Publikasjoner
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Dunse, Thorben; Dong, Kaixing; Aas, Kjetil Schanke & Stige, Leif Christian
(2022).
Regional-scale phytoplankton dynamics and their association with glacier meltwater runoff in Svalbard.
Biogeosciences.
ISSN 1726-4170.
19,
s. 271–294.
doi:
10.5194/bg-19-271-2022.
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Arctic amplification of global warming has accelerated
mass loss of Arctic land ice over the past decades and
led to increased freshwater discharge into glacier fjords and
adjacent seas. Glacier freshwater discharge is typically associated
with high sediment load which limits the euphotic
depth but may also aid to provide surface waters with essential
nutrients, thus having counteracting effects on marine
productivity. In situ observations from a few measured
fjords across the Arctic indicate that glacier fjords dominated
by marine-terminating glaciers are typically more productive
than those with only land-terminating glaciers. Here
we combine chlorophyll a from satellite ocean color, an indicator
of phytoplankton biomass, with glacier meltwater
runoff from climatic mass-balance modeling to establish a
statistical model of summertime phytoplankton dynamics in
Svalbard (mid-June to September). Statistical analysis reveals
significant and positive spatiotemporal associations of
chlorophyll a with glacier runoff for 7 out of 14 primary
hydrological regions but only within 10 km distance from
the shore. These seven regions consist predominantly of the
major fjord systems of Svalbard. The adjacent land areas
are characterized by a wide range of total glacier coverage
(35.5%to 81.2 %) and fraction of marine-terminating glacier
area (40.2% to 87.4 %). We find that an increase in specific
glacier-runoff rate of 10mm water equivalent per 8 d
period raises summertime chlorophyll a concentrations by
5.2% to 20.0%, depending on the region. During the annual
peak discharge we estimate that glacier runoff increases
chlorophyll a by 13.1% to 50.2% compared to situations
with no runoff. This suggests that glacier runoff is an important
factor sustaining summertime phytoplankton production
in Svalbard fjords, in line with findings from several fjords
in Greenland. In contrast, for regions bordering open coasts,
and beyond 10 km distance from the shore, we do not find
significant associations of chlorophyll a with runoff. In these
regions, physical ocean and sea-ice variables control chlorophyll
a, pointing at the importance of a late sea-ice breakup
in northern Svalbard, as well as the advection of Atlantic water
masses along the West Spitsbergen Current for summertime
phytoplankton dynamics. Our method allows for the investigation
and monitoring of glacier-runoff effects on primary
production throughout the summer season and is applicable
on a pan-Arctic scale, thus complementing valuable
but scarce in situ measurements in both space and time.
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Dunse, Thorben; Dong, Kaixing; Aas, Kjetil Schanke & Stige, Leif Christian
(2021).
Regional-scale phytoplankton dynamics and their association with glacier meltwater runoff in Svalbard.
Biogeosciences Discussions (BGD).
ISSN 1810-6285.
doi:
10.5194/bg-2021-181.
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Publisert
15. feb. 2021 12:05
- Sist endret
15. feb. 2021 12:05