. 2, pp. 229–246 (2025)

For citation

Shevchenko, G.V., Chastikov, V.N. and Ulchenko, V.A., 2025. Features of Hydrological Regime nearby the Pacific Coast of the Northern Kuril Islands Based on Ship Oceanographic Surveys. Physical Oceanography, 32(2), pp. 253-269.

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