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The significance of the episodic nature of atmospheric deposition to Low Nutrient Low Chlorophyll regions

The significance of the episodic nature of atmospheric deposition to Low Nutrient Low Chlorophyll regions
The significance of the episodic nature of atmospheric deposition to Low Nutrient Low Chlorophyll regions
In the vast Low Nutrient Low-Chlorophyll (LNLC) Ocean, the vertical nutrient supply from the subsurface to the sunlit surface waters is low and atmospheric contribution of nutrients may be one order of magnitude greater over short timescales. The short turnover time of atmospheric Fe and N supply (<1?month for nitrate) further supports deposition being an important source of nutrients in LNLC regions. Yet, the extent to which atmospheric inputs are impacting biological activity and modifying the carbon balance in oligotrophic environments has not been constrained. Here, we quantify and compare the biogeochemical impacts of atmospheric deposition in LNLC regions using both a compilation of experimental data and model outputs. A metadata-analysis of recently conducted field and laboratory bioassay experiments reveals complex responses, and the overall impact is not a simple “fertilization effect” as observed in HNLC regions. Although phytoplankton growth may be enhanced, increases in bacterial activity and respiration result in weakening of biological carbon sequestration. The application of models using climatological or time-averaged non-synoptic deposition rates produced responses that were generally much lower than observed in the bioassay experiments. We demonstrate that experimental data and model outputs show better agreement on short timescale (days to weeks) when strong synoptic pulse of aerosols deposition, similar in magnitude to those observed in the field and introduced in bioassay experiments, is superimposed over the mean atmospheric deposition fields. These results suggest that atmospheric impacts in LNLC regions have been underestimated by models, at least at daily to weekly timescales, as they typically overlook large synoptic variations in atmospheric deposition and associated nutrient and particle inputs. Inclusion of the large synoptic variability of atmospheric input, and improved representation and parameterization of key processes that respond to atmospheric deposition, is required to better constrain impacts in ocean biogeochemical models. This is critical for understanding and prediction of current and future functioning of LNLC regions and their contribution to the global carbon cycle.
aerosol addition, pulse, experimental approach, modeling approach, new nutrients, carbon cycle
0886-6236
1179-1198
Guieu, C.
381151d6-5fff-4839-8217-62b20a254ca5
Aumont, O.
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Paytan, A.
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Bopp, L.
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Law, C.S.
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Mahowald, N.
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Achterberg, E.P.
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Marañón, E.
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Salihoglu, B.
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Crise, A.
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Wagener, T.
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Herut, B.
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Desboeufs, K.
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Kanakidou, M.
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Olgun, N.
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Peters, F.
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Pulido-Villena, E.
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Tovar-Sanchez, A.
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Völker, C.
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Guieu, C.
381151d6-5fff-4839-8217-62b20a254ca5
Aumont, O.
f51d877d-8bb8-4a89-96b0-0eeeda8ea00c
Paytan, A.
a1d03694-22d4-4e4a-acf2-8ffbe3c1fb8a
Bopp, L.
f3ec9518-4c47-471e-9da9-0476aaebdff6
Law, C.S.
0c6a142a-f74d-4d0b-be17-b091432c1e0d
Mahowald, N.
3eb4d13d-5919-48d8-857b-af747294a801
Achterberg, E.P.
685ce961-8c45-4503-9f03-50f6561202b9
Marañón, E.
92f9d2a8-cfe4-4f67-86a1-793af860899a
Salihoglu, B.
ddbc0fd8-8383-41bf-9169-90ed18725b96
Crise, A.
26b85085-c24c-4663-8550-7260ccaa253e
Wagener, T.
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Herut, B.
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Desboeufs, K.
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Kanakidou, M.
bd055b79-a189-45af-81e4-db08ed3de709
Olgun, N.
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Peters, F.
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Pulido-Villena, E.
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Tovar-Sanchez, A.
04060792-6b3f-4f02-bb20-3f062c215956
Völker, C.
e7a71491-b51a-4c9b-84ae-d62a7d2b7a2e

Guieu, C., Aumont, O., Paytan, A., Bopp, L., Law, C.S., Mahowald, N., Achterberg, E.P., Marañón, E., Salihoglu, B., Crise, A., Wagener, T., Herut, B., Desboeufs, K., Kanakidou, M., Olgun, N., Peters, F., Pulido-Villena, E., Tovar-Sanchez, A. and Völker, C. (2014) The significance of the episodic nature of atmospheric deposition to Low Nutrient Low Chlorophyll regions. Global Biogeochemical Cycles, 28 (11), 1179-1198. (doi:10.1002/2014GB004852).

Record type: Article

Abstract

In the vast Low Nutrient Low-Chlorophyll (LNLC) Ocean, the vertical nutrient supply from the subsurface to the sunlit surface waters is low and atmospheric contribution of nutrients may be one order of magnitude greater over short timescales. The short turnover time of atmospheric Fe and N supply (<1?month for nitrate) further supports deposition being an important source of nutrients in LNLC regions. Yet, the extent to which atmospheric inputs are impacting biological activity and modifying the carbon balance in oligotrophic environments has not been constrained. Here, we quantify and compare the biogeochemical impacts of atmospheric deposition in LNLC regions using both a compilation of experimental data and model outputs. A metadata-analysis of recently conducted field and laboratory bioassay experiments reveals complex responses, and the overall impact is not a simple “fertilization effect” as observed in HNLC regions. Although phytoplankton growth may be enhanced, increases in bacterial activity and respiration result in weakening of biological carbon sequestration. The application of models using climatological or time-averaged non-synoptic deposition rates produced responses that were generally much lower than observed in the bioassay experiments. We demonstrate that experimental data and model outputs show better agreement on short timescale (days to weeks) when strong synoptic pulse of aerosols deposition, similar in magnitude to those observed in the field and introduced in bioassay experiments, is superimposed over the mean atmospheric deposition fields. These results suggest that atmospheric impacts in LNLC regions have been underestimated by models, at least at daily to weekly timescales, as they typically overlook large synoptic variations in atmospheric deposition and associated nutrient and particle inputs. Inclusion of the large synoptic variability of atmospheric input, and improved representation and parameterization of key processes that respond to atmospheric deposition, is required to better constrain impacts in ocean biogeochemical models. This is critical for understanding and prediction of current and future functioning of LNLC regions and their contribution to the global carbon cycle.

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e-pub ahead of print date: 2014
Published date: November 2014
Keywords: aerosol addition, pulse, experimental approach, modeling approach, new nutrients, carbon cycle
Organisations: Ocean and Earth Science

Identifiers

Local EPrints ID: 370210
URI: http://eprints.soton.ac.uk/id/eprint/370210
ISSN: 0886-6236
PURE UUID: eb88737b-273b-4a9c-ba75-fed8d46629f8

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Date deposited: 20 Oct 2014 08:32
Last modified: 15 Jul 2019 21:41

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Contributors

Author: C. Guieu
Author: O. Aumont
Author: A. Paytan
Author: L. Bopp
Author: C.S. Law
Author: N. Mahowald
Author: E.P. Achterberg
Author: E. Marañón
Author: B. Salihoglu
Author: A. Crise
Author: T. Wagener
Author: B. Herut
Author: K. Desboeufs
Author: M. Kanakidou
Author: N. Olgun
Author: F. Peters
Author: E. Pulido-Villena
Author: A. Tovar-Sanchez
Author: C. Völker

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