Contrasting impacts of Dansgaard–Oeschger events over a western European latitudinal transect modulated by orbital parameters

Terrestrial and marine proxies (pollen, planktic and benthic foraminiferal oxygen isotopes, alkenone- and foraminifer-derived sea-surface temperatures (SSTs), ice-rafted debris) from IMAGES deep-sea cores MD95-2042 and SU81-18 (37°N, 10°W), MD99-2331 and MD03-2697 (42°N, 9°W), and MD04-2845 (45°N, 5°W) show that western European and offshore environments were strongly affected by Dansgaard–Oeschger (D–O) and Heinrich (H) events. We concentrate here on latitudinal variability in the forest cover extent and composition of western Europe during the succession of D–O events, showing new pollen records for core MD04-2845 and for marine isotopic stages (MIS) 3 and 4 of core MD99-2331. In general, cold SSTs characteristic of Greenland stadials were contemporaneous with the expansion of semi-desert or steppic vegetation while Greenland interstadials were synchronous with the expansion of forest. Our data reveal that the amplitude of Atlantic and Mediterranean forest expansions differs for any given D–O warming during the glacial period (74–18 ka). In the western Mediterranean, D–O 16–17 and D–O 8 and 7 (corresponding to minima in precession) were associated with strong expansion of forest cover contrasting with weak expansion of forest cover during D–O 14 and 12; the opposite pattern is revealed at the Atlantic sites. Further north, the strongest Greenland warmings are recorded for D–O 19, 11 and 8. This contrasting latitudinal climatic scenario is compared with other northern hemisphere records, revealing similarities between the Mediterranean climate and the Asian monsoon regime, which may relate to a summer atmospheric teleconnection between the two regions comparable to the present-day situation. Parallels between Mediterranean climate enhancement and peaks in global methane (CH 4) during the last glacial period suggest a significant role of monsoon activity in determining CH 4 emission from wetlands.