Reconstructing paleosalinity from δ18O: Coupled model simulations of the Last Glacial Maximum, Last Interglacial and Late Holocene

Holloway, Max D. ORCID: https://orcid.org/0000-0003-0709-3644; Sime, Louise C. ORCID: https://orcid.org/0000-0002-9093-7926; Singarayer, Joy S.; Tindall, Julia C.; Valdes, Paul J.. 2016 Reconstructing paleosalinity from δ18O: Coupled model simulations of the Last Glacial Maximum, Last Interglacial and Late Holocene. Quaternary Science Reviews, 131 (B). 350-364. https://doi.org/10.1016/j.quascirev.2015.07.007

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Abstract/Summary

Reconstructions of salinity are used to diagnose changes in the hydrological cycle and ocean circulation. A widely used method of determining past salinity uses oxygen isotope (δOw) residuals after the extraction of the global ice volume and temperature components. This method relies on a constant relationship between δOw and salinity throughout time. Here we use the isotope-enabled fully coupled General Circulation Model (GCM) HadCM3 to test the application of spatially and time-independent relationships in the reconstruction of past ocean salinity. Simulations of the Late Holocene (LH), Last Glacial Maximum (LGM), and Last Interglacial (LIG) climates are performed and benchmarked against existing compilations of stable oxygen isotopes in carbonates (δOc), which primarily reflect δOw and temperature. We find that HadCM3 produces an accurate representation of the surface ocean δOc distribution for the LH and LGM. Our simulations show considerable variability in spatial and temporal δOw-salinity relationships. Spatial gradients are generally shallower but within ∼50% of the actual simulated LH to LGM and LH to LIG temporal gradients and temporal gradients calculated from multi-decadal variability are generally shallower than both spatial and actual simulated gradients. The largest sources of uncertainty in salinity reconstructions are found to be caused by changes in regional freshwater budgets, ocean circulation, and sea ice regimes. These can cause errors in salinity estimates exceeding 4 psu. Our results suggest that paleosalinity reconstructions in the South Atlantic, Indian and Tropical Pacific Oceans should be most robust, since these regions exhibit relatively constant δOw-salinity relationships across spatial and temporal scales. Largest uncertainties will affect North Atlantic and high latitude paleosalinity reconstructions. Finally, the results show that it is difficult to generate reliable salinity estimates for regions of dynamic oceanography, such as the North Atlantic, without additional constraints.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1016/j.quascirev.2015.07.007
Programmes:	BAS Programmes > BAS Programmes 2015 > Ice Dynamics and Palaeoclimate
ISSN:	02773791
Additional Keywords:	paleosalinity, isotopes, oxygen-18, Last Glacial Maximum, Last Interglacial, paleoceanography
Date made live:	28 Jul 2015 10:46 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/511381

Item Type:

Publication - Article

Digital Object Identifier (DOI):

https://doi.org/10.1016/j.quascirev.2015.07.007

Programmes:

BAS Programmes > BAS Programmes 2015 > Ice Dynamics and Palaeoclimate

ISSN:

02773791

Additional Keywords:

paleosalinity, isotopes, oxygen-18, Last Glacial Maximum, Last Interglacial, paleoceanography

Date made live:

28 Jul 2015 10:46 +0 (UTC)