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

journal contribution
posted on 2023-05-17, 06:29 authored by DiFiore, PJ, Sigman, DM, Karsh, K, Trull, T, Dunbar, RB, Robinson, RS
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.

History

Publication title

Geophysical Research Letters

Volume

37

Issue

17

Article number

L17601

Number

L17601

Pagination

1-5

ISSN

0094-8276

Department/School

School of Natural Sciences

Publisher

Amer Geophysical Union

Place of publication

2000 Florida Ave Nw, Washington, USA, Dc, 20009

Rights statement

Copyright 2010 American Geophysical Union

Repository Status

  • Restricted

Socio-economic Objectives

Measurement and assessment of marine water quality and condition

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