A coupled climate model simulation of Marine Isotope Stage 3 stadial climate 1Linné Flow Centre, Department of Mechanics, KTH, 10044 Stockholm, Sweden
22 Jun 2011
2Swedish Meteorological and Hydrological Institute, 60176 Norrköping, Sweden
3Swedish Nuclear Fuel and Waste Management Co (SKB), Box 5864, 10240 Stockholm, Sweden
4Swedish Meteorological and Hydrological Institute, 60176 Norrköping, Sweden
5LNEG – Laboratorio Nacional de Energia e Geologia, Unidade de Geologia Marinha, Estrada da Portela, Zambujal, 2610-143 Amadora, Portugal
6Department of Geological Sciences, Stockholm University, 10961 Stockholm, Sweden
Received: 20 Dec 2010 – Published in Clim. Past Discuss.: 11 Jan 2011Abstract. We present a coupled global climate model (CGCM) simulation,
integrated for 1500 yr to quasi-equilibrium, of a stadial (cold
period) within Marine Isotope Stage 3 (MIS 3). The simulated
Greenland stadial 12 (GS12; ~44 ka BP) annual
global mean surface temperature (Ts) is
5.5 °C lower than in the simulated recent past (RP)
climate and 1.3 °C higher than in the simulated Last
Glacial Maximum (LGM; 21 ka BP) climate.
The simulated GS12 is evaluated against proxy data and previous
modelling studies of MIS3 stadial climate. We show that the
simulated MIS 3 climate, and hence conclusions drawn regarding the
dynamics of this climate, is highly model-dependent.
The main findings are:
(i) Proxy sea surface temperatures (SSTs) are higher than simulated
SSTs in the central North Atlantic, in contrast to earlier simulations
of MIS 3 stadial climate in which proxy SSTs were found to be lower
than simulated SST.
(ii) The Atlantic Meridional Overturning Circulation (AMOC)
slows down by 50 % in the GS12 climate as compared
to the RP climate. This slowdown is attained without freshwater forcing
in the North Atlantic region, a method used in other studies to force
an AMOC shutdown.
(iii) El-Niño-Southern Oscillation (ENSO) teleconnections in
mean sea level pressure (MSLP) are significantly modified by GS12 and
LGM forcing and boundary conditions.
(iv) Both the mean state and variability of the simulated GS12
is dependent on the equilibration. The annual global mean Ts
only changes by 0.10 °C from model years 500–599 to the last
century of the simulation,
indicating that the climate system may be close to equilibrium already
after 500 yr of integration. However, significant regional
differences between the last century of the simulation and model years
500–599 exist. Further, the difference between simulated and proxy SST is
reduced from model years 500–599 to the last century of the
simulation. The results of the ENSO variability analysis is also shown
to depend on the equilibration.
Revised: 31 May 2011 – Accepted: 01 Jun 2011 – Published: 22 Jun 2011
Citation: Brandefelt, J., Kjellström, E., Näslund, J.-O., Strandberg, G., Voelker, A. H. L., and Wohlfarth, B.: A coupled climate model simulation of Marine Isotope Stage 3 stadial climate, Clim. Past, 7, 649-670, doi:10.5194/cp-7-649-2011, 2011.