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Abstract <p>Methods of assessing isotopic (δD, δ<sup>18</sup>O) parameters of the freshwater component in the river–sea transition zone are considered based on materials sampled in late July 2016 along two meridional transects extending from the Ob and Yenisey river estuaries to the center of the Kara Sea. The isotopic parameters of the runoff from these rivers are contrasting (δ<sup>18</sup>O = –15.0 ± 0.3‰, δD = –112.7 ± 2.1‰ for the Ob and δ<sup>18</sup>O&#xa0;= –18.9 ± 0.6‰, δD = –142.2 ± 4.3‰ for the Yenisey). It has been shown that river waters within the seawater surface layer do not have time to homogenize. For instance, in the central part of the Yenisey transect crossing the Ob–Yenisey plume, the share of Ob water in the freshwater component (FC) is 60%. Within river estuaries, the FC is homogeneous only in the upper water layer (less than 5 m); with depth, variations in δ<sup>18</sup>O(FC) values reach 16‰ for the Gulf of Ob and 12‰ for Yenisey Bay, exceeding the annual seasonal variations in this value in river water. In the bottom layer for the estuarine zones of both rivers, we observe a uniform FC with isotope-light characteristics of regional atmospheric precipitation coming to the estuarine zone with Kara Sea waters.</p>

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Origin of the Freshwater Component in Estuaries of the Ob and Yenisey Rivers and Adjacent Waters of the Kara Sea Based on Isotopic (δD, δ18O) Data

  • 期刊论文

  • 发表日期：

    2025年2月1日

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  • S. A. Kossova,
  • Ye. O. Dubinina

摘要

Abstract

Methods of assessing isotopic (δD, δ18O) parameters of the freshwater component in the river–sea transition zone are considered based on materials sampled in late July 2016 along two meridional transects extending from the Ob and Yenisey river estuaries to the center of the Kara Sea. The isotopic parameters of the runoff from these rivers are contrasting (δ18O = –15.0 ± 0.3‰, δD = –112.7 ± 2.1‰ for the Ob and δ18O = –18.9 ± 0.6‰, δD = –142.2 ± 4.3‰ for the Yenisey). It has been shown that river waters within the seawater surface layer do not have time to homogenize. For instance, in the central part of the Yenisey transect crossing the Ob–Yenisey plume, the share of Ob water in the freshwater component (FC) is 60%. Within river estuaries, the FC is homogeneous only in the upper water layer (less than 5 m); with depth, variations in δ18O(FC) values reach 16‰ for the Gulf of Ob and 12‰ for Yenisey Bay, exceeding the annual seasonal variations in this value in river water. In the bottom layer for the estuarine zones of both rivers, we observe a uniform FC with isotope-light characteristics of regional atmospheric precipitation coming to the estuarine zone with Kara Sea waters.