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

Wonsun Park & Mojib LatifLeibniz Institute of Marine Sciences, Kiel

THOR Annual Meeting, Paris, 25-26 November 2009

• Internal MOC variability•Multidecadal to Multicentennial scales

• External solar forced variability•Idealized experiments

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

Park et al. 2009 J. Clim.

Atlantic MOC(ctrl, 4000yrs)

Park and Latif 2008 GRL

MOC mode separation

LP 90yrs

BP 30-90yrs

SAT response to MOCMulticentennial vs. Multidecadal

Sea ice response to MOC

SH ice vs. MOC

SH Ice extent vs. MOC

LP 90yrs:

centennial to multicentennial

LP 185yrs

BP 90-185

Freshwater and Sea ice threshold

Park et al. in preparation

SSS

Climate impacts

Surface temperature SLP and wind stress

Park et al. in preparation

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

Summary1.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.

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