Increased contribution of the southern sourced water to the equatorial Indian Ocean during the glacial intervals
Abstract
The global thermohaline circulation modulates availability of oxygen and carbon-dioxide in the deep and intermediate waters of the world oceans. The presence of perennial intermediate water oxygen minimum zone in the northern Indian Ocean is partly attributed to the restricted circulation and thus limited oxygen replenishment. The knowledge of the changes in the Indian Ocean circulation in the past can help to assess this link better. Here, we infer deep water circulation changes from the northern Indian Ocean over the last three glacial-interglacial cycles by using the stable oxygen (δ18O) and carbon (δ13C) isotopic ratio of benthic foraminifera. The glacial-interglacial difference in δ18O was consistent during the last three transitions. This estimate is comparable with that of the CLIMAP which reported an average benthic oxygen isotopic change of 2.0‰ for the Indian Ocean region. We further report that the amplitude of glacial-interglacial deep water δ18O changes in the equatorial Indian Ocean was comparatively higher than the global average glacial-interglacial δ18O variations (1.9‰) implying that the Indian Deep Water was significantly cooler during glacial intervals. The difference in δ13C was ~1.0‰, during the last three transitions. Based on the modern day composition of the Indian Deep water, we infer that during the glacial intervals, the Southern Ocean water constituted the major component of the Indian Deep Water whereas the contribution of the North Atlantic Deep Water to the Indian Deep Water was considerably reduced.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMPP13B1434S
- Keywords:
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- 1622 Earth system modeling;
- GLOBAL CHANGE;
- 1630 Impacts of global change;
- GLOBAL CHANGE;
- 1635 Oceans;
- GLOBAL CHANGE;
- 4901 Abrupt/rapid climate change;
- PALEOCEANOGRAPHY