A 300 kyr record of upwelling off Oman during the late Quaternary; evidence of the Asian southwest monsoon

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doi: 10.1029/93PA00256
Author(s): Anderson, David M.; Prell, Warren L.
Author Affiliation(s): Primary:
National Oceanic and Atmospheric Administration, Paleoclimatology Program, Boulder, CO, United States
Brown University, United States
Volume Title: Paleoceanography
Source: Paleoceanography, 8(2), p.193-208. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0883-8305 CODEN: POCGEP
Note: In English. 39 refs.; illus. incl. 5 tables, sketch maps
Summary: In the northwest Arabian Sea upwelling occurs each summer, driven by the strong SW monsoon winds. Upwelling results in high biological productivity and a distinctive assemblage of plankton species in the surface waters off Oman that are preserved in the sediments along the Oman continental margin, creating a geologic record of monsoon-driven upwelling. Sediments recovered from the Oman continental margin during Ocean Drilling Program leg 117 provide an opportunity to examine how upwelling has varied during the late Quaternary, spanning a longer interval than piston cores recovered prior to the ODP cruise. Variations in foraminifer shell accumulation and in the relative abundance of Globigerina bulloides indicate dominant cycles of variation at 1/100 kyr, the dominant frequency of glacial-interglacial variations, and at 1/23 kyr, the frequency of precessionally driven cycles in seasonal insolation. The strongest monsoon winds (indicated by increased upwelling) occurred during interglacial times when perihelion was aligned with the summer solstice, an orbital change that increased the insolation received during summer in the northern hemisphere. During glacial times upwelling was reduced, and although the precessional cycles were still present their amplitude was smaller. At both frequencies the upwelling cycles are in phase with minimum ice volume, evidence that glacial-interglacial climate changes also include changes to the climate system that influence the low-latitude monsoon. We attribute the decrease in the monsoon winds observed during glacial times to changes in bare land albedo over Asia and/or to changes in the areal extent and seasonal cycle in Asian snow cover that decrease the summer land-sea temperature contrast. Other mechanisms may also be involved. These new upwelling time series differ substantially from previous results, however the previous work relied on cores located farther offshore where upwelling is less intense and other physical mechanisms become important. Our results support the observations derived from atmospheric general circulation models of the atmosphere that indicate that both glacial boundary conditions, and the strength of summer insolation are important variables contributing to cycles in the monsoon winds during the late Quaternary. Copyright 1993 by the American Geophysical Union.
Year of Publication: 1993
Research Program: ODP Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; 24 Surficial Geology, Quaternary Geology; Arabian Peninsula; Arabian Sea; Asia; Bioclastic sedimentation; Continental margin; Cores; Cycles; Foraminifera; Glacial environment; Glaciomarine environment; Indian Ocean; Interglacial environment; Invertebrata; Leg 117; Magnetic susceptibility; Marine environment; Marine sediments; Microfossils; Monsoons; ODP Site 723; Ocean Drilling Program; Oman; Paleo-oceanography; Paleocirculation; Paleoclimatology; Paleomagnetism; Planktonic taxa; Protista; Sedimentation; Sediments; Storm environment; Upwelling
Coordinates: N180304 N180305 E0573634 E0573633
Record ID: 1993028858
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute.