Minor effect of meltwater on the ocean circulation during deglaciation
G. Lohmann1,2, K. Grosfeld1, M. Butzin1,2, P. Huybrechts3, and C. Zweck41Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany 2Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany 3Earth System Sciences & Departement Geografie, Vrije Universiteit Brussel, Brussel, Belgium 4Department of Hydrology and Water Resources, University of Arizona, Tucson, Arizona, USA
Received: 27 Jul 2012 – Accepted for review: 05 Aug 2012 – Discussion started: 16 Aug 2012
Abstract. Decaying Northern Hemisphere ice sheets during deglaciation affect the high latitude hydrological balance in the North Atlantic and therefore the ocean circulation after the Last Glacial Maximum. Surprisingly, geological data suggest that meltwater fluxes of about 14–20 m sea-level equivalent flushed into the North Atlantic without significantly influencing the Atlantic meridional overturning circulation. Using a three-dimensional ocean circulation model coupled to an energy balance model of the atmosphere, we investigate the response of the ocean circulation to spatio-temporal variable deglacial freshwater discharges. Freshwater inputs are simulated by a three-dimensional thermo-mechanical ice sheet model of the Northern Hemisphere. In our experiments, we find a strong sensitivity of the ocean circulation when the deglacial meltwater is injected into the surface layers yielding a quasi shut-down. On the other hand, the parameterization of huge sub-glacial outbursts as so-called hyperpycnal flows are mimicked through bottom injections in ocean models leading to a reduced sensitivity of the overturning circulation against freshwater perturbations and providing a consistent representation of the deglacial climate evolution.
Lohmann, G., Grosfeld, K., Butzin, M., Huybrechts, P., and Zweck, C.: Minor effect of meltwater on the ocean circulation during deglaciation, Earth Syst. Dynam. Discuss., 3, 801-825, doi:10.5194/esdd-3-801-2012, 2012.