Hydrological change in Southern Europe responding to increasing North Atlantic overturning during Greenland Stadial 1

Abstract

Greenland Stadial 1 (GS-1) was the last of a long series of severe cooling episodes in the Northern Hemisphere during the last glacial period. Numerous North Atlantic and European records reveal the intense environmental impact of that stadial whose origin is attributed to an intense weakening of the Atlantic Meridional Overturning Circulation (AMOC) in response to freshening of the North Atlantic (Broecker et al., 1988). Recent high-resolution studies of European lakes revealed a mid GS-1 transition in the climatic regimes (Bakke et al., 2009; Lane et al., 2013). The geographical extension of such atmospheric changes and their potential coupling with ocean dynamics still remains unclear. Here we use a sub-decadally resolved stalagmite record from the northern Iberian Peninsula to further investigate the timing and forcing of this transition. A solid interpretation of the environmental changes detected in this new, accurately dated, stalagmite record is based on a parallel cave monitoring exercise. This record reveals a gradual transition from dry to wet conditions starting at 12,500 b2k in parallel to a progressive warming of the subtropical Atlantic ocean (Schmidt et al., 2011). The observed atmospheric changes are proposed to be led by a progressive resumption of the North Atlantic convection and highlight the complex regional signature of GS-1, very distinctive to previous stadial events.