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Dissolved O2/Ar and other methods reveal rapid changes in productivity during a Lagrangian experiment in the Southern Ocean
Citation
Hamme, RC and Cassar, N and Lance, VP and Vaillancourt, RD and Bender, ML and Strutton, PG and Moore, TS and DeGrandpre, MD and Sabine, CL and Ho, DT and Hargreaves, BR, Dissolved O2/Ar and other methods reveal rapid changes in productivity during a Lagrangian experiment in the Southern Ocean, Journal of Geophysical Research: Oceans, 117, (1) Article C00F12. ISSN 0148-0227 (2012) [Refereed Article]
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Copyright Statement
Copyright 2012 by the American Geophysical Union.
Abstract
We use continuous and discrete measurements of the dissolved O2/Ar ratio in the
mixed layer to investigate the dynamics of biological productivity during the Southern
Ocean Gas Exchange Experiment in March and April 2008. Injections of SF6 defined two
water masses (patches) that were followed for up to 2 weeks. In the first patch,
dissolved O2/Ar was supersaturated, indicating net biological production of organic
carbon. In the second patch, rapidly decreasing O2/Ar could only be reasonably
explained if the mixed layer was experiencing a period of net heterotrophy. The
observations rule out dominant contributions from vertical mixing, lateral dilution, or
respiration in the ship's underway seawater supply lines. We also compare nine different
estimates of net community, new, primary, or gross production made during the
experiment. Net community and new production estimates agreed well in the first patch
but disagreed in the second patch, both during an initial net heterotrophic period but also
during the apparently autotrophic period at the end of the observations. Rapidly changing
productivity during the second patch complicated the comparison of methods that
integrate over daily and several week timescales. Primary productivity values from on-deck
24 h 14C incubations and gross carbon production values from photosynthesis-irradiance
experiments were nearly identical even during highly dynamic periods of net
heterotrophy, while gross oxygen production measurements were 3.5-4.2 times higher
but with uncertainties in that ratio near r+-2. These comparisons show that the
photosynthesis-irradiance experiments based on 1-2 h 14C incubations underestimated
gross carbon production.
Item Details
| Item Type: | Refereed Article |
|---|---|
| Keywords: | southern ocean, productivity measures |
| Research Division: | Earth Sciences |
| Research Group: | Oceanography |
| Research Field: | Biological oceanography |
| Objective Division: | Expanding Knowledge |
| Objective Group: | Expanding knowledge |
| Objective Field: | Expanding knowledge in the earth sciences |
| UTAS Author: | Strutton, PG (Professor Peter Strutton) |
| ID Code: | 80215 |
| Year Published: | 2012 |
| Web of Science® Times Cited: | 65 |
| Deposited By: | IMAS Research and Education Centre |
| Deposited On: | 2012-10-24 |
| Last Modified: | 2022-08-29 |
| Downloads: | 0 |
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