Three-Dimensional Identification of the Black Sea Mesoscale Eddies according to NEMO Numerical Model Calculations

Abstract

A new method of three-dimensional identification of mesoscale eddies based on the results of the Black Sea hydrodynamics modeling is applied. It is based on identification of the closed streamlines in the velocity fields. This method and the data resulted from the NEMO calculations for [2005][2006][2007][2008] are used to identify more than 1000 mesoscale eddies in the basin. The results permit to define eddy characteristic trajectories, calculate spatial variability of their velocities and radii and frequency of detection of cyclones and anticyclones. The obtained results are in good agreement with the earlier published studies of the eddy characteristics derived from satellite and in situ data. The modeling results permit to investigate the features of vertical distribution of eddy characteristics. The eddies are most often detected in the 0-150 m layer (the highest detection frequency F is within 20-50 m). In the 150-300 m layer this value is two times smaller, but still is substantial. Below 300 meters F quickly decreases with depth. The analogous distribution is characteristic of the eddy radii and orbital velocity: the highest values are observed in the upper 0-150 m layer, and in the lower layers they sharply decrease with depth. The analysis of seasonal variability of the eddy characteristics shows that the anticyclonic dynamics intensifies in summer, whereas the cyclonic one -in winter, that is consistent with the previous studies. The developed method provides additional opportunities for investigating the features of the eddy generation and evolution in the Black Sea.

Seasonal and Vertical Variability of Currents Energy in the Sub-Mesoscale Range on the Black Sea Shelf and in Its Central Part

“…E sp in all seasons is maximum in the ML, the depth of which varies from 5-10 m in summer to 50 m in winter [34,35]. This relationship is also observed on an interannual scales.…”

Seasonal and Vertical Variability of Currents Energy in the Sub-Mesoscale Range on the Black Sea Shelf and in its Central Part

“…6, b; 7, b). Анализ численных результатов показал, что вероятной причиной такого усиления является адвекция опресненных реками вод в центр СЗШ под действием интенсифицирующихся в летний период синоптических вихрей [35]. Увеличение потенциальной энергии вод, а также горизонтальная неоднородность распределения солености вызывает интенсивную генерацию бароклинных субмезомаштабных вихрей.…”

Eddy Induced Cross-Shelf Exchanges in the Black Sea

“…The south-eastern Black Sea has major rivers such as the Kodori, Rioni, Inguri, Çoruh, Kızılırmak, and Yeşilırmak Rivers, providing nutrients [40,41], and hence a higher productivity to the shelf. Particularly in the narrow shelf of Georgia, riverine discharge is important as it is very close to the open waters, and therefore much easier for the shelf waters to be transported offshore via shelf-break eddies and filaments [8,26,[42][43][44], especially in the presence of strong winds. Local winds are an important component of the wind forcing, which are; the tip jets near Cape Fener and the Kolkheti Valley winds around the Caucasian Mountains [45].…”

“…The aforementioned studies have focused on different parts of the Black Sea and studies focusing on cross-shelf transport in the south-eastern Black Sea are limited. Previous studies have focused on eddies in this region and their variability [43,48] and presented snapshots of cross-shelf transport, but have not investigated them in any detail. Furthermore, the interannual and seasonal variability of cross-shelf exchanges and their causes have not been studied previously in the Black Sea, with the exception of the north-western shelf [34], and is of importance to understand the nutrient and ecosystem dynamics of the south-eastern Black Sea.…”