CR 48:73-84 (2011)  -  DOI: https://doi.org/10.3354/cr01032

The development of seasonal structural fronts in the Baltic Sea after winters of varying severity

Natalia Demchenko1,*, Irina Chubarenko1, Seppo Kaitala2

1P.P.Shirshov Institute of Oceanology of Russian Academy of Sciences, Atlantic branch, Prospect Mira 1, 236022 Kaliningrad, Russia
2Finnish Environment Institute (SYKE), Mechelininkatu 34a, PO BOX 140, 00251 Helsinki, Finland

ABSTRACT: The manifestation in the Baltic Sea of a seasonal, structural, thermally-induced front (a direct analogue of the lacustrine thermal bar) and its specific features after winters of different severity are examined. Analysis of long-term, spring-period, monthly mean SST data reveals that surface water temperatures first exceed the (salinity-dependent) temperature of maximum density (Tmd) in the southern part of the Baltic Sea. This phenomenon advances northwards at a speed of about 11 to 16 km d–1, traversing the breadth of the sea within 8 to 10 wk. Surface temperature measurements across the Tmd-isotherm demonstrate that after the severe winter of 2002-2003 the frontal zone was highly pronounced, with a horizontal temperature gradient 10 to 100 times as large as the long-term monthly mean equivalent. Although the horizontal gradient was smaller after the mild winter of 2006-2007, it was still 10 times as large as the long-term monthly mean gradient. A clear correlation of thermal front advancement with biological parameters is revealed: an area of elevated chlorophyll a (about 200 km in width) associated with the Tmd was observed after severe winters, with the characteristic life-time of this zone 1 mo longer than that occurring after mild winters.


KEY WORDS: Temperature of maximum density · Thermal bar · Mixing · Baltic Sea


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Cite this article as: Demchenko N, Chubarenko I, Kaitala S (2011) The development of seasonal structural fronts in the Baltic Sea after winters of varying severity. Clim Res 48:73-84. https://doi.org/10.3354/cr01032

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