Grain Size Constraints on Glacial Circulation from the Vema Channel and Brazil Margin, Southwest Atlantic
Abstract
Knowledge of past deep-ocean current speeds may be used to help constrain changes in deep-ocean circulation rates and pathways, helping us to inform our understanding of changes in the AMOC on glacial-interglacial timescales. Of particular interest is the paleo-flow speed of southern-sourced deep-water, which may have acted as a carbon store during the last glacial period. An important location in the northward transport of southern-sourced bottom water is the Vema Channel, which divides the Argentine and Brazil basins in the South Atlantic. We revisit previous studies of paleo-flow in Vema Channel using updated techniques in grain size analysis (i.e. mean sortable silt grain size), in Vema Channel cores and cores from the Brazil margin. Furthermore, we update the interpretation of the previous grain size studies in the light of many years further research into the glacial circulation of the deep Atlantic. Our results are broadly consistent with the existing data and suggest that during the last glacial period there was slightly more vigorous intermediate to mid-depth (shallower than 2600 m) circulation in the South Atlantic Ocean than in the Holocene, whereas below 3500 m the circulation was generally more sluggish. Increased glacial flow speed on the eastern side of the Vema Channel was likely related to an increase in northward velocity of AABW in the channel. An increase in Antarctic Bottom Water flow through the Vema Channel may have helped to sustain the large volume of southern-sourced deep-water in the Atlantic during the glacial period.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMPP21E1458S
- Keywords:
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- 1616 Climate variability;
- GLOBAL CHANGEDE: 1626 Global climate models;
- GLOBAL CHANGEDE: 4901 Abrupt/rapid climate change;
- PALEOCEANOGRAPHYDE: 4912 Biogeochemical cycles;
- processes;
- and modeling;
- PALEOCEANOGRAPHY