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Kjell Arne Mork and Øystein Skagseth Institute of Marine Research, Norway

Hydrographic variability in the Norwegian Sea during 1995-2010 Heat content in the Norwegian Sea during 1995-2010. Kjell Arne Mork and Øystein Skagseth Institute of Marine Research, Norway. The Norwegian Sea. Norwegian Sea. Main surface currents in the Nordic Seas.

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Kjell Arne Mork and Øystein Skagseth Institute of Marine Research, Norway

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  1. Hydrographic variability in theNorwegianSea during 1995-2010Heat content in theNorwegianSea during 1995-2010 Kjell Arne Mork and Øystein Skagseth Institute of Marine Research, Norway

  2. The NorwegianSea NorwegianSea Main surfacecurrents in the Nordic Seas SST from NODC (4km), Kilpatrick et al., 2001

  3. Hydrographic data • ICES and Argo data • From April 15th – June 15th, 1995-2010. A period with international coordinated cruises (WPGNAPES). • Data control (range check, density stability, etc.) • Seasonal correction of temperature using World Ocean Atlas 2009 (WOA09) • Gridding: statisticalinterpolation (objectiveanalysis) usingbackgroundfield (all obs.+WOA09)

  4. Data coveragevarieswithyear 1998 2001 All years: 1995-2010

  5. Heat content Integratetemperature, relative to a referencetemperature (Tref), from theseasurface to a referencesurface (z=-h), seasurface • h = constant (500 m): Ocean Heat Content (OHC) • h = thedepth of thedensitysurface (st=27.9); h = h (x,y,t): Relative Heat Content (RHC) T(z) z = -h, T=Tref 2) willreducetheeffect of eddies and internalwaves (e.g. Bindoff and McDougall, 1994; Palmer and Haines, 2009)

  6. Time-averageddepth of thedensitysurface (st=27.9) and temperature at thedensitysurface Depth Temperature (Tref) Warmest water in thenorthbecause of downwardmixing in thenorth (Rossby et al., 2009)

  7. Relative Heat Content (RHC) anomaly Jm-2 1995-2002 2003-2010

  8. 2003-2010 Heat contentanomaly (J m-2) 1995-2002 1.5x109 RHC : 0 – h (st=27.9) 0 -1.5x109 OHC : 0 - 500 m

  9. 1995-2010: a warmingperiod Temperatureanomaly in theSvinøy-NV and Gimsøy-NVsection. Data are 5 yearsmovingaverages Increase in temperature and salinity due to SPG changes (Hatun et al., 2005; Holliday et al., 2008)

  10. Divideintotwo areas: North and South • North: Lofoten Basin • South: Norwegian Basin

  11. Time series of heat contentanomaly Lofoten Basin Norwegian Basin Solid lines: h = densitysurface (st= 27.9) Dashed lines: h = 500 m

  12. Relative contribution from changes in temperature and depth of thedensitysurface seasurface T(z) Using h = densitysurface -> contribution from changes in temperature and depth of st z = -h Changes in depthmayindicatechanges in theoceancirculation (e.g. Palmer and Haines, 2009; Rossby et al., 2009).

  13. Relative contribution to heat content from temperature and depth of st=27.9 South: Norwegian Basin North: Lofoten Basin 2004 2004 Mainlytemperaturecontributionexcept for someyears

  14. Anomaly in thedepth of st: 2004 Reflectchanges in theoceancirculation?

  15. Memory of theocean: autocorrelation Autocorrelation (oneyear lag) in heat content from detrended data.

  16. Interannualchanges(heat flux) South (Norwegian Basin) North (Lofoten Basin) RHC : Yearlychanges in the heat content

  17. Interannualchanges(heat flux) South (Norwegian Basin) North (Lofoten Basin) Air-sea heat flux Air-sea heat flux RHC : Yearlychanges in the heat content Q – North: One yearaveragedair-sea heat flux over the Lofoten Basin Q – South: One yearaveragedair-sea heat flux over theNorwegian Basin Air-sea heat fluxes from NCEP reanalysis data

  18. Summary • Heat content in theNorwegianSeaincreased during 1995-2010 withmaximum in 2004. • Changes in heat contentdependmainlyontemperaturechanges • Significantautocorrelation (oneyear time lag) in the Lofoten Basin • Changes in the heat content: linked to theair-sea heat flux, butotherprocesses (e.g. advection) arealsoimportant

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