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Pathways of Atlantic Water

Pathways of Atlantic Water. Cecilie Mauritzen – Norwegian Meteorological Institute. NOClim 2 Workshop, M/S Nordkapp, October 1 2003. Meridional overturning circulation. Water sinks. But this is not where it get dense. 60N. EQ. Greenland-Scotland Ridge. Entrainment. 6Sv. Dense, but

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Pathways of Atlantic Water

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  1. Pathways of Atlantic Water Cecilie Mauritzen – Norwegian Meteorological Institute NOClim 2 Workshop, M/S Nordkapp, October 1 2003

  2. Meridional overturning circulation Water sinks. But this is not where it get dense 60N EQ

  3. Greenland-Scotland Ridge Entrainment 6Sv Dense, but still shallow Sinking 700m 6Sv 3000 m 60N Nordic Seas

  4. Erika Dan 1962, 59oN Northward bound warm water Velocity cores (”branches”) ≠ distribution of warm water Southward bound cold water Schematic

  5. Faroe-Shetland Channel: Dense water fills 600m; AIW, NSDW Warm water on slope 8-9 degrees in core

  6. Svinøy (example from 1988) Summer Winter 7-8 degrees in core

  7. Gimsøy (winter 1988) 6-7 degrees in core

  8. Grand Banks In a budget: account for transports and air sea fluxes Cooling and significant freshening Rockall Lofoten basin Enough water (7 Sv) is transformed to the right density range Fram Strait Magical boundary Eurasian Basin Overflows (wide range)

  9. Transformation in the warm Atlantic Current does not involve deep mixed layers. So whats up with the deep mixed layer sites, the Greenland and Iceland Seas? • Attempts to quantify export of dense water from open-ocean deep convection sites result in small numbers (< 1 Sv). The tracer release experiment in the Greenland Sea (TRACTOR) showed qualitatively the same thing; it took for example two years before any dense water reached the overflows. I.e. not a BIG player. • BUT: is it possible that there has been times when significant amounts of the Atlantic Water did take a shortcut through the Iceland or Greenland Seas? • Schematic

  10. Air-Sea Heat Exchange Air-sea heat fluxes not any larger in the Iceland and Greenland Seas than in the rest of the Nordic Seas

  11. Hydrographic Conditions in the Iceland Sea

  12. Irminger Current 1992?

  13. Conclusions • Establishment of pathways requires quantification • Get the most important players (say, 4 out of 5 Sverdrup) • There has been very significant hydrographic changes in the Nordic Seas in the 20th century – need to establish whether the pathways may have changed, just as we need to establish whether the strength has changed. • Stay tuned……slow detective work (and, getting access to the most useful data isn’t always so easy)

  14. Moving into the Nordic Seas… • Roughly 7 Sv warm water in • Roughly 1 Sv cold water in • Roughly 3 Sv cold, light water out • Roughly 5 Sv cold, dense water out

  15. Typiske snitt – hvordan komme fram til sirkulasjonsbilde

  16. Evolution of warm Atlantic Water:Cooling AND freshening!

  17. Svinøy section Orvik and Skagseth 2002 Time series is short, but suggest time variability in volume flux of warm inflow water

  18. Gimsøy

  19. Schematic of the MOC How do we determine the pathways of water masses?

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