workshop deep ocean exchange with the shelf cape town, 6-8 october 2008 the role of deep eddies in...
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WORKSHOPWORKSHOP
Deep Ocean Exchange with the ShelfDeep Ocean Exchange with the Shelf Cape Town, 6-8 October 2008Cape Town, 6-8 October 2008
The role of deep eddies in offshore The role of deep eddies in offshore transferstransfers
Isabel Ambar and Nuno SerraIsabel Ambar and Nuno Serra
Instituto de OceanografiaInstituto de Oceanografia
Faculdade de Ciências, Universidade de LisboaFaculdade de Ciências, Universidade de Lisboa
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Chlorophyll pigments(11 July 2002)
SST(11 July 2002)
Surface filaments and eddies are known as key factors in the transfer processes of mass, heat and momentum between shelf and deep ocean regions.
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Do sub-surface eddies, like those detaching from the Mediterranean Undercurrent off Iberia – the meddies - play a role in the transfers from shelf to deep ocean ?
Richardson, 2000
Question
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Meddies are Mediterranean Water lens-like coherent structures, existing at depths from 600 to 1400 m, in solid body anticyclonic rotation, with typical diameters of about 50 – 100 km.
50 – 100 km
800 m
600 m
1400 m
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Floats launched during MEDTOP
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Eddy generation at Estremadura Promontory(23 April 2001 - 18 April 2002)
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AMUSE meddies
(1993-1995)
CANIGO meddies
(1997-1999)
MEDTOP meddies
(2001-2003)
float depths:
500 m
800 m
1200 m
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In the last decade, field observations off the southern coast of Iberia were able to detect the presence of cyclones associated with meddies to form vortex pairs - dipoles dipoles - at the level of the Mediterranean Water.
Serra and Ambar (2002)
dipoleGeneration at the Portimão Canyon region
dipole
Generation at Cape St. VincentSerra et al. (2002)
meddy
cyclone
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These cyclones play a role on the detachment of the meddies from the Mediterranean Undercurrent and seem to be fundamental for the translation of meddies away from their generation zone.
Cape St Vincent promotes the overshoot and separation of the MW Undercurrent
Advection or anticyclone-cyclone coupling provides detachment
Serra, Ambar and Käse (2005)
Eddy generation at Cape St. Vincent
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Eddy generation at the Portimão Canyon region
Stretching of the MW layer at the Portimao Canyon induces cyclonic vorticity
Serra, Ambar and Käse (2005)Cyclone extracts MW from the slope -> dipole ejection
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The dynamical fields associated with the meddies and cyclones extend vertically much farther than the depth range where the thermohaline anomaly is detected, and may reach levels down to 3000 m or up to the sea surface.
Oliveira, Serra, Ambar & Fiúza (2000)
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Dipole followed by remote sensing (sea surface temperature) and by RAFOS
25 May 2001 18 June 2001
MEDTOP project
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SST
12 Jun 98 – 14 Sep 9812 Jun 98 – 14 Sep 98
Data received and processed at IOFCUL
Chlorophyll pigments concentration
17 Jun 9817 Jun 98
Serra, Boutov and Ambar (to be submitted)
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Vertical structure of the model dipoles
Salinity + velocity normal to the section
AnticyclonesCyclones
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model SST (°C) model MW thickness (m)
Serra, 2008
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surface temperature and velocity salinity and velocity at 1200 m
Serra, 2008
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Model SST In situ Chl-a
Serra, 2008
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SST
1 Apr 01 – 5 Aug 011 Apr 01 – 5 Aug 01 6 Jun 016 Jun 01
Serra, Boutov and Ambar (to be submitted)
Chlorophyll pigments concentration
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Deep-Sea Research II 52 (2005) 383–408Observations and numerical modelling of the Mediterraneanoutflow splitting and eddy generationNuno Serra, Isabel Ambar, Rolf Kaese
Journal of Marine Systems 71 (2008) 195–220Observations of the Mediterranean Undercurrent and eddiesin the Gulf of Cadiz during 2001I. Ambar, N. Serra, F. Neves, T. Ferreira