Atlantic Ocean circulation at the last glacial maximum : inferences from data and models

Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2012.

Bibliographic Details
Main Author: Dail, Holly Janine
Other Authors: Carl I. Wunsch.
Format: Thesis
Language:eng
Published: Massachusetts Institute of Technology 2013
Subjects:
Online Access:http://hdl.handle.net/1721.1/78367
_version_ 1811085621560606720
author Dail, Holly Janine
author2 Carl I. Wunsch.
author_facet Carl I. Wunsch.
Dail, Holly Janine
author_sort Dail, Holly Janine
collection MIT
description Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2012.
first_indexed 2024-09-23T13:12:31Z
format Thesis
id mit-1721.1/78367
institution Massachusetts Institute of Technology
language eng
last_indexed 2024-09-23T13:12:31Z
publishDate 2013
publisher Massachusetts Institute of Technology
record_format dspace
spelling mit-1721.1/783672022-01-12T18:17:45Z Atlantic Ocean circulation at the last glacial maximum : inferences from data and models Dail, Holly Janine Carl I. Wunsch. Woods Hole Oceanographic Institution. Joint Program in Oceanography Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences. Woods Hole Oceanographic Institution. Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Joint Program in Oceanography. Earth, Atmospheric, and Planetary Sciences. Woods Hole Oceanographic Institution. Ocean-atmosphere interaction Atlantic Ocean Ocean circulation Atlantic Ocean Mathematical models Paleoceanography Atlantic Ocean Radiative forcing Atlantic Ocean Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2012. This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. Cataloged from student-submitted PDF version of thesis. Includes bibliographical references (p. 221-236). This thesis focuses on ocean circulation and atmospheric forcing in the Atlantic Ocean at the Last Glacial Maximum (LGM, 18-21 thousand years before present). Relative to the pre-industrial climate, LGM atmospheric CO₂ concentrations were about 90 ppm lower, ice sheets were much more extensive, and many regions experienced significantly colder temperatures. In this thesis a novel approach to dynamical reconstruction is applied to make estimates of LGM Atlantic Ocean state that are consistent with these proxy records and with known ocean dynamics. Ocean dynamics are described with the MIT General Circulation Model in an Atlantic configuration extending from 35°S to 75°N at 1° resolution. Six LGM proxy types are used to constrain the model: four compilations of near sea surface temperatures from the MARGO project, as well as benthic isotope records of [delta]¹⁸O and [delta]¹³C compiled by Marchal and Curry; 629 individual proxy records are used. To improve the fit of the model to the data, a least-squares fit is computed using an algorithm based on the model adjoint (the Lagrange multiplier methodology). The adjoint is used to compute improvements to uncertain initial and boundary conditions (the control variables). As compared to previous model-data syntheses of LGM ocean state, this thesis uses a significantly more realistic model of oceanic physics, and is the first to incorporate such a large number and diversity of proxy records. A major finding is that it is possible to find an ocean state that is consistent with all six LGM proxy compilations and with known ocean dynamics, given reasonable uncertainty estimates. Only relatively modest shifts from modern atmospheric forcing are required to fit the LGM data. The estimates presented herein succesfully reproduce regional shifts in conditions at the LGM that have been inferred from proxy records, but which have not been captured in the best available LGM coupled model simulations. In addition, LGM benthic [delta]¹⁸O and [delta]¹³C records are shown to be consistent with a shallow but robust Atlantic meridional overturning cell, although other circulations cannot be excluded. by Holly Janine Dail. Ph.D. 2013-04-12T15:14:34Z 2013-04-12T15:14:34Z 2012 2012 Thesis http://hdl.handle.net/1721.1/78367 834525381 eng M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. http://dspace.mit.edu/handle/1721.1/7582 236 p. application/pdf l------ Massachusetts Institute of Technology
spellingShingle Joint Program in Oceanography.
Earth, Atmospheric, and Planetary Sciences.
Woods Hole Oceanographic Institution.
Ocean-atmosphere interaction Atlantic Ocean
Ocean circulation Atlantic Ocean Mathematical models
Paleoceanography Atlantic Ocean
Radiative forcing Atlantic Ocean
Dail, Holly Janine
Atlantic Ocean circulation at the last glacial maximum : inferences from data and models
title Atlantic Ocean circulation at the last glacial maximum : inferences from data and models
title_full Atlantic Ocean circulation at the last glacial maximum : inferences from data and models
title_fullStr Atlantic Ocean circulation at the last glacial maximum : inferences from data and models
title_full_unstemmed Atlantic Ocean circulation at the last glacial maximum : inferences from data and models
title_short Atlantic Ocean circulation at the last glacial maximum : inferences from data and models
title_sort atlantic ocean circulation at the last glacial maximum inferences from data and models
topic Joint Program in Oceanography.
Earth, Atmospheric, and Planetary Sciences.
Woods Hole Oceanographic Institution.
Ocean-atmosphere interaction Atlantic Ocean
Ocean circulation Atlantic Ocean Mathematical models
Paleoceanography Atlantic Ocean
Radiative forcing Atlantic Ocean
url http://hdl.handle.net/1721.1/78367
work_keys_str_mv AT dailhollyjanine atlanticoceancirculationatthelastglacialmaximuminferencesfromdataandmodels