Published in:
Climate of the Past, 14 (2018) 10, Seite 1405-1415
Language:
English
DOI:
10.5194/cp-14-1405-2018
ISSN:
1814-9332
Origination:
Footnote:
Description:
Abstract. The last deglaciation represents the most recent example ofnatural global warming associated with large-scale climate changes. Inaddition to the long-term global temperature increase, the last deglaciationonset is punctuated by a sequence of abrupt changes in the NorthernHemisphere. Such interplay between orbital- and millennial-scale variabilityis widely documented in paleoclimatic records but the underlying mechanismsare not fully understood. Limitations arise from the difficulty inconstraining the sequence of events between external forcing, high- and low-latitude climate, and environmental changes. Greenland ice cores provide sub-decadal-scale records across the lastdeglaciation and contain fingerprints of climate variations occurring indifferent regions of the Northern Hemisphere. Here, we combine new iced-excess and 17O-excess records, tracing changes in themidlatitudes, with ice δ18O records of polar climate. WithinHeinrich Stadial 1, we demonstrate a decoupling between climatic conditionsin Greenland and those of the lower latitudes. While Greenland temperatureremains mostly stable from 17.5 to 14.7 ka, significant change in the midlatitudes of the northern Atlantic takes place at ∼16.2 ka, associatedwith warmer and wetter conditions of Greenland moisture sources. We show thatthis climate modification is coincident with abrupt changes in atmosphericCO2 and CH4 concentrations recorded in an Antarctic icecore. Our coherent ice core chronological framework and comparison with otherpaleoclimate records suggests a mechanism involving two-step freshwaterfluxes in the North Atlantic associated with a southward shift of theIntertropical Convergence Zone.