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THOR WP1 Meeting, Bergen, 1-2 October 2009

Internal and external variability of MOC in the Kiel Climate Model (ECHAM5/NEMO) Wonsun Park (Mojib Latif group) Leibniz Institute of Marine Sciences, Kiel. Contents: Model Internal MOC variability (5000 yr control) Multidecadal to Multicentennial variability

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THOR WP1 Meeting, Bergen, 1-2 October 2009

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  1. Internal and external variability of MOC in the Kiel Climate Model (ECHAM5/NEMO)Wonsun Park (Mojib Latif group)Leibniz Institute of Marine Sciences, Kiel • Contents: • Model • Internal MOC variability (5000 yr control) • Multidecadal to Multicentennial variability • External variability (solar forced exp.) • Outlook THOR WP1 Meeting, Bergen, 1-2 October 2009

  2. The Kiel Climate Model (KCM)ECHAM5 (T31L19), NEMO (0.5-2°) Park et al. 2009 J. Clim.

  3. Atlantic MOC(ctrl, 4000a) Park and Latif 2008 GRL

  4. MOC mode separation

  5. SAT response to MOCMulticentennial vs. Multidecadal

  6. SH icevs. MOC Sea ice response to MOC

  7. Freshwater and Sea ice threshold Park et al. in preparation

  8. Western Atlantic SST, SSS

  9. Summary (1/2) • Multidecadal variability is originated in the North Atlantic, whereas multicentennial variability is driven in the Southern Ocean. • Multicentennial Southern Ocean variability is related to the convective activities associated with sea ice capping threshold. • SO multicentennial signal is advected the North Atlantic, and provides stabilization (salinity) effect on MOC.

  10. 1000 years 4W/m2 Millennial solar forcing experiments • Solar forcing integration (4200a) : periodic (P=1000a, ±2W/m2) • ECHAM5/MLO simulation (2000a)

  11. Northern Hemisphere temperatureresponse to external solar forcing Jones and Mann (2004) Jones and Mann (2004) reconstruction Latif et al. 2009 Met. Zeit.

  12. MOC feedback onto NH-SAT

  13. North Atlantic response

  14. Northern Hemisphere SAT IPCC 2007 IPCC 2007

  15. Summary (2/2) • Both internal variability and external (solar) forcing may explain the Northern Hemisphere SAT during the last millennium. • The MOC is strongly phase-locked to the solar forcing, and provides a strong negative feedback on the NH-SAT.

  16. Outlook • Idealized solar forced experiments • ±2W/m2,±1W/m2 (1000yr cycle) • New integrations (T42/ORCA2) • Preindustrial: 2000yr • Last millennium simulations: all forcings (solar, GHG) without carbon cycle (planned)

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