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North Atlantic Subpolar Gyre forcing on the fresh water exchange with the Arctic Ocean

North Atlantic Subpolar Gyre forcing on the fresh water exchange with the Arctic Ocean. Christophe HERBAUT and Marie-Noëlle HOUSSAIS LOCEAN, UPMC, PARIS Contribution to WP 2.3. hindcasts simulation with ORCA05 (regional configuration) forced by the ERA40 reanalysis

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North Atlantic Subpolar Gyre forcing on the fresh water exchange with the Arctic Ocean

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  1. North Atlantic Subpolar Gyre forcing on the fresh water exchange with the Arctic Ocean Christophe HERBAUT and Marie-Noëlle HOUSSAIS LOCEAN, UPMC, PARIS Contribution to WP 2.3 THOR meeting Paris November 25-26, 2009

  2. hindcasts simulation with ORCA05 (regional configuration) forced by the ERA40 reanalysis sensitivity experiments to NAO-like atmospheric forcing (10 years Link to the MOC Analysis the fresh water content variability of the Arctic-North Atlantic Ocean based upon : LOCEAN regional Arctic North Atlantic model (ORCA05) THOR meeting Paris November 25-26, 2009

  3. GSA Hindcast experiment : salinity (200 – 500 m) EOF analysis 1978-2001 THOR meeting Paris November 25-26, 2009

  4. Subpolar gyre salinity : link to NAO 2003 1993 1998 1988 WOCE A01E 1992 OVIDE 2004 Thierry et al., 2008 Salinity at 20°W Johnson et Gruber, 2008 THOR meeting Paris November 25-26, 2009

  5. NAO+ and NAOneutral composite years NAO index : ERA40 reanalysis NAO+ : 1973, 1976, 1983,1989, 1990, 1992, 1993, 1995, 2000 NAO neutral : 1959, 1968, 1972, 1981, 1982, 1984, 1986, 1988, 1998 THOR meeting Paris November 25-26, 2009

  6. Composite patterns (NAO+ - NAOneutral) Wind stress Winter (NDJFM) Heat flux Winter (NDJFM) THOR meeting Paris November 25-26, 2009

  7. Salinity anomalies (NAO+ - NAOneutral) Wind-only Wind-only All fluxes All fluxes Eastern gyre All fluxes Western gyre 0-200 m Wind-only EOF 1 200-500 m Herbaut and Houssais, 2009 THOR meeting Paris November 25-26, 2009

  8. Regional versus global wind stress forcing Arctic wind-only Wind-only 200-500 m salinity anomalies THOR meeting Paris November 25-26, 2009

  9. Intergyre gyre (Marshall et al., 2001) THOR meeting Paris November 25-26, 2009

  10. Sea Surface Height anomalies – Gyre Index Wind-only All fluxes All fluxes Wind-only Gyre index Hakkinen and Rhines, 2004 THOR meeting Paris November 25-26, 2009

  11. Progression of salinity anomalies around the SPG Year 4 Iceland basin Western European Basin Year 6 Year 8 --- Advection by velocity anomalies -.-. Advection of salinity anomalies THOR meeting Paris November 25-26, 2009

  12. Arctic fresh water content EOF analysis : 1959-2001 THOR meeting Paris November 25-26, 2009

  13. Fresh water content and NAO NAO leads NAO lags PC1 PC2 PC3 THOR meeting Paris November 25-26, 2009

  14. Fresh water export through the CAA Annual mean THOR meeting Paris November 25-26, 2009

  15. Fresh water export through the CAA Relative contributions of velocity and salinity anomalies Normalized transports Volume transport CAA FW transport Davis Strait (S<34.6) THOR meeting Paris November 25-26, 2009

  16. Outflow to Lancaster Sound Lancaster McClure Byam Martin Penny Amundsen THOR meeting Paris November 25-26, 2009

  17. Upstream and downstream forcing on Lancaster outflow Correlation Lancaster outflow with: . SSH McClure . SSH Lancaster THOR meeting Paris November 25-26, 2009

  18. Downstream forcing on Nares Srait outflow Correlation Nares outflow with SSH SSH Nares-SSH Smith SSH Nares SSH Smith THOR meeting Paris November 25-26, 2009

  19. SSH forcing on Lancaster outflow SSH on SSH in McClure SSH climatology THOR meeting Paris November 25-26, 2009

  20. Link to arctic fresh water content (FWC) Correlation FWC PC3-Lancaster Regression FWC on Lancaster outflow FW content - EOF3 THOR meeting Paris November 25-26, 2009

  21. Subpolar SSH forcing on Nares Strait transport SSH regressed on transport in Nares Strait SSH regressed on SSH in Smith Sound  Only weak SSH forcing in central Arctic THOR meeting Paris November 25-26, 2009

  22. Mechanisms of SSH variability in Baffin Bay Air-sea heat flux on SSH in Smith Sound  Lagged response of Baffin Bay to buoyancy driven SSH changes in the Labrador Sea THOR meeting Paris November 25-26, 2009

  23. Atmospheric modes driving CAA variability SLP on SSH in Smith Sound SLP on Lancaster outflow  NAO-like SLP patterns THOR meeting Paris November 25-26, 2009

  24. Idealized NAO experiments  Arctic/subpolar influence on CAA outflow  Wind stress/buoyancy forcing on CAA outflow 3 sensitivity experiments : • Wind stress-only • Buoyancy forcing (SAT and SHU)-only • Buoyancy forcing restricted to south of Davis and GISR THOR meeting Paris November 25-26, 2009

  25. Idealized NAO experiments Buoyancy Atlantic Wind-only Buoyancy • Wind driven Arctic SSH anomalies  SSH pattern impacting on McClure • Buoyancy driven subpolar anomalies SSH pattern impacting on Nares THOR meeting Paris November 25-26, 2009

  26. Time evolution of the response Distribution between passages Total CAA outflow WIND BUOYANCY BUOYANCY_ATL --- Nares Strait __ Lancaster Sound THOR meeting Paris November 25-26, 2009

  27. Meridional overturning anomalies Wind-only Year 1-3 Year 4-6 All forcings THOR meeting Paris November 25-26, 2009

  28. Wind driven variability of SPG is able to drive east-west redistribution of the upper fresh water content within the gyre wich are linked to shifts in the NAC rather than gyre intensification Transport of upper salinity anomalies by the mean gyre circulation may impact on the subsurface fresh water content in the Labrador Sea and on the salinity of the inflow of Atlantic water to the Arctic  potential control of the strength of the THC Buoyancy driven SSH changes in the Labrador Sea may propagate to Baffin Bay, therefore exerting a remote control on the FW export through the Canadian Archipelago. This effect adds to that of the wind-driven changes linked to the upstream variability of the Arctic fresh water content. All these processes have strong link to the NAO, although with different timing. Conclusions THOR meeting Paris November 25-26, 2009

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