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| Titel |
Friction and mixing effects on potential vorticity for bottom current crossing a marine strait: an application to the Sicily Channel (central Mediterranean Sea) |
| VerfasserIn |
F. Falcini, E. Salusti |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1812-0784
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| Digitales Dokument |
URL |
| Erschienen |
In: Ocean Science ; 11, no. 3 ; Nr. 11, no. 3 (2015-05-21), S.391-403 |
| Datensatznummer |
250117224
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| Publikation (Nr.) |
 copernicus.org/os-11-391-2015.pdf |
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| Zusammenfassung |
We discuss here the evolution of vorticity and potential vorticity (PV) for
a bottom current crossing a marine channel in shallow-water approximation,
focusing on the effect of friction and mixing. The purpose of this research
is indeed to investigate the role of friction and vertical entrainment on
vorticity and PV spatial evolution in channels or straits when along-channel
morphology variations are significant. To pursue this investigation, we pose
the vorticity and PV equations for a homogeneous bottom water vein and we
calculate these two quantities as an integral form. Our theoretical findings
are considered in the context of in situ hydrographic data related to the
Eastern Mediterranean Deep Water (EMDW), i.e., a dense, bottom water vein that
flows northwestward, along the Sicily Channel (Mediterranean Sea). Indeed,
the narrow sill of this channel implies that friction and entrainment need
to be considered. Small tidal effects in the Sicily Channel allow for a
steady theoretical approach.
We argue that bottom current vorticity is prone to significant sign changes
and oscillations due to topographic effects when, in particular, the current
flows over the sill of a channel. These vorticity variations are, however,
modulated by frictional effects due to seafloor roughness and morphology.
Such behavior is also reflected in the PV spatial evolution, which shows an
abrupt peak around the sill region. Our diagnoses on vorticity and PV allow
us to obtain general insights about the effect of mixing and friction on the
pathway and internal structure of bottom-trapped currents flowing through
channels and straits, and to discuss spatial variability of the frictional
coefficient. Our approach significantly differs from other PV-constant
approaches previously used in studying the dynamics of bottom currents
flowing through rotating channels. |
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