Scientia Marina, Vol 80, No S1 (2016)

Interaction of Mediterranean Water lenses with Antarctic Intermediate Water off Northwest Africa

Francisco José Electronica Machín
Department of Physics, University of Las Palmas de Gran Canaria, Spain

Josep L. Pelegrí
Institut de Ciències del Mar, CSIC, Spain


Mediterranean Water lenses (meddies) in the eastern North Atlantic, north of the Canary Islands, appear to often have their salty and nutrient-poor core accompanied by relatively fresh and nutrient-rich waters on top. We describe several occurrences of freshwater halos and berets for meddies sampled north of the Canary Islands—with instrumented moorings, Argo floats and oceanographic cruises—and identify the source of these fresh anomalies as diluted Antarctic Intermediate Water (AAIW). We propose that this capping takes place off Northwest Africa, as the southward-advected meddy interacts with the northward-advected AAIW. This interpretation is consistent with a simple analysis of the relevant advective-diffusive time scales associated with the passage of meddies under a layer of AAIW, and suggests that meddies may be a mechanism for AAIW export far into the North Atlantic Ocean.


meddies; Antarctic Intermediate Water; eastern North Atlantic

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Armi L., Hebert D., Oakey N., et al. 1988. The history and decay of a Mediterranean salt lens. Nature 333: 649-651.

Armi L., Hebert D., Oakey N., et al. 1989. Two years in the life of a Mediterranean salt lens. J. Phys. Oceanogr. 19: 354-383.<0354:TYITLO>2.0.CO;2

Bashmachnikov I., Carton X. 2012. Surface signature of Mediterranean water eddies in the northeastern atlantic: effect of the upper ocean stratification. Ocean Sci. 8(6): 931-943.

Batchelor G. 1977. An Introduction to Fluid Dynamics, Cambridge Univ. Press. PMCid:PMC1667992

Biescas B., Sallarès V., Pelegrí J.L., et al. 2008. Imaging meddy finestructure using multichannel seismic reflection data. Geophys. Res. Lett. 35: L11609.

Bower A., Armi L., Ambar I. 1997. Lagrangian observations of meddy formation during a Mediterranean underwater seeding experiment. J. Phys. Oceanogr. 27: 2545-2575.<2545:LOOMFD>2.0.CO;2

Hedstrom K., Armi L. 1988. An experimental study of homogeneous lenses in a stratified rotating fluid. J. Fluid Mechanics 191: 535-556.

Jackett D., McDougall T. 1997. A neutral density variable for the world's oceans. J. Phys. Oceanogr. 27: 237-263.<0237:ANDVFT>2.0.CO;2

Law C., Martin A., Liddicoat M., et al. 2001. A Lagrangian sf 6 tracer study of an anticyclonic eddy in the North Atlantic: patch evolution, vertical mixing and nutrient supply to the mixed layer. Deep-Sea Res. II 48(4): 705-724.

Ledwell J., Watson A., Law C. 1998. Mixing of a tracer in the pycnocline, J. Geophys. Res. 103(C10): 21499-21529.

Louarn E., Morin P. 2011. Antarctic intermediate water influence on Mediterranean Sea water outflow, Deep-Sea Res. I 58(9): 932-942.

Lutjeharms J.R.E., Shillington F.A., Duncombe-Rae C.M. 1991. Observations of extreme upwelling filaments in the Southeast Atlantic Ocean. Science 253: 774-776. PMid:17835495

Machín F., Hernández-Guerra A., Pelegrí J.L. 2006. Mass fluxes in the Canary Basin. Prog. Oceanog. 70(2-4): 416-447.

Machín F., Pelegrí J.L. 2009. Northward penetration of Antarctic Intermediate Water off Northwest Africa. J. Phys. Oceanogr. 39(3): 512-535.

Machín F., Pelegrí J.L., Fraile-Nuez E., et al. 2010. Seasonal flow reversals of intermediate waters in the canary current system east of the Canary Islands. J. Phys. Oceanogr. 40(8): 1902-1909.

McDowell S.E., Rossby H.T. 1978. Mediterranean water: An intense mesoscale eddy off the Bahamas. Science 202: 1085-1087. PMid:17777959

Nof D. 1988. The propagation of 'streamers' along the periphery of warm-core rings. Deep-Sea Res. 35: 1483-1498.

Parrilla G., Neuer S., Le Traon P.-Y., et al. 2002. Topical studies in oceanography: Canary Islands Azores Gibraltar Observations (CANIGO). Volume 1: Studies in the northern Canary Islands basin. Deep-Sea Res. II 49: 3409-3413.

Pastor M., Pe-a-Izquierdo J., Pelegrí J.L., et al. 2012. Meridional changes in water mass distributions off NW Africa during November 2007/2008. Cienc. Mar. 38(1B): 223-244.

Pedlosky J. 1979. Geophysical Fluid Dynamics. Springer-Verlag. New York.

Richardson P., Bower A., Zenk W. 2000. A census of Meddies tracked by floats. Prog. Oceanog. 45: 209-250.

Ryan J.P., Yoder J.A., Townsend D.W. 2001. Influence of a Gulf Stream warm-core ring on water mass and chlorophyll distributions along the southern flank of Georges Bank. Deep-Sea Res. II 48: 159-178.

Siedler G., Armi L., Müller T.J. 2005. Meddies and decadal changes at the Azores Front from 1980 to 2000. Deep-Sea Res. II 52(3- 4): 583-604.

Tsuchiya M., Talley L., McCartney M. 1992. An eastern Atlantic section from Iceland southward across the Equator. Deep-Sea Res. 39(11/12A): 1885-1917.

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