Internal and external variability of MOC in the Kiel Climate Model (ECHAM5/NEMO)

Wonsun Park (Mojib Latif group)Leibniz Institute of Marine Sciences, Kiel

THOR WP1 Meeting, Bergen, 1-2 October 2009

• Contents:– Model– Internal MOC variability (5000 yr control)

•Multidecadal to Multicentennial variability

– External variability (solar forced exp.)– Outlook

The Kiel Climate Model (KCM)ECHAM5 (T31L19), NEMO (0.5-2°)

Park et al. 2009 J. Clim.

Atlantic MOC(ctrl, 4000a)

Park and Latif 2008 GRL

MOC mode separation

SAT response to MOCMulticentennial vs. Multidecadal

Sea ice response to MOC

SH ice vs. MOC

Freshwater and Sea ice threshold

Park et al. in preparation

Western Atlantic SST, SSS

Summary (1/2)

1.Multidecadal variability is originated in the North Atlantic, whereas multicentennial variability is driven in the Southern Ocean.

2.Multicentennial Southern Ocean variability is related to the convective activities associated with sea ice capping threshold.

3.SO multicentennial signal is advected the North Atlantic, and provides stabilization (salinity) effect on MOC.

Millennial solar forcing experiments1. Solar forcing integration (4200a)

: periodic (P=1000a, ±2W/m2)2. ECHAM5/MLO simulation (2000a)

1000 years

4W/m2

Northern Hemisphere temperatureresponse to external solar forcing

Jones and Mann (2004) reconstruction

Latif et al. 2009 Met. Zeit.

Jones and Mann (2004)

MOC feedback onto NH-SAT

North Atlantic response

Northern Hemisphere SAT

IPCC 2007IPCC 2007

Summary (2/2)

1.Both internal variability and external (solar) forcing may explain the Northern Hemisphere SAT during the last millennium.

2.The MOC is strongly phase-locked to the solar forcing, and provides a strong negative feedback on the NH-SAT.

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)