A 300 kyr record of upwelling off Oman during the Late Quaternary: evidence of the Asian southwest monsoon


Autoria(s): Anderson, David M; Prell, Warren L
Cobertura

MEDIAN LATITUDE: 18.051800 * MEDIAN LONGITUDE: 57.608415 * SOUTH-BOUND LATITUDE: 18.051800 * WEST-BOUND LONGITUDE: 57.608100 * NORTH-BOUND LATITUDE: 18.051800 * EAST-BOUND LONGITUDE: 57.609000 * DATE/TIME START: 1987-09-15T11:45:00 * DATE/TIME END: 1987-09-19T14:15:00

Data(s)

03/06/1993

Resumo

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.

Formato

application/zip, 2 datasets

Identificador

https://doi.pangaea.de/10.1594/PANGAEA.695230

doi:10.1594/PANGAEA.695230

Idioma(s)

en

Publicador

PANGAEA

Direitos

CC-BY: Creative Commons Attribution 3.0 Unported

Access constraints: unrestricted

Fonte

Supplement to: Anderson, David M; Prell, Warren L (1993): A 300 kyr record of upwelling off Oman during the Late Quaternary: evidence of the Asian southwest monsoon. Paleoceanography, 8(2), 193-208, doi:10.1029/93PA00256

Palavras-Chave #117-723A; 117-723B; Age model; Age model, composite; Age model is based on oxygen isotope correlation to the Specmap record (Imbrie et al., 1984) and the benthic isotope composite record (Martinson et al., 1982).; Arabian Sea; calculated ages; Depth; DEPTH, sediment/rock; DRILL; Drilling/drill rig; Event; Joides Resolution; Leg117; Ocean Drilling Program; ODP; Suscept; Susceptibility; unit not given
Tipo

Dataset