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 degrees N, 10 degrees W), MD99-2331 and MD03-2697 (42 degrees N, 9 degrees W), and MD04-2845 (45 degrees N, 5 degrees 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 (CH4) during the last glacial period suggest a significant role of monsoon activity in determining CH4 emission from wetlands. (C) 2008 Elsevier Ltd. All rights reserved.