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Estimating the recharge properties of the deep ocean using noble gases and helium isotopes

Loose, Brice; Jenkins, William J.; Moriarty, Roisin; Brown, Peter; Jullion, Loic; Naveira Garabato, Alberto C.; Torres-valdes, Sinhue; Hoppema, Mario; Ballentine, Chris; Meredith, Michael P.. 2016 Estimating the recharge properties of the deep ocean using noble gases and helium isotopes. Journal of Geophysical Research: Oceans, 121 (8). 5959-5979. https://doi.org/10.1002/2016JC011809

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© Publisher 2016 This is the peer reviewed version of the following article: Loose, Brice, Jenkins, William J., Moriarty, Roisin, Brown, Peter, Jullion, Loic, Naviera Garabato, Alberto C., Torres-Valdes, Sinhue, Hoppema, Mario, Ballentine, Chris and Meredith, Michael P. (2016) Estimating the recharge properties of the deep ocean using noble gases and helium isotopes. Journal of Geophysical Research: Oceans). which has been published in final form at doi:10.1002/2016JC011809). This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.
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Abstract/Summary

The distribution of noble gases and helium isotopes in the dense shelf waters of Antarctica reflect the boundary conditions near the ocean surface: air-sea exchange, sea ice formation and subsurface ice melt. We use a non-linear least-squares solution to determine the value of the recharge temperature and salinity, as well as the excess air injection and glacial meltwater content throughout the water column and in the precursor to Antarctic Bottom Water. The noble gas-derived recharge temperature and salinity in the Weddell Gyre are -1.95 °C and 34.95 psu near 5500 m; these cold, salty recharge values are a result of surface cooling as well as brine rejection during sea ice formation in Antarctic polynyas. In comparison, the global value for deep water recharge temperature is -0.44 °C at 5500 m, which is 1.5 °C warmer than the southern hemisphere deep water recharge temperature, reflecting the contribution from the north Atlantic. The contrast between northern and southern hemisphere recharge properties highlight the impact of sea ice formation on setting the gas properties in southern sourced deep water. Below 1000 m, glacial meltwater averages 3.5 ‰ by volume and represents greater than 50% of the excess neon and argon found in the water column. These results indicate glacial melt has a non-negligible impact on the atmospheric gas content of Antarctic Bottom Water.

Item Type: Publication - Article
Digital Object Identifier (DOI): https://doi.org/10.1002/2016JC011809
Programmes: BAS Programmes > BAS Programmes 2015 > Polar Oceans
ISSN: 2169-9291
Additional Keywords: meridional overturning circulation; glacial meltwater; ocean carbon cycle; Southern Ocean upwelling; sea ice processes
Date made live: 13 Jul 2016 13:16 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/513263

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