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Estimating the recharge properties of the deep ocean using noble gases and helium isotopes
Author(s) -
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.
Publication year - 2016
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2016jc011809
Subject(s) - groundwater recharge , meltwater , geology , oceanography , circumpolar deep water , sea ice , ocean gyre , glacial period , ice shelf , deep ocean water , cryosphere , seawater , aquifer , geomorphology , north atlantic deep water , groundwater , thermohaline circulation , subtropics , geotechnical engineering , fishery , biology
The distribution of noble gases and helium isotopes in the dense shelf waters of Antarctica reflects the boundary conditions near the ocean surface: air‐sea exchange, sea ice formation, and subsurface ice melt. We use a nonlinear 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 a distinct contribution from the north Atlantic. The contrast between northern and southern hemisphere recharge properties highlights 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 nonnegligible impact on the atmospheric gas content of Antarctic Bottom Water.