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Sea-surface temperature, productivity and hydrological changes in the Northern Indian Ocean (Maldives) during the interval ~575-175 ka (MIS 14 to 7)

Sea-surface temperature, productivity and hydrological changes in the Northern Indian Ocean (Maldives) during the interval ~575-175 ka (MIS 14 to 7)
Sea-surface temperature, productivity and hydrological changes in the Northern Indian Ocean (Maldives) during the interval ~575-175 ka (MIS 14 to 7)

The South Asian Monsoon (SAM) drives seasonal changes in the atmospheric and ocean circulation of the tropical Indian Ocean, affecting precipitation on land and oceanic primary productivity. This work examined sediments from the International Ocean Discover Program (IODP) Site U1467 (IODP Expedition 359) located in the Maldives Inner Sea (Northern Indian Ocean) at a water depth of 487 m. The Maldives Inner Sea is a perfect location to study past changes in tropical climate and ocean circulation related to monsoon dynamics in the Equatorial Indian Ocean. This study focuses on the ~575-175 ka interval, from Marine Isotope Stage (MIS) 14 to 7, an important period for human evolution and dispersal to Eurasia. We reconstructed sea-surface temperature (SST), based on alkenone unsaturation index (U37 K'), hydrological changes, based on terrestrial input of n-alkanes, and past surface ocean productivity, based on total C37 alkenones concentration. The U37 K' -SST record shows a difference of about 1.5 °C between glacial and interglacial periods, clearly showing all stages and substages from MIS 14 to 7, and revealing a connection between ice sheets extension and SST at the equatorial region. The n-alkanes concentration and average chain length index indicate vegetation changes at the Indian Peninsula with drier conditions generally associated with glacial periods. Precipitation increases abruptly at the end of terminations, lasting for a variable time interval in each interglacial period, except for MIS 13. However, other mechanisms superimposed to the glacial-interglacial forcing, such as the Indian Ocean Dipole (IOD) mode, have been invoked to explain shorter-scale variability in precipitation over India. The total alkenone concentration record indicates that primary productivity at Site U1467 is strongly associated with orbital changes, probably related to the summer inter-tropical insolation gradient (SITIG, 23N-23S on June 21st). High primary productivity occurred during intervals of low SITIG, which resulted in strong inter-monsoon (April-May and October-November) Indian Ocean Equatorial Westerlies (IEW) and reduced precipitation in the equatorial region. This mechanism may also be related to the IOD, which affects the strength of the IEW.

Alkanes, Alkenones, Asian monsoon, Mid-Brunhes event, Pleistocene climate, SITIG
0031-0182
Alonso-Garcia, M.
7899abf2-8d23-4ffd-94af-e89cc73f154f
Rodrigues, T.
3ef199c5-4164-45cd-afe5-364bededd0e2
Abrantes, F.
6087b8bb-49c5-49f8-945b-9e1e1db48e14
Padilha, M.
d3656281-1b3e-40e7-a21f-66dbc24a933e
Alvarez-Zarikian, C. A.
32de001e-adab-4d1c-8b49-2620167fb2e0
Kunkelova, T.
32818c35-f763-4ba3-8640-b9334ad4ae6e
Wright, J. D.
d104ce8f-decf-44bb-b69e-4adf0b311262
Betzler, C.
24bd6d60-8449-4fd8-8a31-979cc75678d2
Alonso-Garcia, M.
7899abf2-8d23-4ffd-94af-e89cc73f154f
Rodrigues, T.
3ef199c5-4164-45cd-afe5-364bededd0e2
Abrantes, F.
6087b8bb-49c5-49f8-945b-9e1e1db48e14
Padilha, M.
d3656281-1b3e-40e7-a21f-66dbc24a933e
Alvarez-Zarikian, C. A.
32de001e-adab-4d1c-8b49-2620167fb2e0
Kunkelova, T.
32818c35-f763-4ba3-8640-b9334ad4ae6e
Wright, J. D.
d104ce8f-decf-44bb-b69e-4adf0b311262
Betzler, C.
24bd6d60-8449-4fd8-8a31-979cc75678d2

Alonso-Garcia, M., Rodrigues, T., Abrantes, F., Padilha, M., Alvarez-Zarikian, C. A., Kunkelova, T., Wright, J. D. and Betzler, C. (2019) Sea-surface temperature, productivity and hydrological changes in the Northern Indian Ocean (Maldives) during the interval ~575-175 ka (MIS 14 to 7). Palaeogeography, Palaeoclimatology, Palaeoecology, 536, [109376]. (doi:10.1016/j.palaeo.2019.109376).

Record type: Article

Abstract

The South Asian Monsoon (SAM) drives seasonal changes in the atmospheric and ocean circulation of the tropical Indian Ocean, affecting precipitation on land and oceanic primary productivity. This work examined sediments from the International Ocean Discover Program (IODP) Site U1467 (IODP Expedition 359) located in the Maldives Inner Sea (Northern Indian Ocean) at a water depth of 487 m. The Maldives Inner Sea is a perfect location to study past changes in tropical climate and ocean circulation related to monsoon dynamics in the Equatorial Indian Ocean. This study focuses on the ~575-175 ka interval, from Marine Isotope Stage (MIS) 14 to 7, an important period for human evolution and dispersal to Eurasia. We reconstructed sea-surface temperature (SST), based on alkenone unsaturation index (U37 K'), hydrological changes, based on terrestrial input of n-alkanes, and past surface ocean productivity, based on total C37 alkenones concentration. The U37 K' -SST record shows a difference of about 1.5 °C between glacial and interglacial periods, clearly showing all stages and substages from MIS 14 to 7, and revealing a connection between ice sheets extension and SST at the equatorial region. The n-alkanes concentration and average chain length index indicate vegetation changes at the Indian Peninsula with drier conditions generally associated with glacial periods. Precipitation increases abruptly at the end of terminations, lasting for a variable time interval in each interglacial period, except for MIS 13. However, other mechanisms superimposed to the glacial-interglacial forcing, such as the Indian Ocean Dipole (IOD) mode, have been invoked to explain shorter-scale variability in precipitation over India. The total alkenone concentration record indicates that primary productivity at Site U1467 is strongly associated with orbital changes, probably related to the summer inter-tropical insolation gradient (SITIG, 23N-23S on June 21st). High primary productivity occurred during intervals of low SITIG, which resulted in strong inter-monsoon (April-May and October-November) Indian Ocean Equatorial Westerlies (IEW) and reduced precipitation in the equatorial region. This mechanism may also be related to the IOD, which affects the strength of the IEW.

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More information

Accepted/In Press date: 13 September 2019
e-pub ahead of print date: 3 October 2019
Published date: 15 December 2019
Keywords: Alkanes, Alkenones, Asian monsoon, Mid-Brunhes event, Pleistocene climate, SITIG

Identifiers

Local EPrints ID: 437148
URI: http://eprints.soton.ac.uk/id/eprint/437148
ISSN: 0031-0182
PURE UUID: 85bd1a77-dc90-4151-b199-6fe08424e5ac

Catalogue record

Date deposited: 17 Jan 2020 17:36
Last modified: 25 Nov 2021 19:50

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Contributors

Author: M. Alonso-Garcia
Author: T. Rodrigues
Author: F. Abrantes
Author: M. Padilha
Author: C. A. Alvarez-Zarikian
Author: T. Kunkelova
Author: J. D. Wright
Author: C. Betzler

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