Very high-resolution modelling of submesoscale turbulent patterns and processes in the Baltic Sea
<p>In order to simulate submesoscale turbulent patterns and processes (STPPs) and to analyse their properties and dynamics, the Regional Ocean Modeling System (ROMS) was run for June 2016 in a subregion of the Baltic Sea. To create a realistic mesoscale environment, ROMS with 500&thins...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-05-01
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| Series: | Ocean Science |
| Online Access: | https://www.ocean-sci.net/16/657/2020/os-16-657-2020.pdf |
| Summary: | <p>In order to simulate submesoscale turbulent patterns and processes
(STPPs) and to analyse their properties and dynamics, the Regional
Ocean Modeling System (ROMS) was run for June 2016 in a subregion of
the Baltic Sea. To create a realistic mesoscale environment, ROMS with
500 m horizontal resolution (referred to as R500) is one-way nested
into an existing operational model, and STPPs with horizontal scales
< 1 km are resolved with a second nest of 100 m resolution
(R100). Both nests use 10 terrain-following layers in the vertical.
The comparison of the R500 results with a satellite image shows fair
agreement. While R500 is driven by realistic air–sea fluxes, the
atmospheric forcing is turned off in R100 because it prevents the
generation of STPPs and blurs submesoscale structures. Therefore, R100
provides deep insight into ageostrophic processes and associated
quantities under quasi-adiabatic conditions that are approximately met
in no-wind or light-wind situations. The validity of the results is
furthermore limited to the selected region and the time of the year.
STPPs evolve rapidly within a about a day. They are characterized by
vertical speeds of 𝒪(10) m d<sup>−1</sup> and relative vorticities
and divergences reaching multiples of the Coriolis parameter. Typical
elements of the secondary circulation of two-dimensional
strain-induced frontogenesis are identified at an exemplary front in
shallow water, and details of the ageostrophic flow field are
revealed. The conditions for inertial and symmetric instability are
evaluated for the whole domain, and the components of the tendency
equation are computed in a subregion. While anticyclonic eddies are
generated solely along coasts, cyclonic eddies are rolled-up streamers
and found in the entire domain. A special feature of the cyclones is
their ability to absorb internal waves and to sustain patches of
continuous upwelling for several days, favouring plankton growth. The
kinematic properties show good agreement with observations, while some
observed details within a small cyclonic eddy are only partly
reproduced, most likely due to a lack of horizontal resolution or
nonhydrostatic effects.</p> |
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| ISSN: | 1812-0784 1812-0792 |