scholarly journals Upwelling dynamics in the Baltic Sea studied by a combined SAR/infrared satellite data and circulation model analysis**The Envisat ASAR images used in this study were provided by ESA within the framework of the Envisat AO project C1P.3424, and C1P.8116. This work was supported by 1) the Russian Foundation for Basic Research grant 12-05-90807-mol rf nr, and 2) the Russian Government (grant No. 11.G34.31.0078) for research under the supervision of leading scientists at the Russian State Hydrometeorological University.

Oceanologia ◽  
2013 ◽  
Vol 55 (3) ◽  
pp. 687-707 ◽  
Author(s):  
Evgenia Gurova ◽  
Andreas Lehmann ◽  
Andrei Ivanov
2021 ◽  
Author(s):  
Maria Kostadinova-Avramova ◽  
Petar Dimitrov ◽  
Andrei Kosterov ◽  
Mary Kovacheva

<p>Numerous historical sources and archaeological monuments attest the age of Antiquity in Bulgaria – from both the early Roman period (I – III c.) and Late Antiquity (IV – VI c.). Owing to systematic archaeological excavations, lasting more than 100 years, plenty of information has been accumulated concerning not only all aspects and manifestations of its material culture, but also their evolution and chronology.  This in turn allows for interdisciplinary fields such as archaeomagnetism to progress.</p><p>There are many archaeomagnetically studied archaeological structures from the Antiquity. The results included in the Bulgarian database form 74 reference points. However, only 20 of them are full-vector determinations because 70 % of the investigated materials are bricks. Hence, the secular variation of declination is poorly constrained within the considered period. Moreover, the reuse of bricks in the constructions occurred quite often (especially in the Late Antiquity) providing for possible errors in archaeological dating. In addition, stronger effects of magnetic anisotropy and cooling rate are usually expected for bricks than for hearths, domestic ovens, production kilns or burnt dwelling remains (there are no results from pottery in the Bulgarian dataset) and both factors are not evaluated for most of the older results. All this can explain the contradictions observed between some of the experimental results juxtaposed over the absolute time scale. In an attempt to clarify these contradictions 13 baked clay structures from eight archaeological sites were archaeomagnetically studied producing seven new directional and eight new intensity data. The samples collected possess variable magnetic properties suggesting differences in clay sources and/or firing conditions. Magnetically soft minerals prevail in seven structures but in the remaining six, abundant HCSLT phase is detected. The success rate of archaeointensity determination experiments vary from 49 to 100 %. It appears that samples containing HCSLT phase always produces good araeointensity results unlike those with the dominant presence of soft carriers.</p><p>The new reference points are compared with the present compilation of Bulgarian archaeomagnetic dataset and with the data from the neighboring countries.</p><p> </p><p>This study is supported by the grant KP-06-Russia-10 from the Bulgarian National Science Fund and Russian Foundation of the Basic Research grant 19-55-18006.</p>


Ocean Science ◽  
2012 ◽  
Vol 8 (4) ◽  
pp. 473-483 ◽  
Author(s):  
J. Karvonen

Abstract. An algorithm for computing ice drift from pairs of synthetic aperture radar (SAR) images covering a common area has been developed at FMI. The algorithm has been developed based on the C-band SAR data over the Baltic Sea. It is based on phase correlation in two scales (coarse and fine) with some additional constraints. The algorithm has been running operationally in the Baltic Sea from the beginning of 2011, using Radarsat-1 ScanSAR wide mode and Envisat ASAR wide swath mode data. The resulting ice drift fields are publicly available as part of the MyOcean EC project. The SAR-based ice drift vectors have been compared to the drift vectors from drifter buoys in the Baltic Sea during the first operational season, and also these validation results are shown in this paper. Also some navigationally useful sea ice quantities, which can be derived from ice drift vector fields, are presented.


2016 ◽  
Author(s):  
H. Dietze ◽  
U. Löptien

Abstract. Deoxygenation in the Baltic Sea endangers fish yields and favours noxious algal blooms. Yet, vertical transport processes ventilating the oxygen-deprived waters at depth and replenishing nutrient-deprived surface waters (thereby fuelling export of organic matter to depth), are not comprehensively understood. Here, we investigate the effects of the interaction between surface currents and winds (also referred to as eddy/wind effects) on upwelling in an eddy-rich general ocean circulation model of the Baltic Sea. Contrary to expectations we find that accounting for current/wind effects does inhibit the overall vertical exchange between oxygenated surface waters and oxygen-deprived water at depth. At major upwelling sites, however, as e.g. off the south coast of Sweden and Finland, the reverse holds: the interaction between topographically steered surface currents with winds blowing over the sea results in a climatological sea surface temperature cooling of 0.5 K. This implies that current/wind effects drive substantial local upwelling of cold and nutrient-replete waters.


2002 ◽  
Vol 12 (4) ◽  
Author(s):  
K. G. Omelyanov ◽  
A. A. Sapozhenko

AbstractA set A of integers is called sum-free if a + b ∉ A for any a, b ∈ A. For an arbitrary Ɛ > 0, let ssThis research was supported by the Russian Foundation for Basic Research, grant 01-01-00266.


2007 ◽  
Vol 24 (9) ◽  
pp. 1655-1664 ◽  
Author(s):  
Jenny A. U. Nilsson ◽  
Peter Sigray ◽  
Robert H. Tyler

Abstract The possibility of using data from a cable-based observational system for long-term monitoring of barotropic flow in the Baltic Sea was investigated. Measurements were made of the induced potential differences between Visby on the island of Gotland and Västervik on the Swedish mainland and a yearlong period was studied in order to ensure the presence of seasonal fluctuations. The predictions from a 2D electric-potential model, forced by velocity fields from a shallow-water circulation model, proved to be well correlated with the observations. A winter and a summer period were selected for a thorough analysis, the results of which indicated a stronger correlation during winter. This implies that the relative importance of the barotropic forcing tends to weaken during summer. The spatial coverage of the induced potential differences for the cable region was found to encompass a considerable part of the Baltic proper. The correlation study indicated that the winter circulation in the Baltic proper showed “broad-scale” motion, whereas summer conditions were characterized by a barotropic gyre. An overall result of the investigation is that geoelectric monitoring is capable of providing useful data for oceanographic purposes.


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