A large (80-90 km in diameter) anticyclonic eddy centered at 43°N, 37-38°E has been the subject of complex investigation in the summer-autumn of 1999 based on measurements carried out during the ''Black Sea'99'' expedition on board of R/V Akvanavt (CTD surveys, deployment of Argos-tracked drifters), analysis of satellite imagery, and using altimetric sea level anomaly maps from merged TOPEX/POSEIDON and ERS-2 satellite data. The eddy was formed as a nearshore anticyclonic eddy (NAE) in the Sochi-Sukhumi region, separated from the coast on 6-9 April 1999, stayed at the center of the eastern basin, which is usually characterized by cyclonic circulation, during about 8 months and decayed near the Turkish coast in December 1999. A compilation of hydrodynamic situations of different years (1993,(1997)(1998)(1999) suggests that similar open sea anticyclonic eddies are frequently the elements of the circulation in the eastern Black Sea in the warm season (April-December). A positive correlation appears to be between eddies' formation and weak macroscale circulation associated with low atmospheric wind forcing. Long lifetime of open sea anticyclones is likely determined by their interaction with neighboring eddies. NAEs' separation from the coast and their transformation into open sea eddies provide horizontal mixing of the upper layer waters and results in deflection of the Rim Current offshore, formation of large meanders of the current around the eddies, and its branching when rounding such features. An example of calculation of cross-shelf water transport relating to an offshore Rim Current branch is presented. It is pointed out that an estimation of the shelf/open sea water exchange based on the box balance model does not contradict the assumption that such exchange is considerably determined by NAEs' separation from the coast.
Caspian Sea level (CSL) has undergone substantial fluctuations during the past several hundred years. The causes over the entire historical period are uncertain, but we investigate here large changes seen in the past several decades. We use climate model‐predicted precipitation (P), evaporation (E), and observed river runoff (R) to reconstruct long‐term CSL changes for 1979–2015 and show that PER (P‐E + R) flux predictions agree very well with observed CSL changes. The observed rapid CSL increase (about 12.74 cm/yr) and significant drop (~−6.72 cm/yr) during the periods 1979–1995 and 1996–2015 are well accounted for by integrated PER flux predictions of ~+12.38 and ~−6.79 cm/yr, respectively. We show that increased evaporation rates over the Caspian Sea play a dominant role in reversing the increasing trend in CSL during the past 37 years. The current long‐term decline in CSL is expected to continue into the foreseeable future, under global warming scenarios.
Sea surface temperature (SST) derived from the weekly measurements made by the (Belkin and Gordon, 1996), although some details are different (in particular the larger zonal extent of the NSTF and the wider frontal SST ranges than previously observed).A good correspondence of the measurements made during two hydrographic surveys in the Kerguelen region (22 January-3 February 1999) and in the Tasmania region (3-22 March 1998) with satellite SST and SST gradient maps was found.
Observations of giant ice rings on Lake Baikal (Russia) have recently sparked scientific and public interest. However, there is still no clear consensus on their origins. Here, we provide an inventory of the ice rings based on satellite imagery and photography for 1974-2014. We have identified 45 rings on Lake Baikal (compared with 13 previously known) and also for the first time four rings for the neighbouring Lake Hovsgol (Mongolia). The results of our hydrographic surveys beneath the ice rings in Lake Baikal in 2012-2014 and in Lake Hovsgol in 2015 show the presence of warm double-convex lens-like eddies before and during manifestation of ice rings. We suggest that these eddies are the driving factor for the formation of ice rings in these lakes. We reassess the existing hypotheses of ice ring formation and discuss the potential mechanisms of eddy formation.
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