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

Norwegian Meteorological InstituteM/S Nordkapp Fall 2003 Meridional overturning circulation EQ 60N Water sinks. But this is not where it get dense

Norwegian Meteorological InstituteM/S Nordkapp Fall 2003 Greenland-Scotland Ridge 60N 700m 3000 m Sinking Entrainment Nordic Seas Dense, but still shallow 6Sv

Norwegian Meteorological InstituteM/S Nordkapp Fall 2003 Erika Dan 1962,  o  Northward bound warm water Southward bound cold water Velocity cores (”branches”) ≠ distribution of warm water Schematic

Norwegian Meteorological InstituteM/S Nordkapp Fall degrees in core Faroe-Shetland Channel: Dense water fills 600m; AIW, NSDW Warm water on slope

Norwegian Meteorological InstituteM/S Nordkapp Fall degrees in core SummerWinter Svinøy (example from 1988)

Norwegian Meteorological InstituteM/S Nordkapp Fall 2003 Gimsøy (winter 1988) 6-7 degrees in core

Norwegian Meteorological InstituteM/S Nordkapp Fall 2003 Grand Banks Rockall Lofoten basin Fram Strait Eurasian Basin Overflows (wide range) In a budget: account for transports and air sea fluxes Cooling and significant freshening Magical boundary Enough water (7 Sv) is transformed to the right density range

Norwegian Meteorological InstituteM/S Nordkapp Fall 2003 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

Norwegian Meteorological InstituteM/S Nordkapp Fall 2003 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

Norwegian Meteorological InstituteM/S Nordkapp Fall 2003 Hydrographic Conditions in the Iceland Sea

Norwegian Meteorological InstituteM/S Nordkapp Fall 2003

Norwegian Meteorological InstituteM/S Nordkapp Fall 2003 Irminger Current 1992?

Norwegian Meteorological InstituteM/S Nordkapp Fall 2003 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)

Norwegian Meteorological InstituteM/S Nordkapp Fall 2003

Norwegian Meteorological InstituteM/S Nordkapp Fall 2003 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

Norwegian Meteorological InstituteM/S Nordkapp Fall 2003 Typiske snitt – hvordan komme fram til sirkulasjonsbilde

Norwegian Meteorological InstituteM/S Nordkapp Fall 2003

Norwegian Meteorological InstituteM/S Nordkapp Fall 2003 Evolution of warm Atlantic Water: Cooling AND freshening ! TemperatureSalinity Grand Banks Rockall835.3 Norskehavsbassenget Lofoten/Barents Sea Arctic Ocean Entrance335 Arctic Ocean

Norwegian Meteorological InstituteM/S Nordkapp Fall 2003

Norwegian Meteorological InstituteM/S Nordkapp Fall 2003

Norwegian Meteorological InstituteM/S Nordkapp Fall 2003

Norwegian Meteorological InstituteM/S Nordkapp Fall 2003 Svinøy section Orvik and Skagseth 2002 Time series is short, but suggest time variability in volume flux of warm inflow water

Norwegian Meteorological InstituteM/S Nordkapp Fall 2003

Norwegian Meteorological InstituteM/S Nordkapp Fall 2003 Gimsøy

Norwegian Meteorological InstituteM/S Nordkapp Fall 2003 Schematic of the MOC How do we determine the pathways of water masses?