Climatic conditions between 19 and 12 ka in the eastern Pyrenees, and wider implications for atmospheric circulation patterns in Europe

The chronology of the most extensive Late Pleistocene glaciation in the eastern Pyrenees is now well established, but climatic variations during the subsequent Last Glacial-to-Interglacial Transition (LGIT) are much less well documented. The aim of this research is to fill that gap. We present a new series of 22 Be-10 exposure ages from a sequence of moraines in the upper Ariege catchment, and update 64 previously published exposure ages from seven other valleys. Based on (i) geomorphological maps of successive generations of ice-marginal deposits and (ii) their age distributions, followed by (iii) glaciological modeling to infer corresponding mass-balance gradients and equilibrium line altitudes (ELAs), we reconstruct glacier behaviour in the eastern Pyrenees during the LGIT and retrieve paleoclimatic parameters for each glacial stillstand. Results document rapid deglaciation involving four relative still stands, with an ELA rise of similar to 410 m and increases in temperature and precipitation of similar to 4 degrees C and similar to 40%, respectively, between similar to 18 ka (Greenland Stadial GS-2.1b) and similar to 14.5 ka (Greenland Interstadial GI-1). A cold and dry environment prevailed from similar to 18 ka onward, and deglaciation was almost complete by GI-1. Only small glaciers persisted as late as similar to 12.3 ka in cirques where local conditions allowed it. These patterns are compatible with a transient Polar Front Jet Stream repositioning to latitudes of 40-42 degrees N between 18 and 16 ka, with Westerlies-dominated circulation not yet feeding precipitation to the mountain belt abundantly from the northwest, and outbursts of polar air meeting with cool sea waters in the western Mediterranean mostly suppressing precipitation from Mediterranean sources. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This study aims to fill the gap in documenting climatic variations during the Last Glacial-to-Interglacial Transition (LGIT) in the eastern Pyrenees. By reconstructing glacier behavior during this period, the results show rapid deglaciation with rising ELA, temperature, and precipitation, and a cold and dry environment persisting until the Greenland Interstadial GI-1.