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Kjell Arne Mork and Henrik Søiland

The deep circulation in the Norwegian Sea from subsurface drifters. Kjell Arne Mork and Henrik Søiland Institute of Marine Research and Bjerknes Centre for Climate Research, Norway. 15 Years of progress in radar altimetry Argo workshop, Venice 2006.

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Kjell Arne Mork and Henrik Søiland

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  1. The deep circulation in the Norwegian Sea from subsurface drifters Kjell Arne Mork and Henrik Søiland Institute of Marine Research and Bjerknes Centre for Climate Research, Norway 15 Years of progress in radar altimetry Argo workshop, Venice 2006 15 Years of progress in radar altimetry, Venice 2006

  2. Surface circulation in the Nordic Seas (Greenland, Norwegian and Iceland Sea) 3000 NORWEGIAN SEA 3000 Atlantic water Surface circulation in the North Atlantic Coastal water Arctic water 15 Years of progress in radar altimetry, Venice 2006

  3. The deep/bottom circulation in the Nordic Seasbefore the Argo floats • Models of the deep circulation: • The time-mean circulation is along f/H contours (Nøst and Isachsen, 2003; Eldevik et al., 2005) Red vectors are observations • Few observations of the deep ocean circulation in the Nordic Seas until Argo floats were deployed From Nøst and Isachsen (2003) 15 Years of progress in radar altimetry, Venice 2006

  4. June 2002 August 2003 Institute of Marine Research (Norway) has deployed nine Argo floats that drift at 1500 m depth The parking depth at 1500 m was chosen due to the topography and the low stratification in the deep water 2000 3000 15 Years of progress in radar altimetry, Venice 2006

  5. Drift, temperature and salinity from one Argo float : 10 days : Deployment : Last position Temp. June 2002 – October 2005 3 1 0 -0.5 -0.7 3000 Jan03 Jan04 Jan05 Sal. 1000 35 35 34.9 34.9 Bottom depth: contour interval is 500 m 15 Years of progress in radar altimetry, Venice 2006

  6. : 10 days : Deployment : Last position 9 Argo float trajectories, 2002/2003-2006 In total: 960 profiles Bottom depth: contour interval is 500 m 1000 15 Years of progress in radar altimetry, Venice 2006

  7. : speed less than 10 cm/s : speed larger than 10 cm/s Circulation at 1500 m depth from the Argo floats 1000 Bottom depth contour interval: 500 m 15 Years of progress in radar altimetry, Venice 2006

  8. June 2002 – April 2005 : first pass : second pass TOPOGRAPHIC STEERING 3000 2000 3000 Bottom depth: contour interval is 500 m 15 Years of progress in radar altimetry, Venice 2006

  9. : first pass : second pass TOPOGRAPHIC STEERING - 2 June 2002 – May 2005 3000 2500 3000 Bottom depth: contour interval is 500 m 15 Years of progress in radar altimetry, Venice 2006

  10. : speed less than 10 cm/s : speed larger than 10 cm/s Circulation at 1500 m depth from the Argo floats Seasonal variation? 1000 Bottom depth contour interval: 500 m 15 Years of progress in radar altimetry, Venice 2006

  11. Seasonal variation in the speed Maximum in March-April 7±1.5 cm/s Maximum in Apr-Jun 3.5±0.5 cm/s 15 Years of progress in radar altimetry, Venice 2006

  12. Seasonal variation in the speed Maximum in March-April 7±1.5 cm/s Atmospheric forcing? Maximum in Apr-Jun 3.5±0.5 cm/s 15 Years of progress in radar altimetry, Venice 2006

  13. Spring Winter Seasonal anomalous bottom currents (relative to annual mean) Summer Autumn Calculated by combining altimetry and hydrography Mork and Skagseth (2005) 15 Years of progress in radar altimetry, Venice 2006

  14. Spring Comparing the changes in the circulation with the integrated wind stress curl over the area (within a closed H-contour) Autumn wind change in speed Jan Mar May Sep Nov 15 Years of progress in radar altimetry, Venice 2006 Mork and Skagseth (2005)

  15. Change in speed from Argo floats Spring Autumn wind change in speed Jan Mar May Sep Nov 15 Years of progress in radar altimetry, Venice 2006

  16. Summary • The deep circulation in the Norwegian Sea is cyclonic and there are strong topographic steering. • The annual speed is 3.5 cm/s and 7 cm/s in the Norwegian and Lofoten Basin, respectively. • Seasonal variation in the speed: ±1.5 cm/s in the Lofoten Basin ±0.5 cm/s in the Norwegian Basin • Wind forced seasonal variation? Wind stress curl in phase with the change of speed in the Lofoten Basin. 15 Years of progress in radar altimetry, Venice 2006

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