scholarly journals Sensitivity of Phytoplankton Primary Production Estimates to Available Irradiance Under Heterogeneous Sea Ice Conditions

2019 ◽  
Vol 124 (8) ◽  
pp. 5436-5450 ◽  
Author(s):  
Philippe Massicotte ◽  
Ilka Peeken ◽  
Christian Katlein ◽  
Hauke Flores ◽  
Yannick Huot ◽  
...  
Keyword(s):  
Sea Ice ◽  
Primary Production ◽  
Phytoplankton Primary Production ◽  
Ice Conditions

Changes in phytoplankton concentration now drive increased Arctic Ocean primary production

Science ◽  
2020 ◽  
Vol 369 (6500) ◽  
pp. 198-202 ◽  
Author(s):  
K. M. Lewis ◽  
G. L. van Dijken ◽  
K. R. Arrigo
Keyword(s):  
Sea Ice ◽  
Primary Production ◽  
Arctic Ocean ◽  
Open Water ◽  
Water Area ◽  
The Arctic ◽  
Carbon Export ◽  
Phytoplankton Primary Production ◽  
Open Water Area ◽  
The Arctic Ocean

Historically, sea ice loss in the Arctic Ocean has promoted increased phytoplankton primary production because of the greater open water area and a longer growing season. However, debate remains about whether primary production will continue to rise should sea ice decline further. Using an ocean color algorithm parameterized for the Arctic Ocean, we show that primary production increased by 57% between 1998 and 2018. Surprisingly, whereas increases were due to widespread sea ice loss during the first decade, the subsequent rise in primary production was driven primarily by increased phytoplankton biomass, which was likely sustained by an influx of new nutrients. This suggests a future Arctic Ocean that can support higher trophic-level production and additional carbon export.

scholarly journals Deep-sea benthic communities and oxygen fluxes in the Arctic Fram Strait controlled by sea-ice cover and water depth

2018 ◽  
Author(s):  
Ralf Hoffmann ◽  
Ulrike Braeckman ◽  
Christiane Hasemann ◽  
Frank Wenzhöfer
Keyword(s):  
Sea Ice ◽  
Primary Production ◽  
Water Depth ◽  
Deep Sea ◽  
Abiotic Factors ◽  
Fram Strait ◽  
Sea Ice Concentration ◽  
Covered Area ◽  
Ice Concentration ◽  
Ice Conditions

Abstract. Arctic Ocean surface sea-ice conditions are linked with the deep sea benthic oxygen fluxes via a cascade of dependencies across ecosystem components like primary production, food supply, the activity of the benthic community, and their functions. Additionally, each of the ecosystem components is influenced by abiotic factors like light availability, temperature, water depth or grain size structure. In this study, we investigated the coupling between surface sea-ice conditions and deep-sea benthic remineralization processes through a cascade of dependencies in the Fram Strait. We measured sea-ice concentrations, nutrient profiles, different sediment compounds, benthic community parameters, and oxygen fluxes at 12 stations in the HAUSGARTEN area of the Fram Strait in water depth between 275–2500 m. Our investigations reveal that the Fram Strait is bisected in a permanently and highly sea-ice covered area and a seasonally and low sea-ice covered area, which both are long-lasting and stable. Within the Fram Strait ecosystem, sea-ice concentration and water depth are two independent abiotic factors, controlling the deep-sea benthos. Sea-ice concentration correlates well with the available food, water depth with the oxygen flux, and both abiotic factors correlate with the macrofauna biomass. However, in water depths >1500 m the influence of the surface sea-ice cover fades out and water depth effect becomes more dominant. Remineralisation across the Fram Strait is ~ 1 mmol C m−2 d−1. Owing to the contrasting primary production pattern, our data indicate that the portion of newly produced carbon that is remineralised by the benthos is ~2.6 % in the seasonally low sea-ice covered Fram Strait but can be >15 % in the permanently high sea-ice covered Fram Strait. Furthermore, by comparing a permanently sea-ice covered area with a seasonally sea-ice covered area, we discuss a potential scenario for the deep-sea benthic ecosystem in the future Arctic Ocean, in which an increased surface primary production can lead to increasing benthic remineralisation in water depths <1500 m.

scholarly journals Subglacial upwelling in winter/spring increases under-ice primary production

2020 ◽  
Author(s):  
Tobias Reiner Vonnahme ◽  
Emma Persson ◽  
Ulrike Dietrich ◽  
Eva Hejdukova ◽  
Christine Dybwad ◽  
...  
Keyword(s):  
Surface Layer ◽  
Sea Ice ◽  
Primary Production ◽  
Reference Site ◽  
Outlet Glacier ◽  
Substantial Impact ◽  
Phytoplankton Primary Production ◽  
Glacier Front ◽  
Bulk Salinity ◽  
Fast Ice

Abstract. Subglacial upwelling of nutrient rich bottom water is known to support high summer primary production in Arctic fjord systems. However, during the winter/spring season, the importance of subglacial upwelling has not been considered yet. We hypothesized that subglacial upwelling under sea ice is present in winter/spring and sufficient to increase phytoplankton primary productivity. We evaluated the effects of the subglacial upwelling on primary production in a seasonally fast ice covered Svalbard fjord (Billefjorden) influenced by a tidewater outlet glacier in April/May 2019. We found clear evidence for subglacial upwelling. Although the estimated entrainment factor (1.6) and total fluxes were lower than in summer studies, we observed substantial impact on the fjord ecosystem and primary production. The subglacial meltwater leads to a salinity stratified surface layer and sea ice formation with low bulk salinity and permeability. The combination of the stratified surface layer, a two-fold higher under-ice irradiance, and higher N and Si concentrations at the glacier front supported two orders of magnitude higher primary production (42.6 mg C m−2 d−1) compared to a marine reference site at the fast ice edge. The nutrient supply increased primary production by approximately 30 %. The brackish water sea ice at the glacier front with its low bulk salinity contained a reduced brine volume, limiting the inhabitable place and nutrient exchange with the underlying seawater compared to full marine sea ice. Microbial and algal communities were substantially different in subglacial influenced water and sea ice compared to the marine reference site, sharing taxa with the subglacial outflow water. We suggest that with climate change, the retreat of tidewater glaciers could lead to decreased under-ice phytoplankton primary production, while sea ice algae production and biomass may become increasingly important.

scholarly journals Early spring subglacial discharge plumes fuel under-ice primary production at a Svalbard tidewater glacier

2021 ◽  
Vol 15 (4) ◽  
pp. 2083-2107
Author(s):  
Tobias Reiner Vonnahme ◽  
Emma Persson ◽  
Ulrike Dietrich ◽  
Eva Hejdukova ◽  
Christine Dybwad ◽  
...  
Keyword(s):  
Sea Ice ◽  
Primary Production ◽  
Bottom Water ◽  
Reference Site ◽  
Early Spring ◽  
Phytoplankton Primary Production ◽  
Tidewater Glacier ◽  
Glacier Front ◽  
Bulk Salinity ◽  
Fast Ice

Abstract. Subglacial upwelling of nutrient-rich bottom water is known to sustain elevated summer primary production in tidewater-glacier-influenced fjord systems. However, the importance of subglacial upwelling during the early spring season has not been considered yet. We hypothesized that subglacial discharge under sea ice is present in early spring and that its flux is sufficient to increase phytoplankton primary productivity. We evaluated the effects of the submarine discharge on primary production in a seasonally fast-ice covered Svalbard fjord (Billefjorden) influenced by a tidewater outlet glacier in April and May 2019. We found clear evidence for subglacial discharge and upwelling. Although the estimated bottom-water entrainment factor (1.6) and total fluxes were lower than in summer studies, we still observed substantial impact on the fjord ecosystem and primary production at this time of the year. The subglacial discharge leads to a salinity-stratified surface water layer and sea ice formation with low bulk salinity and permeability. The combination of the stratified surface layer, a 2-fold higher under-ice irradiance due to thinner snow cover, and higher N and Si concentrations at the glacier front supported phytoplankton primary production 2 orders of magnitude higher (42.6 mg C m−2 d−1) compared to a marine reference site at the fast-ice edge. Reciprocal transplant experiments showed that nutrient supply increased phytoplankton primary production by approximately 30 %. The brackish-water sea ice at the glacier front with its low bulk salinity contained a reduced brine volume, limiting the inhabitable brine channel space and nutrient exchange with the underlying seawater compared to full marine sea ice. Microbial and algal communities were substantially different in subglacial-influenced water and sea ice compared to the marine reference site, sharing taxa with the subglacial outflow water. We suggest that with climate change, the retreat of tidewater glaciers in early spring could lead to decreased under-ice phytoplankton primary production. In contrast, sea ice algae production and biomass may become increasingly important, unless sea ice disappears first, in which case spring phytoplankton primary production may increase.

scholarly journals Increasing cloudiness in Arctic damps the increase in phytoplankton primary production due to sea ice receding

2012 ◽  
Vol 9 (10) ◽  
pp. 13987-14012 ◽  
Author(s):  
S. Bélanger ◽  
M. Babin ◽  
J.-E. Tremblay
Keyword(s):  
Sea Ice ◽  
Primary Production ◽  
Arctic Ocean ◽  
Sea Surface ◽  
The Arctic ◽  
Diagnostic Model ◽  
Arctic Seas ◽  
Sea Ice Concentration ◽  
Phytoplankton Primary Production ◽  
Ice Concentration

Abstract. 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 elucidate the main drivers of primary production (PP) trends over the 1998–2010 period at pan-Arctic 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 and 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 produce maps of PP trends. Results show that incident PAR above the sea surface (PAR(0+)) has significantly decreased over the whole Arctic and sub-Arctic Seas, except over the perrennially sea ice covered waters of the Central Arctic Ocean. This fading of PAR(0+) (+8% decade–1) was caused by increasing cloudiness May and June. 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) by phytoplankton 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 perrennially and seasonally open waters. Against a general backdrop of rising productivity over Arctic shelves, significant negative trends were observed in regions known for their great biological importance such as the coastal polynyas of Northern Greenland.

scholarly journals Increasing cloudiness in Arctic damps the increase in phytoplankton primary production due to sea ice receding

2013 ◽  
Vol 10 (6) ◽  
pp. 4087-4101 ◽  
Author(s):  
S. Bélanger ◽  
M. Babin ◽  
J.-É. Tremblay
Keyword(s):  
Sea Ice ◽  
Primary Production ◽  
Arctic Ocean ◽  
Sea Surface ◽  
The Arctic ◽  
Diagnostic Model ◽  
Arctic Seas ◽  
Sea Ice Concentration ◽  
Phytoplankton Primary Production ◽  
Ice Concentration

Abstract. 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.

Prévoir les variations saisonnières de la glace de mer arctique et leurs impacts sur le climat

2020 ◽  
pp. 024
Author(s):  
Rym Msadek ◽  
Gilles Garric ◽  
Sara Fleury ◽  
Florent Garnier ◽  
Lauriane Batté ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Region ◽  
Arctic Sea Ice ◽  
Climate Impacts ◽  
The Arctic ◽  
Recent Effort ◽  
Sea Ice Thickness ◽  
Arctic Sea ◽  
Ice Conditions ◽  
Upper Level

L'Arctique est la région du globe qui s'est réchauffée le plus vite au cours des trente dernières années, avec une augmentation de la température de surface environ deux fois plus rapide que pour la moyenne globale. Le déclin de la banquise arctique observé depuis le début de l'ère satellitaire et attribué principalement à l'augmentation de la concentration des gaz à effet de serre aurait joué un rôle important dans cette amplification des températures au pôle. Cette fonte importante des glaces arctiques, qui devrait s'accélérer dans les décennies à venir, pourrait modifier les vents en haute altitude et potentiellement avoir un impact sur le climat des moyennes latitudes. L'étendue de la banquise arctique varie considérablement d'une saison à l'autre, d'une année à l'autre, d'une décennie à l'autre. Améliorer notre capacité à prévoir ces variations nécessite de comprendre, observer et modéliser les interactions entre la banquise et les autres composantes du système Terre, telles que l'océan, l'atmosphère ou la biosphère, à différentes échelles de temps. La réalisation de prévisions saisonnières de la banquise arctique est très récente comparée aux prévisions du temps ou aux prévisions saisonnières de paramètres météorologiques (température, précipitation). Les résultats ayant émergé au cours des dix dernières années mettent en évidence l'importance des observations de l'épaisseur de la glace de mer pour prévoir l'évolution de la banquise estivale plusieurs mois à l'avance. Surface temperatures over the Arctic region have been increasing twice as fast as global mean temperatures, a phenomenon known as arctic amplification. One main contributor to this polar warming is the large decline of Arctic sea ice observed since the beginning of satellite observations, which has been attributed to the increase of greenhouse gases. The acceleration of Arctic sea ice loss that is projected for the coming decades could modify the upper level atmospheric circulation yielding climate impacts up to the mid-latitudes. There is considerable variability in the spatial extent of ice cover on seasonal, interannual and decadal time scales. Better understanding, observing and modelling the interactions between sea ice and the other components of the climate system is key for improved predictions of Arctic sea ice in the future. Running operational-like seasonal predictions of Arctic sea ice is a quite recent effort compared to weather predictions or seasonal predictions of atmospheric fields like temperature or precipitation. Recent results stress the importance of sea ice thickness observations to improve seasonal predictions of Arctic sea ice conditions during summer.

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