The future of the subsurface chlorophyll-a maximum in the Canada Basin-A model intercomparison
The future of the subsurface chlorophyll-a maximum in the Canada Basin-A model intercomparison
Six Earth system models and three ocean-ice-ecosystem models are analyzed to evaluate magnitude and depth of the subsurface Chl-a maximum (SCM) in the Canada Basin and ratio of surface to subsurface Chl-a in a future climate scenario. Differences in simulated Chl-a are caused by large intermodel differences in available nitrate in the Arctic Ocean and to some extent by ecosystem complexity. Most models reproduce the observed SCM and nitracline deepening and indicate a continued deepening in the future until the models reach a new state with seasonal ice-free waters. Models not representing a SCM show either too much nitrate and hence no surface limitation or too little nitrate with limited surface growth only. The models suggest that suppression of the nitracline and deepening of the SCM are caused by enhanced stratification, likely driven by enhanced Ekman convergence and freshwater contributions with primarily large-scale atmospheric driving mechanisms. The simulated ratio of near-surface Chl-a to depth-integrated Chl-a is slightly decreasing in most areas of the Arctic Ocean due to enhanced contributions of subsurface Chl-a. Exceptions are some shelf areas and regions where the continued ice thinning leaves winter ice too thin to provide a barrier to momentum fluxes, allowing winter mixing to break up the strong stratification. Results confirm that algorithms determining vertically integrated Chl-a from surface Chl-a need to be tuned to Arctic conditions, but likely require little or no adjustments in the future.
Arctic Ocean, deep chlorophyll maximum, Canada Basin, Chl-a profile
387-409
Steiner, N.S.
43c590dd-9e02-4aa3-9429-e3049d8a9413
Sou, T.
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Deal, C.
cd8c4998-c45a-47fa-ba22-4921ca72c92a
Jackson, J.M.
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Jin, M.
135d1c5a-6ea9-4230-b648-f91f5b1274f0
Popova, E.
3ea572bd-f37d-4777-894b-b0d86f735820
Williams, W.
35cc0979-e4c5-4438-a7bb-10d1fd5653d0
Yool, A.
882aeb0d-dda0-405e-844c-65b68cce5017
11 January 2016
Steiner, N.S.
43c590dd-9e02-4aa3-9429-e3049d8a9413
Sou, T.
a754dea9-03cb-45c3-b163-03c415eadabb
Deal, C.
cd8c4998-c45a-47fa-ba22-4921ca72c92a
Jackson, J.M.
56d28442-62b1-4425-96c6-27c321dfd310
Jin, M.
135d1c5a-6ea9-4230-b648-f91f5b1274f0
Popova, E.
3ea572bd-f37d-4777-894b-b0d86f735820
Williams, W.
35cc0979-e4c5-4438-a7bb-10d1fd5653d0
Yool, A.
882aeb0d-dda0-405e-844c-65b68cce5017
Steiner, N.S., Sou, T., Deal, C., Jackson, J.M., Jin, M., Popova, E., Williams, W. and Yool, A.
(2016)
The future of the subsurface chlorophyll-a maximum in the Canada Basin-A model intercomparison.
Journal of Geophysical Research: Oceans, 121 (1), .
(doi:10.1002/2015JC011232).
Abstract
Six Earth system models and three ocean-ice-ecosystem models are analyzed to evaluate magnitude and depth of the subsurface Chl-a maximum (SCM) in the Canada Basin and ratio of surface to subsurface Chl-a in a future climate scenario. Differences in simulated Chl-a are caused by large intermodel differences in available nitrate in the Arctic Ocean and to some extent by ecosystem complexity. Most models reproduce the observed SCM and nitracline deepening and indicate a continued deepening in the future until the models reach a new state with seasonal ice-free waters. Models not representing a SCM show either too much nitrate and hence no surface limitation or too little nitrate with limited surface growth only. The models suggest that suppression of the nitracline and deepening of the SCM are caused by enhanced stratification, likely driven by enhanced Ekman convergence and freshwater contributions with primarily large-scale atmospheric driving mechanisms. The simulated ratio of near-surface Chl-a to depth-integrated Chl-a is slightly decreasing in most areas of the Arctic Ocean due to enhanced contributions of subsurface Chl-a. Exceptions are some shelf areas and regions where the continued ice thinning leaves winter ice too thin to provide a barrier to momentum fluxes, allowing winter mixing to break up the strong stratification. Results confirm that algorithms determining vertically integrated Chl-a from surface Chl-a need to be tuned to Arctic conditions, but likely require little or no adjustments in the future.
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Accepted/In Press date: 8 December 2015
Published date: 11 January 2016
Keywords:
Arctic Ocean, deep chlorophyll maximum, Canada Basin, Chl-a profile
Organisations:
Marine Systems Modelling
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Local EPrints ID: 397962
URI: http://eprints.soton.ac.uk/id/eprint/397962
PURE UUID: e3f0691d-c425-4475-b182-678c981b604a
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Date deposited: 12 Jul 2016 12:56
Last modified: 15 Mar 2024 01:25
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Author:
N.S. Steiner
Author:
T. Sou
Author:
C. Deal
Author:
J.M. Jackson
Author:
M. Jin
Author:
E. Popova
Author:
W. Williams
Author:
A. Yool
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