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Sub-Polar Gyre Variability and AMOC Linkages

Sub-Polar Gyre Variability and AMOC Linkages. Paul G. Myers Department of Earth and Atmospheric Sciences, University of Alberta. Funding support by:. Acknowledgements. Collaborators Mads Ribergaard (DMI) Anne-Marie Treguier (Ifremer) Claus Boening and Arne Biastoch (IFM-Geomar)

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Sub-Polar Gyre Variability and AMOC Linkages

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  1. Sub-Polar Gyre Variability and AMOC Linkages Paul G. Myers Department of Earth and Atmospheric Sciences, University of Alberta Funding support by:

  2. Acknowledgements • Collaborators • Mads Ribergaard (DMI) • Anne-Marie Treguier (Ifremer) • Claus Boening and Arne Biastoch (IFM-Geomar) • Nilgun Kulan (ASL Environmental Sciences) • Post-Doc • Arjen Terwisscha van Scheltinga • Graduate Students • Sanjay Rattan • John Wang • Xianmin Hu • Colin More

  3. Outline • West Greenland Current • Historical Reanalysis of Labrador Sea • Labrador Sea Water Formation • Transport at 53N • Links to MOC • NEMO Modelling • FW Pathways from CAA • Drift and circulation

  4. West Greenland Current and Disko Bay

  5. Data Sets • Kulan and Myers, 2009 • Climatological mapping of Labrador Sea (isopyncal framework) • Velocities from data assimilation (spectral nudging) into regional OGCM • Triad analysis from objective analysis of 3 year running means

  6. Labrador Sea Water Formation • Subduction based on: • I) ML retreat • II) Convergence of horizontal transport into ML • S > 0 subduction • S < 0 entrainment into ML • Later transferred into interior through deep convection Mean: 1.2 ± 0.2 Sv (27.74-27.82) and 0.8 ± 0.2 Sv (26.68-27..74)

  7. Export in DWBC at 53N 1996-1999 Dengler et al, 2006 1958-1999

  8. Variability in DWBC at 53N Reduction of 1.7 Sv over 1949-1999 in ISOW, DSOW layers

  9. Historical Reanalysis MOC • Positive trend of 0.01 to 0.03 Sv/year • Coherence between SP MOC variability at different latitudes • 55 to 50N: 0.91 • 55 to 45N: 0.48 • MOC and LSW variability correlated • 0.38 at 55N at a lag of 3 years • 0.42 at 45N at a lag of 3 years • Little change in correlation as signal rapidly propagates south in DWBC? • MOC correlated with LSW transport in DWBC at 53N, with 0.3-0.5, max at lags of 7-8 years • MOC strongly correlated with DWBC transport at 53N • 0.45-0.63 in density space at short lags Density Space

  10. North Atlantic Modelling Framework ORCA025 Global ¼ Degree • 1958-2004 hindcasts (CORE/DSF3) Structured - NEMO • perpetual year sensitivity runs • 1958-04 hindcast (CORE) NATL025 North Atlantic: 5-12 km SPG • 1988-2006 (CORE) • 2001-2008 (RECAST- GEM) • 1958-2004 (HIRHAM) NATL12 North Atlantic: 3- 6 km SPG resolution

  11. Arctic/CAA Modelling Framework Structured - NEMO ORCA025 Global ¼ Degree • 1958-2004 hindcasts (CORE/DSF3) • 1970-2007 hindcast (CORE) • 2000-2100 (CCCMA) ARC Pan-Arctic: 10-15 Km resolution • 1988-2006 (CORE) • 2001-2008 (RECAST- GEM) • 1958-2004 (HIRHAM) CAA Canadian Arctic Archipelago: 6.5- 9.5 km resolution

  12. Lagrangian Float Trajectories for Pacific Water Inflow

  13. Lagrangian Float Trajectories for Hudson Strait Inflow NATL12 ORCA025 1980 1990

  14. Lagrangian Float Trajectories for CAA Inflow ORCA025 ORCA025 ORCA025 Lancaster Sound Nares Strait NATL12

  15. Model Current Variability along AR7W ORCA025 – 47 years NATL12 – 2 years Fischer et al, 2010

  16. Drift in NEMO Configurations • Still significant drift in ice-ocean models • Regional/global configurations – same behavior • Perpetual Year/Inter-annual forcing – same behavior • 2 Stages • I) First 2-3 years – same in all experiments – probably related to inconsistencies with initial conditions • II) 3-15 years – significant differences between runs Rattan et al. , Ocean Modelling, 2010

  17. Early Stages of the Model Drift Outer Domain Cumulative salt transport into interior Inner Domain

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