Multi-sensor in situ observations to resolve the sub-mesoscale features in the stratified Gulf of Finland, Baltic Sea
High-resolution numerical modeling, remote sensing, and in situ data have revealed significant role of sub-mesoscale features in shaping the distribution pattern of tracers in the ocean's upper layer. However, in situ measurements are difficult to conduct with the required resolution and covera...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-05-01
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| Series: | Ocean Science |
| Online Access: | http://www.ocean-sci.net/12/715/2016/os-12-715-2016.pdf |
| Summary: | High-resolution numerical modeling, remote sensing, and in
situ data have revealed significant role of sub-mesoscale features in shaping
the distribution pattern of tracers in the ocean's upper layer. However, in
situ measurements are difficult to conduct with the required resolution and
coverage in time and space to resolve the sub-mesoscale, especially in such
relatively shallow basins as the Gulf of Finland, where the typical baroclinic
Rossby radius is 2–5 km. To map the multi-scale spatiotemporal variability
in the gulf, we initiated continuous measurements with autonomous devices,
including a moored profiler and Ferrybox system, which were complemented by
dedicated research-vessel-based surveys. The analysis of collected
high-resolution data in the summers of 2009–2012 revealed pronounced variability at
the sub-mesoscale in the presence of mesoscale upwelling/downwelling, fronts,
and eddies. The horizontal wavenumber spectra of temperature variance in the
surface layer had slopes close to −2 between the lateral scales from 10 to
0.5 km. Similar tendency towards the −2 slopes of horizontal wavenumber
spectra of temperature variance was found in the seasonal thermocline between
the lateral scales from 10 to 1 km. It suggests that the ageostrophic
sub-mesoscale processes could contribute considerably to the energy cascade
in such a stratified sea basin. We showed that the intrusions of water with
different salinity, which indicate the occurrence of a layered flow structure,
could appear in the process of upwelling/downwelling development and
relaxation in response to variable wind forcing. We suggest that the
sub-mesoscale processes play a major role in feeding surface blooms in the
conditions of coupled coastal upwelling and downwelling events in the Gulf of
Finland. |
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| ISSN: | 1812-0784 1812-0792 |