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| Titel |
Increasing cloudiness in Arctic damps the increase in phytoplankton primary production due to sea ice receding |
| VerfasserIn |
S. Bélanger, M. Babin, 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 (2013-06-20), S.4087-4101 |
| Datensatznummer |
250018302
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| Publikation (Nr.) |
 copernicus.org/bg-10-4087-2013.pdf |
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| Zusammenfassung |
| The Arctic Ocean and its marginal seas are among the marine regions most affected by climate
change. Here we present the results of a diagnostic model used to assess the
primary production (PP) trends over the 1998–2010 period at pan-Arctic, regional and local (i.e. 9.28 km
resolution) scales. Photosynthetically active radiation (PAR) above and below the sea surface was
estimated using precomputed look-up tables of spectral irradiance, taking as input satellite-derived cloud
optical thickness and cloud fraction parameters from the International Satellite Cloud Climatology
Project (ISCCP) and sea ice concentration from passive microwaves data. A spectrally resolved PP
model, designed for optically complex waters, was then used to assess the PP trends at high spatial resolution.
Results show that PP is rising at a rate of +2.8 TgC yr−1 (or +14% decade−1)
in the circum-Arctic and +5.1 TgC yr−1 when sub-Arctic seas are considered. In contrast, incident
PAR above the sea surface (PAR(0+)) has significantly decreased over the whole
Arctic and sub-Arctic Seas, except over the perennially sea-ice covered waters of the Central
Arctic Ocean. This fading of PAR(0+) (−8% decade−1) was caused by increasing
cloudiness during summer. Meanwhile, PAR penetrating the ocean (PAR(0−)) increased only along the
sea ice margin over the large Arctic continental shelf where sea ice concentration declined
sharply since 1998. Overall, PAR(0−) slightly increased in the circum-Arctic (+3.4% decade−1), while it decreased when considering both Arctic and
sub-Arctic Seas (−3% decade−1). We showed that rising phytoplankton
biomass (i.e. chlorophyll a) normalized by the diffuse attenuation
of photosynthetically usable radiation (PUR), accounted for a larger
proportion of the rise in PP than did the increase in light availability due
to sea-ice loss in several sectors, and particularly in perennially and
seasonally open waters. Against a general backdrop of rising productivity
over Arctic shelves, significant negative PP trends and the timing of
phytoplankton spring-summer bloom were observed in regions known for their
great biological importance such as the coastal polynyas of northern
Greenland. |
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