Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published August 4, 2012 | Supplemental Material + Published
Journal Article Open

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

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.

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.

Attached Files

Published - palo1785.pdf

Supplemental Material - palo1785-sup-0001-t01.txt

Files

palo1785.pdf
Files (1.6 MB)
Name Size Download all
md5:c35fb4d8d57d647433de1ca86adaf56b
1.6 MB Preview Download
md5:e693c6943b1e81e75a11c17c1b450fef
2.6 kB Preview Download

Additional details

Created:
August 22, 2023
Modified:
October 24, 2023