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| Titel |
Parameterization of vertical chlorophyll a in the Arctic Ocean: impact of the subsurface chlorophyll maximum on regional, seasonal, and annual primary production estimates |
| VerfasserIn |
M. Ardyna, M. Babin, M. Gosselin, E. Devred, S. Bélanger, A. Matsuoka, J.-É. Tremblay |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 6 ; Nr. 10, no. 6 (2013-06-28), S.4383-4404 |
| Datensatznummer |
250018319
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| Publikation (Nr.) |
 copernicus.org/bg-10-4383-2013.pdf |
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| Zusammenfassung |
| Predicting water-column phytoplankton biomass from near-surface measurements
is a common approach in biological oceanography, particularly since the
advent of satellite remote sensing of ocean color (OC). In the Arctic Ocean,
deep subsurface chlorophyll maxima (SCMs) that significantly contribute to
primary production (PP) are often observed. These are neither detected by
ocean color sensors nor accounted for in the primary production models
applied to the Arctic Ocean. Here, we assemble a large database of pan-Arctic
observations (i.e., 5206 stations) and develop an empirical model to estimate
vertical chlorophyll a (Chl a) according to (1) the shelf–offshore
gradient delimited by the 50 m isobath, (2) seasonal variability along
pre-bloom, post-bloom, and winter periods, and (3) regional differences
across ten sub-Arctic and Arctic seas. Our detailed analysis of the dataset
shows that, for the pre-bloom and winter periods, as well as for high surface
Chl a concentration (Chl asurf; 0.7–30 mg m−3)
throughout the open water period, the Chl a maximum is mainly located at or
near the surface. Deep SCMs occur chiefly during the post-bloom period when
Chl asurf is low (0–0.5 mg m−3). By applying our empirical
model to annual Chl asurf time series, instead of the
conventional method assuming vertically homogenous Chl a, we produce novel
pan-Arctic PP estimates and associated uncertainties. Our results show that
vertical variations in Chl a have a limited impact on annual
depth-integrated PP. Small overestimates found when SCMs are shallow
(i.e., pre-bloom, post-bloom > 0.7 mg m−3, and the winter period)
somehow compensate for the underestimates found when SCMs are deep
(i.e., post-bloom < 0.5 mg m−3). SCMs are, however, important
seasonal features with a substantial impact on depth-integrated PP estimates,
especially when surface nitrate is exhausted in the Arctic Ocean and where
highly stratified and oligotrophic conditions prevail. |
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