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Poleward decrease in the isotope effect of nitrate assimilation across the Southern Ocean


DiFiore, PJ and Sigman, DM and Karsh, K and Trull, T and Dunbar, RB and Robinson, RS, Poleward decrease in the isotope effect of nitrate assimilation across the Southern Ocean, Geophysical Research Letters, 37, (17) Article L17601. ISSN 0094-8276 (2010) [Refereed Article]

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Copyright Statement

Copyright 2010 American Geophysical Union

DOI: doi:10.1029/2010GL044090


Recent studies provide seasonally and spatially resolved information on the isotopic characteristics of nitrate supply and N cycling in Southern Ocean surface waters. The new data improve our understanding of the nitrate supply to the Antarctic surface and its isotopic characteristics, especially with regard to the summertime subsurface minimum temperature (Tmin) layer in the Antarctic. We use these findings to update and compile estimates of the N isotope effect of nitrate assimilation, ε, in the Southern Ocean near Australia. A poleward decrease in ε emerges, from 8-9‰ in the Subantarctic Zone (SAZ, 40-52°S) to similar to 5‰ in the Polar Antarctic Zone (PAZ, ~66°S). ε is strongly correlated with mixed layer depth at the time of sampling. We hypothesize that the correlation is driven by the physiological response of diatoms to light availability, with light limitation leading to higher cellular efflux of nitrate and thus higher ε.

Item Details

Item Type:Refereed Article
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Chemical oceanography
Objective Division:Environmental Management
Objective Group:Marine systems and management
Objective Field:Measurement and assessment of marine water quality and condition
UTAS Author:Karsh, K (Dr Kristen Karsh)
UTAS Author:Trull, T (Professor Thomas Trull)
ID Code:70487
Year Published:2010
Web of Science® Times Cited:41
Deposited By:Research Division
Deposited On:2011-06-23
Last Modified:2014-12-08

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