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The role of ocean cooling in setting glacial southern source bottom water salinity

Miller, M. D. and Adkins, J. F. and Menemenlis, D. and Schodlok, M. P. (2012) The role of ocean cooling in setting glacial southern source bottom water salinity. Paleoceanography, 27 (3). Art. No. PA3207. ISSN 0883-8305. https://resolver.caltech.edu/CaltechAUTHORS:20130722-073939346

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Abstract

At the Last Glacial Maximum (LGM), the salinity contrast between northern source deep water and southern source bottom water was reversed with respect to the contrast today. Additionally, Glacial Southern Source Bottom Water (GSSBW) was saltier than Antarctic Bottom Water (AABW), over and above the difference implied by the mean sea level change. This study examines to what extent cold temperatures, through their effect on ice formation and melting, could have caused these differences. Computational sensitivity experiments using a coupled ice shelf cavity–sea ice–ocean model are performed in a Weddell Sea domain, as a representative case study for bottom water formation originating from Antarctic continental shelves. Ocean temperatures at the domain open boundaries are systematically lowered to determine the sensitivity of Weddell Sea water mass properties to a range of cool ocean temperatures. The steady state salinities differ between experiments due to temperature-induced responses of ice shelf and sea ice melting and freezing, evaporation and open boundary fluxes. The results of the experiments indicate that reduced ocean temperature can explain up to 30% of the salinity difference between GSSBW and AABW, primarily due to decreased ice shelf melting. The smallest and most exposed ice shelves, which abut narrow continental shelves, have the greatest sensitivity to the ocean temperature changes, suggesting that at the LGM there could have been a shift in geographical site dominance in bottom water formation. More sea ice is formed and exported in the cold ocean experiments, but the effect of this on salinity is negated by an equal magnitude reduction in evaporation.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1029/2012PA002297 DOIArticle
http://onlinelibrary.wiley.com/doi/10.1029/2012PA002297/abstractPublisherArticle
ORCID:
AuthorORCID
Adkins, J. F.0000-0002-3174-5190
Menemenlis, D.0000-0001-9940-8409
Additional Information:© 2012 American Geophysical Union. Received 23 February 2012; revised 2 May 2012; accepted 20 June 2012; published 4 August 2012. M.D.M. and J.F.A. received funding from the National Science Foundation under NSF grant OCE-0929272. M.D.M., D.M., and M.P.S. received funding from the ECCO2 project, a contribution to the NASA Modeling Analysis and Prediction (MAP) Program. We gratefully acknowledge computational resources and support from the NASA Advanced Supercomputing (NAS) Division. We thank Keith Nicholls for providing the data for Figure 1. Anand Gnanadesikan inspired writing the salt tracer code for analyzing the sources of salinity changes. We are grateful to Martin Losch for his implementation of the ice shelf code in MITgcm and for helpful discussions about ice shelf and sea ice modeling.
Funders:
Funding AgencyGrant Number
NSFOCE-0929272
ECCO2 ProjectUNSPECIFIED
NASA Modeling Analysis and Prediction (MAP) ProgramUNSPECIFIED
Subject Keywords:Antarctic Bottom Water; Last Glacial Maximum; Weddell Sea; ice shelves; salinity; sea ice
Issue or Number:3
Record Number:CaltechAUTHORS:20130722-073939346
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20130722-073939346
Official Citation:Miller, M. D., J. F. Adkins, D. Menemenlis, and M. P. Schodlok (2012), The role of ocean cooling in setting glacial southern source bottom water salinity, Paleoceanography, 27, PA3207, doi:10.1029/2012PA002297
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:39477
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:22 Jul 2013 23:11
Last Modified:09 Mar 2020 13:19

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