Abstract. The last deglaciation represents the most recent example of
natural global warming associated with large-scale climate changes. In
addition to the long-term global temperature increase, the last deglaciation
onset is punctuated by a sequence of abrupt changes in the Northern
Hemisphere. Such interplay between orbital- and millennial-scale variability
is widely documented in paleoclimatic records but the underlying mechanisms
are not fully understood. Limitations arise from the difficulty in
constraining 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 last
deglaciation and contain fingerprints of climate variations occurring in
different regions of the Northern Hemisphere. Here, we combine new ice
d-excess and 17O-excess records, tracing changes in the
midlatitudes, with ice δ18O records of polar climate. Within
Heinrich Stadial 1, we demonstrate a decoupling between climatic conditions
in Greenland and those of the lower latitudes. While Greenland temperature
remains mostly stable from 17.5 to 14.7 ka, significant change in the midlatitudes of the northern Atlantic takes place at ∼16.2 ka, associated
with warmer and wetter conditions of Greenland moisture sources. We show that
this climate modification is coincident with abrupt changes in atmospheric
CO2 and CH4 concentrations recorded in an Antarctic ice
core. Our coherent ice core chronological framework and comparison with other
paleoclimate records suggests a mechanism involving two-step freshwater
fluxes in the North Atlantic associated with a southward shift of the
Intertropical Convergence Zone.
Biomarker records from core GH02-1030 off Tokachi in the northwestern Pacific over the last 23,000 years: Environmental changes during the last deglaciation