δ18O as a tracer of the main regularities of water mass mixing and transformation in the Barents, Kara, and Laptev seas

Abstract

When researching the mixing of two or more water masses and their subsequent transformation, ideally, the most conservative parameters are used. Since the 1970s, the isotopic parameter δ18O has been used in various oceanological research works for example: Ostlund and Hut (1984) [J. Geophys. Res., 89, 6373–6381] and many others.The use of the salinity value and δ18O allowed the construction of a three-component system (“classic”) of equations (TSC). Nevertheless, in the work: Dubinina et al. (2019) [Okeanologiya, No. 1, 57. 38–48] it was demonstrated that “the application of the three-component mixing to modified waters causes an overestimation of river water input”. A model of ‘mixing-modification’, which eliminated this drawback, was presented in the work and the difference of estimation with the three-component system may be up to 20%. In the present study are also shown that the classic three-component system is fully applicable only under the conditions of ice melting, and under the conditions of ice formation estimates based on the three-component system give overestimated results of basic waters content in the final water mass. However, the methodology of sea water component composition estimation in this work differs slightly from the methodology presented in the above publication. A modified three-component system (TSM) presented in this work allows elimination of such inaccuracies. The difference between average values for the available series of observations according to TSC and TSM increases in the following order: Kara Sea > Laptev Sea > Barents Sea and the maximum difference for Atlantic waters and river waters (30.5% and 25.2%, respectively) was observed for Laptev Sea; 17.6% and 9.5%, respectively, for the Barents Sea and 16.3% for both components of the Kara Sea.To reveal newly formed water masses, a method of cluster analysis was applied. The composition of basic waters in the final water masses of the seas in question was obtained, as well as the values of these waters modification during ice formation or ice melting. General regularities of water masses formations in the discussed seas are delineated. An illustration of the average values of these magnitudes in water masses (clusters) in the system of coordinates content of: Atlantic Waters – river water– ice water for each sea had similar character, but their magnitudes differed depending on the different magnitude of the river runoff and different extent of these waters’ modification during ice formation and ice melting.It is noteworthy that the value of “ice water” has an important scientific and practical significance, because it is used to summarise singular cycle values, and possibly, several observation cycles of ice formation while also being unique, maintaining the “memory” of the ice formation process values, which occurred in these waters.