TY - JOUR
T1 - Abrupt intensification of the SW Indian Ocean monsoon during the last deglaciation
T2 - Constraints from Th, Pa, and He isotopes
AU - Marcantonio, Franco
AU - Anderson, Robert F.
AU - Higgins, Sean
AU - Fleisher, Martin Q.
AU - Stute, Martin
AU - Schlosser, Peter
N1 - Funding Information:
We thank F. Sirocko for generously providing us with samples from Arabian Sea core 74KL. We are grateful to M. Frank, R. François, and F. Sirocko for constructive reviews. This work was supported by NSF Grants OCE 97-11870 and OCE 97-14898. L-DEO noble gas laboratory support was provided by the W.M. Keck Foundation and the NSF. [FA]
PY - 2001
Y1 - 2001
N2 - Sediments from western Arabian Sea core 74KL representing the last 23 ka were analyzed for helium, thorium, and protactinium isotopes. Assuming global average fluxes of extraterrestrial 3He and 230Th, the average 3He-derived sediment mass accumulation rate (MAR) is a factor of 1.8 higher than the average 230Th-derived MAR. 3He- and 230Th-derived MARs converge, however, during the Younger Dryas (YD) and during the peak of the early Holocene humid interval. These features, not seen anywhere else in the world, probably reflect a combination of climate-driven changes in the flux of 230Th and 3He. Ratios of xs231 Pa/xs230Th, proxies of paleoproductivity, are lowest during the last glacial maximum (LGM), and increase abruptly during the Bolling-Allerod. Later, following a sudden decrease to near-LGM values during the YD, they rise abruptly to maximum values for the entire record in the early Holocene. We hypothesize that low xs231 Pa/sx230Th ratios reflect low productivity due to the decreased intensity of the SW monsoon, whereas the opposite is true for high ratios. The correlation between Arabian Sea productivity and monsoonal upwelling, on the one hand, and North Atlantic climate variability, on the other, suggests a linkage between high- and low-latitude climates caused by changing patterns of atmospheric circulation.
AB - Sediments from western Arabian Sea core 74KL representing the last 23 ka were analyzed for helium, thorium, and protactinium isotopes. Assuming global average fluxes of extraterrestrial 3He and 230Th, the average 3He-derived sediment mass accumulation rate (MAR) is a factor of 1.8 higher than the average 230Th-derived MAR. 3He- and 230Th-derived MARs converge, however, during the Younger Dryas (YD) and during the peak of the early Holocene humid interval. These features, not seen anywhere else in the world, probably reflect a combination of climate-driven changes in the flux of 230Th and 3He. Ratios of xs231 Pa/xs230Th, proxies of paleoproductivity, are lowest during the last glacial maximum (LGM), and increase abruptly during the Bolling-Allerod. Later, following a sudden decrease to near-LGM values during the YD, they rise abruptly to maximum values for the entire record in the early Holocene. We hypothesize that low xs231 Pa/sx230Th ratios reflect low productivity due to the decreased intensity of the SW monsoon, whereas the opposite is true for high ratios. The correlation between Arabian Sea productivity and monsoonal upwelling, on the one hand, and North Atlantic climate variability, on the other, suggests a linkage between high- and low-latitude climates caused by changing patterns of atmospheric circulation.
KW - Climate change
KW - Helium
KW - Isotopes
KW - Monsoons
KW - Protactinium
KW - Thorium
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U2 - 10.1016/S0012-821X(00)00342-3
DO - 10.1016/S0012-821X(00)00342-3
M3 - Article
AN - SCOPUS:0035112319
SN - 0012-821X
VL - 184
SP - 505
EP - 514
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
IS - 2
ER -