Upwelling characteristics in the Gulf of Finland (Baltic Sea) as revealed by Ferrybox measurements in 2007–2013
Ferrybox measurements have been carried out between Tallinn and Helsinki in the Gulf of Finland (Baltic Sea) on a regular basis since 1997. The system measures autonomously water temperature, salinity, chlorophyll <i>a</i> fluorescence and turbidity and takes water samples for further an...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-07-01
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| Series: | Ocean Science |
| Online Access: | http://www.ocean-sci.net/12/843/2016/os-12-843-2016.pdf |
| Summary: | Ferrybox measurements have been carried out between Tallinn and Helsinki in
the Gulf of Finland (Baltic Sea) on a regular basis since 1997. The system
measures autonomously water temperature, salinity, chlorophyll <i>a</i>
fluorescence and turbidity and takes water samples for further analyses at a
predefined time interval. We aimed to show how the Ferrybox technology could
be used to study the coastal upwelling events in the Gulf of Finland. Based
on the introduced upwelling index and related criteria, 33 coastal upwelling
events were identified in May–September 2007–2013. The number of events, as
well as the frequency of their occurrence and intensity expressed as a sum of
daily average temperature deviations in the 20 km wide coastal area, were
almost equal near the northern and southern coasts. Nevertheless, the wind
impulse, which was needed to generate upwelling events of similar intensity,
differed between the northern and southern coastal areas. It is suggested
that the general thermohaline structure adapted to the prevailing forcing and
the estuarine character of the basin weaken the upwelling created by the
westerly to southwesterly (up-estuary) winds and strengthen the upwelling
created by the easterly to northeasterly (down-estuary) winds. Two types of
upwelling events were identified – one characterized by a strong temperature
front and the other revealing gradual decrease in temperature from the open
sea to the coastal area, with maximum temperature deviation close to the
shore. |
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| ISSN: | 1812-0784 1812-0792 |