North Atlantic forcing of tropical Indian Ocean climate.
The response of the tropical climate in the Indian Ocean realm to abrupt climate change events in the North Atlantic Ocean is contentious. Repositioning of the intertropical convergence zone is thought to have been responsible for changes in tropical hydroclimate during North Atlantic cold spells, but the dearth of high-resolution records outside the monsoon realm in the Indian Ocean precludes a full understanding of this remote relationship and its underlying mechanisms. Here we show that slowdowns of the Atlantic meridional overturning circulation during Heinrich stadials and the Younger Dryas stadial affected the tropical Indian Ocean hydroclimate through changes to the Hadley circulation including a southward shift in the rising branch (the intertropical convergence zone) and an overall weakening over the southern Indian Ocean. Our results are based on new, high-resolution sea surface temperature and seawater oxygen isotope records of well-dated sedimentary archives from the tropical eastern Indian Ocean for the past 45,000 years, combined with climate model simulations of Atlantic circulation slowdown under Marine Isotope Stages 2 and 3 boundary conditions. Similar conditions in the east and west of the basin rule out a zonal dipole structure as the dominant forcing of the tropical Indian Ocean hydroclimate of millennial-scale events. Results from our simulations and proxy data suggest dry conditions in the northern Indian Ocean realm and wet and warm conditions in the southern realm during North Atlantic cold spells.
MARUM-Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany.
Mahyar
M
Mohtadi
MARUM-Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany.
Matthias
M
Prange
Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA.
Delia W
DW
Oppo
Department of Oceanography, University of Concepción, Concepción, Chile.
Ricardo
R
De Pol-Holz
MARUM-Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany.
Ute
U
Merkel
MARUM-Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany.
Xiao
X
Zhang
MARUM-Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany.
Stephan
S
Steinke
Federal Institute for Geosciences and Natural Resources, 30655 Hannover, Germany.
Andreas
A
Lückge
D000351:Africa, Eastern; D000388:Air; D001267:Atlantic Ocean; D001893:Borneo; D019015:Geologic Sediments / Q000737:chemistry; D006116:Greenland; D049672:History, 19th Century; D049673:History, 20th Century; D049674:History, 21st Century; D049690:History, Ancient; D006813:Humidity; D062070:Hydrology; D046448:Ice Cover; D019156:Indian Ocean; D007214:Indonesia; D060106:Lakes; D008962:Models, Theoretical; D010103:Oxygen Isotopes; D011891:Rain; D054712:Salinity; D012621:Seasons; D012623:Seawater / Q000032:analysis / Q000737:chemistry; D013696:Temperature; D013997:Time Factors; D014329:Tropical Climate; D014872:Water Movements
D010103:Oxygen Isotopes