Links between tropical rainfall and North Atlantic climate during the last glacial period
Résumé
During the last glacial period, the North Atlantic region
experienced pronounced, millennial-scale alternations between cold, stadial conditions and milder interstadial
conditions—commonly referred to as Dansgaard–Oeschger
oscillations—as well as periods of massive iceberg discharge
known as Heinrich events1
. Changes in Northern Hemisphere
temperature, as recorded in Greenland2–4, are thought to have
affected the location of the Atlantic intertropical convergence
zone5,6 and the strength of the Indian summer monsoon7,8
.
Here we use high-resolution records of sediment colour—a
measure of terrigenous versus biogenic content—from the
Cariaco Basin off the coast of Venezuela and the Arabian
Sea to assess teleconnections with the North Atlantic climate
system during the last glacial period. The Cariaco record
indicates that the intertropical convergence zone migrated
seasonally over the site during mild stadial conditions, but was
permanently displaced south of the basin during peak stadials
and Heinrich events. In the Arabian Sea, we find evidence of
a weak Indian summer monsoon during the stadial events.
The tropical records show a more variable response to North
Atlantic cooling than the Greenland temperature records. We
therefore suggest that Greenland climate is especially sensitive
to variations in the North Atlantic system—in particular sea-ice
extent—whereas the intertropical convergence zone and Indian
monsoon system respond primarily to variations in mean
Northern Hemisphere temperature.