Seasonal, interannual, and mesoscale variability of the Black Sea upper layer circulation derived from altimeter data

Abstract

[1] TOPEX/Poseidon and ERS altimeter data comprising the period from May 1992 to May 1999 are assimilated into a shallow water model for providing a dynamically consistent interpretation of the sea surface height variations and estimation of the temporal and spatial characteristics of the upper layer circulation in the Black Sea. These 7-yearlong observations offer a new capability for interpretation of major transient and quasipermanent features of the upper layer circulation. The instantaneous flow fields involve a complex, eddy-dominated system with different types of structural organizations in which the eddies and the gyres of the interior cyclonic cell interact continuously among themselves and with meanders, and filaments of the Rim Current. The circulation possesses a distinct seasonal cycle whose major characteristic features repeat every year with some year-to-year variability. An organized two-gyre winter circulation system disintegrates gradually into a series of interconnecting eddies in the summer and autumn months, which are also characterized by more pronounced and complex mesoscale activity in the peripheral flow system. Our analyses suggest a revised schematic circulation picture of the major quasi-permanent and recurrent elements of the Black Sea.

Small river plumes off the northeastern coast of the Black Sea under average climatic and flooding discharge conditions

“…After the sediment particle settles beneath the plume, its movement is governed by ambient coastal circulation, reproduced by the INMOM model. The similar con-figuration of coupled Eulerian (Princeton Ocean Model) and Lagrangian (STRiPE) models was recently used for simulation of the delivery and fate of fluvial water and terrigenous sediments discharged by the Peinan River at the southeastern coast of the island of Taiwan under freshet and typhoon discharge conditions (Osadchiev et al, 2016) and for studying the dynamical features of the Zhuoshui and Wu river plumes located on the western coast of Taiwan (Korotenko et al, 2014). (Volodin et al, 2010) as well as for modeling the Arctic Ocean (Johnson et al, 2012) in the framework of the Arctic Ocean Model Intercomparison Project, and the South Ocean Farneti et al, 2015) and North Atlantic Ocean (Danabasoglu et al, 2016) in the framework of the Coordinated Ocean-ice Reference Experiments.…”

Untitled

“…The surface current fields after 24 and 48 hours (time is counted from the initial moment of the forecast, 00:00 h, 25.07.2011), predicted by the RM-IG, are presented in Figure 2a and 2b, respectively and the same fields predicted by the BSM of MHI at the same time moments are shown in Figure 2c other calculations show also that in most cases the Batumi eddy is the main component of the summer regional circulation in the Easternmost part of the Black Sea. This feature of the regional circulation in warm season is known from observations (Korotaev et al, 2003). Comparison of circulation patterns predicted from RM-IG and BSM of MHI shows that the main differences are in the zone with width about 30-35 km along the Caucasus shoreline.…”

Untitled

“…The circulation is composed of a meandering, cyclonic Rim current and two cyclonic cells within the interior basin ( Figure 1). This general circulation is known to have a seasonal cycle, with its characteristic features repeating every year with some year-to-year variability (Korotaev et al, 2003). In addition, the mesoscale circulation is characterized by a number of anticyclonic eddies forming on the coastal side of the Rim Current: Bosphorus, Batumi, Sukhumi, Caucasus, Kerch, Crimea, Sevastopol, Danube, Constantsa, and Kaliakra eddies (Figure 1).…”

“…Current speeds in the upper layer of the Rim current are 50-150 cm/s (Oguz and Besiktepe, 1999) and meanders of the Rim Current have a typical time scale of Figure 1. Schematic of the Black Sea general surface circulation (reproduced from Korotaev et al, 2003). Names of quasipermanent anticyclonic eddies are indicated with arrows on land near by.…”

“…This weekly data was then interpolated to obtain daily sea surface height fields. The mean sea surface height provided by Korotaev et al (2003) was then added to the daily AVISO fields to compute the geostrophic flow at the surface. Using only surface circulation fields in this study is a reasonable assumption for anchovy in the Black Sea, because eggs and larvae are found in the upper 10-20 m, above the seasonal thermocline, egg production not being possible in the Cold Intermediate Layer (~ 7°C) below the surface mixed layer (Niermann et al, 1994;Kideys et al, 1999;Satilmis et al, 2003).…”