Publication Abstracts

Sheth 1999

Sheth, S., 1999: Ocean Circulation Changes and Greenhouse Warming Predicted by Coupled GCMs. Ph.D. thesis. Columbia University.

This thesis presents the results of several general circulation model simulations aimed at studying the effect of ocean circulation changes when they occur in conjunction with increased atmospheric trace gas concentrations. An atmospheric general circulation model coupled to a simple mixed layer ocean was forced with altered implied ocean heat transports during a period of increasing trace gases. A 20% increase in transports led to enhanced warming in the circum-North Atlantic region. While an equivalent decrease did not mitigate the warming caused by the increased trace gases, its magnitude was less than in a simulation with unaltered ocean heat transports. Significant changes in ice cover and the moisture balance were seen, consistent with the feedbacks believed to be associated with ocean heat transport changes. Subsequently I used a coupled ocean-atmosphere model to allow for the full range of feedbacks. Sensitivity studies were made to improve the simulation of high latitude temperature and hydrology and thus the thermohaline circulation, an important aspect of the ocean's role in climate. Improved sea ice parameterisations and a mixing scheme that included the effect of the mechanical stirring by winds in the creation of the mixed layer resulted in control climates that better matched salinity and temperature observations. Additional simulations used a hierarchy of coupled ocean- atmosphere models combining different atmosphere and ocean components. Major differences in simulated surface salinities had a significant impact on the calculated poleward heat transports. In response to increased trace gases, all replicated the qualitative response seen in other coupled ocean-atmosphere models: greater warming over land than ocean and maximum warming at high northern latitudes in winter. Some had regions of minimum warming in the North Atlantic and Ross Sea due to positive feedbacks: a local effect on convection in the Ross Sea and a non-local impact on the meridional circulation in the North Atlantic. A decrease of between 8-33% is seen in the poleward transport of heat at the doubling of CO2. The greatest decrease was seen in experiments with minimal control run drift in surface salinity and temperature. Results from simulations that had drift were more difficult to interpret.

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BibTeX Citation

@phdthesis{sh09200l,
  author={Sheth, S.},
  title={Ocean Circulation Changes and Greenhouse Warming Predicted by Coupled GCMs},
  year={1999},
  school={Columbia University},
  address={New York, N.Y.},
}

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RIS Citation

TY  - THES
ID  - sh09200l
AU  - Sheth, S.
PY  - 1999
BT  - Ocean Circulation Changes and Greenhouse Warming Predicted by Coupled GCMs
PB  - Columbia University
CY  - New York, N.Y.
ER  -

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