Could Subantarctic Mode Water and Antarctic Intermediate Water play a role in the glacial interglacial variations in atmospheric CO2? A modeling study using NCAR CCSM3 simulations
Abstract
Current studies on glacial and interglacial changes in atmospheric CO2 suggest the importance of the exchange of carbon via deep and bottom waters through changes in the sea ice cover, stratification, and ventilation. Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) could also be an important component affecting the glacial and interglacial variations in atmospheric CO2 . SAMW and AAIW are large-volume intermediate water masses that transport climatically important properties such as, heat, freshwater, and CO2 equatorward into the Southern Hemisphere subtropical gyres. Presently, some of the freshest and coldest SAMW and AAIW are formed in the southeast Pacific. The NCAR CCSM3 LGM simulation (~ 21 kyr) and a LGM hosing simulation of 0.1 Sv of freshwater added to the North Atlantic for 500 years are used in this study. We find SAMW and AAIW during the LGM to be colder, saltier, denser, and significantly younger than the preindustrial (PI) and hosing experiment. SAMW is better ventilated during the LGM. However, for AAIW, increased sea ice cover during the LGM inhibits the atmosphere ocean exchange, thereby, accumulated carbon remains stored within AAIW. Under the hosing experiment, SAMW and AAIW are warmer, fresher, and less dense than the LGM. Sea ice concentration and extent has decreased during the hosing experiment. Therefore, the once isolated AAIW and deep waters are now exposed to the surface potentially leading to the rapid increase in atmospheric CO2 levels as seen during the Heinrich Event 1 and the Younger Dryas. This study suggests that SAMW and AAIW could be an important component for the oceanic uptake and storage of carbon on glacial and interglacial cycles.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFMPP31D..06H
- Keywords:
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- 4901 PALEOCEANOGRAPHY / Abrupt/rapid climate change;
- 4926 PALEOCEANOGRAPHY / Glacial;
- 4928 PALEOCEANOGRAPHY / Global climate models