Inferring ocean circulation during the last glacial maximum and last deglaciation using data and models

Since the Last Glacial Maximum (LGM, ~ 20,000 years ago) air temperatures warmed, sea level rose roughly 130 meters, and atmospheric concentrations of carbon dioxide increased. This thesis combines global models and paleoceanographic observations to constrain the ocean's role in storing and transporting heat, salt, and other tracers during this time, with implications for understanding how the modem ocean works and how it might change in the future. -- By combining a kinematic ocean model with "upstream" and "downstream" deglacial oxygen isotope time series from benthic and planktonic foraminifera, I show that the data are in agreement with the modem circulation, quantify their power to infer circulation changes, and propose new data locations. -- An ocean general circulation model (the MITgcm) constrained to fit LGM sea surface temperature proxy observations reveals colder ocean temperatures, greater sea ice extent, and changes in ocean mixed layer depth, and suggests that some features in the data are not robust. -- A sensitivity analysis in the MITgcm demonstrates that changes in winds or in ocean turbulent transport can explain the hypothesis that the boundary between deep Atlantic waters originating from Northern and Southern Hemispheres was shallower at the LGM than it is today.

Department dc:contributor.department

Joint Program in Oceanography

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2017

Author dc:creator

• Amrhein, Daniel Edward

Advisor dc:contributor.advisor

• Carl Wunsch.

• Joint Program in Oceanography.
• Earth, Atmospheric, and Planetary Sciences.
• Woods Hole Oceanographic Institution.

Statement dc:rights

• MIT theses are protected by copyright. They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/107085

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/107085