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Ocean Dynamics

, Volume 61, Issue 1, pp 51–68 | Cite as

Modification by lateral mixing of the Warm Deep Water entering the Weddell Sea in the Maud Rise region

  • Harry Leach
  • Volker Strass
  • Boris Cisewski
Article

Abstract

Deep water originating in the North Atlantic is transported across the Antarctic Circumpolar Current by eddies and, after circumnavigating of the Antarctic, enters the Weddell Gyre south of Africa. As it does so, it rises up from mid-depth towards the surface. The separate temperature and salinity maxima, the Upper and Lower Circumpolar Deep Waters, converge to form the Warm Deep Water. Cores of this water mass on the southern flank of the eastern Weddell Gyre show a change in characteristic as they flow westward in the Lazarev Sea. Observations have been made along four meridional sections at 3° E, 0°, 3° W and 6° W between 60 and 70° S during the Polarstern Cruise ANTXXIII/2 in 2005/2006. These show that a heterogeneous series of warm and salty cores entering the region from the east both north and south of Maud Rise (65° S, 3° W) gradually merge and become more homogeneous towards the west. The gradual reduction in the variance of potential temperature on isopycnals is indicative of isopycnic mixing processes. A multiple regression technique allows diagnosis of the eddy diffusivities and, thus, the relative importance of isopycnic and diapycnic mixing. The method shows that the isopycnic diffusivity lies in the range 70–140 m2 s−1 and the diapycnic diffusivity reaches about 3 × 10−6 m2 s−1. Scale analysis suggests that isopycnic diffusion dominates over diapycnic diffusion in the erosion of the Warm Deep Water cores.

Keywords

Weddell Gyre Lazarev Sea Maud Rise Warm Deep Water Mixing 

Notes

Acknowledgements

We gratefully acknowledge the help and support of the captain and crew of Polarstern and our fellow scientists on board. HL’s participation in the cruise was supported by a travel grant from the Royal Society. The Bundesministerium für Bildung und Forschung LAKRIS programme provided salary and travel for BC in a project led by Prof. M. Rhein at the Institute for Environmental Physics at the University of Bremen (Grant Reference LAKRIS 03F0400B).

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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  1. 1.Department of Earth and Ocean SciencesUniversity of LiverpoolLiverpoolUK
  2. 2.Alfred-Wegener-Institut für Polar- und MeeresforschungBremerhavenGermany
  3. 3.Institut für UmweltphysikUniversität BremenBremerhavenGermany

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