The Impact of the Heinrich Stadial–Greenland Interstadial Transition during Marine Isotope Stage 3 on Large-Scale Atmospheric Circulation over Western Europe

Marine Isotope Stage 3 (MIS 3) is characterised by millennial-scale climate transitions, including Dansgaard–Oeschger events recorded in Greenland oxygen isotope ice cores and Heinrich events identified in marine sediment records. These changes are associated with variations in the Atlantic Meridional Overturning Circulation and are influenced by atmospheric circulation, with pronounced impacts on the regional paleoclimate in Europe.

Here we assess the changes in large-scale atmospheric circulation and regional climate during MIS 3, with a focus on the Iberian Peninsula. A freshwater hosing experiment was carried out using the global Earth system model NorESM1-F under boundary conditions representative of Greenland Interstadial 8 (GI-8; 38 kyr BP), capturing the transition from Heinrich Event 4 (H4) to GI-8. Dynamical downscaling was then performed for the Iberian Peninsula using the regional climate model WRF at 9 km horizontal resolution, forced by NorESM1-F output, to simulate regional circulation and associated temperature and precipitation patterns.

Preliminary results from the downscaled simulations suggest clear stadial–interstadial contrasts over Iberia, including a shift toward wetter winters and drier summers during cold stadials. These regional signals appear consistent with NorESM1-F–simulated changes in North Atlantic circulation, including shifts in the position and strength of the westerly jet and associated moisture transport during H4. This study offers an enhanced assessment of the regional climate in the Iberian Peninsula during MIS 3 by linking large-scale atmospheric dynamics with regional circulation and precipitation patterns.