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Interannual Change in Mode Waters: Case of the Black Sea
Author(s) -
Stanev Emil V.,
Chtirkova Boriana
Publication year - 2021
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1029/2020jc016429
Subject(s) - halocline , ocean gyre , thermohaline circulation , potential vorticity , climatology , baroclinity , geology , ocean dynamics , stratification (seeds) , mesoscale meteorology , geopotential , mode water , potential temperature , atmospheric sciences , thermocline , advection , geopotential height , oceanography , vorticity , ocean current , vortex , meteorology , physics , salinity , biology , germination , thermodynamics , precipitation , seed dormancy , subtropics , botany , dormancy , fishery
More than 6,000 profiles from profiling floats in the Black Sea over the 2005–2020 period were used to study the ventilation of this basin and the mixing pathways along isopycnals. The layer of the minimum potential vorticity (PV), the Black Sea pycnostad, approximately follows the core of the cold intermediate layer, similar to the case of oceanic mode waters. However, unlike in the ocean, the horizontal patterns of PV are shaped by cyclonic gyre circulation. There is a principle difference in the probability distribution of the thermohaline properties presented in geopotential coordinates from those presented in density coordinates. In the latter case, several mixing pathways, which are not known from previous studies, dominate the ocean states. These formed after three intermittent events of cold water formation. The density ratio decreased three times during the last 15 years, revealing the decreasing role of temperature in the vertical layering of the Black Sea halocline. The basin‐wide distribution of PV above σ θ = 16, which is where the maximum vertical density gradient appears, is opposite to the distribution below this depth. This finding suggests a complex change in the mesoscale dynamics in different layers. Comparisons of observations with data from the Copernicus Black Sea operational model demonstrate that the mixing parameterizations of models need further improvements.