Continuous shipboard measurements of oceanic δ^18O, δD and δ^13C(DIC) along a transect from New Zealand to Antarctica using cavity ring-down isotope spectrometry

Bass, Adrian M., Munksgaard, Niels C., O'Grady, Damien, Williams, Michael J.M., Bostock, Helen C., Rintoul, Stephen R., and Bird, Michael I. (2014) Continuous shipboard measurements of oceanic δ^18O, δD and δ^13C(DIC) along a transect from New Zealand to Antarctica using cavity ring-down isotope spectrometry. Journal of Marine Systems, 137. pp. 21-27.

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Abstract

Cavity ring-down spectrometers, with automated sampling interfaces, were deployed to allow measurements of water isotopes (δ^18O, δD) and dissolved inorganic carbon (δ^13(CDIC)) stable isotope ratios at high temporal resolution along a transect from New Zealand to the Antarctic continental shelf. Measurements every 10 min for δ^18O and δD, 15 min for DIC yielded 2499 and 2289 discrete measurements respectively. High resolution data enabled the delineation of water mass boundaries as well as revealing insights into surface hydrological and biological processes. δ^18O, δD, and δ^13(CDIC) decreased southwards, dropping by approximately 1.0‰, 7.0‰, and 0.5‰, respectively. Though the decline in δ^13(CDIC) with latitude was generally linear, the drop in δ^18O and δD was punctuated by areas of rapid, significant change corresponding to the Sub-Tropical, Sub-Antarctic and Polar Fronts. North of the Sub-Antarctic Front (approx. 54.5°S) the dominant control on water and DIC isotopes was the precipitation–evaporation balance and the contribution of upwelling waters, respectively. Further south, in close proximity to the sea ice and on the Antarctic shelf, water isotope values were more variable and predominantly influenced by the melting/freezing of sea-ice coupled to inputs from glacial/snow melt water. Local increases in δ^13(CDIC) were likely due to photosynthetic enrichment of the DIC pool. Using this new instrumentation has provided one of the most comprehensive oceanic transect data sets yet achieved and illustrates the potential of these methods to delineate discrete water masses and advance our knowledge of both water and inorganic carbon cycling processes in the ocean. This methodology, combining high-resolution isotopic measurements with hydrographic data, has significant benefits in modelling water mixing in locations with multiple sources and controlling processes.

Item ID: 38443
Item Type: Article (Research - C1)
ISSN: 0924-7963
Keywords: oxygen isotopes; hydrogen isotopes; dissolved inorganic carbon; Antarctica; sea-ice; southern ocean; polar front; sub-tropical front; sub-Antarctic front
Funders: Australian Government Cooperative Research Centre Program, Australian Government Deparment of the Environment, Bureau of Meteorology, CSIRO Australian Climate Change Science Program, National Institute of Water and Atmospheric Research (NIWA), Australian Research Council (ARC)
Projects and Grants: NIWA COPR1304, NIWA CLCS1301, ARC grant LE130100159
Date Deposited: 27 Apr 2015 23:19
FoR Codes: 04 EARTH SCIENCES > 0405 Oceanography > 040599 Oceanography not elsewhere classified @ 33%
04 EARTH SCIENCES > 0402 Geochemistry > 040299 Geochemistry not elsewhere classified @ 33%
03 CHEMICAL SCIENCES > 0399 Other Chemical Sciences > 039901 Environmental Chemistry (incl Atmospheric Chemistry) @ 34%
SEO Codes: 96 ENVIRONMENT > 9611 Physical and Chemical Conditions of Water > 961104 Physical and Chemical Conditions of Water in Marine Environments @ 100%
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