Deuterium excess in polar ice: Insight from a zonally averaged ocean-atmosphere model

ANDRÉS ANTICO; OLIVIER MARCHAL; LAWRENCE A. MYSAK

Montreal

Congreso; MOCA-09: IAMAS-IAPSO-IACS 2009 Joint Assembly; 2009

IAMAS-IAPSO-IACS

Time-dependent solutions from a zonally averaged ocean-atmosphere model are examined to gain insight into the role of the hydrological cycle in the climatic response to Milankovitch forcing over the last 1 Myr. Including an active hydrological cycle in the model does not significantly change the response of annual mean surface air and ocean temperatures found in a previous model study in which the hydrological cycle was fixed. Likewise, the meridional fluxes of mass and heat in the ocean are not very sensitive to hydrological changes on Milankovitch time scales. The annual mean hydrological conditions respond mainly to obliquity changes. Thus, when the low-to-high latitude contrast in annual mean insolation is enhanced owing to a low obliquity, the sea surface temperature and evaporation increase (decrease) at low (high) latitudes, and the poleward moisture flux intensifies at midlatitudes. This hydrological response is consistent with a mechanism previously postulated by Vimeux et al. and Loutre et al. to explain the apparent imprint of obliquity changes in deuterium excess records from polar ice cores.