These two observatories help to establish a network of observatories across the Arctic, which is ... more These two observatories help to establish a network of observatories across the Arctic, which is funded through the NSF Arctic Observatory Network (AON) program. The other flux stations that participate in this network are located near Abisko, Sweden and Zackenberg, Greenland, as well as a series of sites across Arctic Canada. The goal of making flux measurements made at these sites is to: 1) quantify and understand the controls of carbon, water, and energy exchange at each site, 2) permit cross-site synthesis of the carbon, water, and energy fluxes across the representative terrestrial ecosystems in the Arctic, and 3) parameterize and validate ecosystem and land-surface FluxLetter The Newsletter of FLUXNET
Antarctic sea ice is a seasonal source of iron (Fe) to the Southern Ocean (SO), where surface wat... more Antarctic sea ice is a seasonal source of iron (Fe) to the Southern Ocean (SO), where surface waters Fe levels are otherwise generally low. The effectiveness of Fe released from melting sea ice does not only depends on the magnitude of the supply, but also on the biological Fe demand. Here, we hypothesize that Fe uptake rates by sea-ice algae and under-ice phytoplankton are higher than the rates reported for open ocean phytoplankton in the SO. We performed 55Fe and carbon (14C) short-term uptake field measurements in, on and under Antarctic sea ice. Our results show that over 90% of Fe taken up by sea-ice algae and under-ice phytoplankton was found on the outside of the algal cells. The intracellular Fe (Feintra) uptake rates were high and reached up 68, 194 and 203 pmol Fe L− 1 d− 1 in seawater, bottom ice and over-ice respectively. Overall C uptake in bottom sea ice was low, ranging between 0.03 and 3.2 µmol C L− 1 d− 1, but similar to previous sea-ice studies. The Feintra:C ratio...
While representing less than 5% of the total ice cover around Antarctica, landfast sea ice is nev... more While representing less than 5% of the total ice cover around Antarctica, landfast sea ice is nevertheless an important habitat known to exhibit high biomass levels at the ocean/ice interface, with particulate organic carbon (POC) concentrations easily reaching 2000 μmol C L–1 during spring bloom. Surprisingly, together with the POC increase in bottom ice, fieldwork measurements performed in East Antarctica (Adélie Land 2011, McMurdo Sound 2012, Prydz Bay 2015) of nitrate and phosphate concentrations report a simultaneous increase with concentrations exceeding those of underlying seawater, suggesting an intense remineralization and nitrification processes within the ice. This goes against the classic view of nutrients being consumed during the growth season and regenerated after the height of the bloom. Regardless of the high nitrate levels available in the ice, increasing total nitrogen concentrations also suggest still more nitrogen from the underlying seawater was brought into the ice. Results of a NPZD-model indicates that a second nutrient pool, in addition to the brine pool, is essential to successfully model and reproduce field observations. The presence of a biofilm attached to the ice walls could act as a water-retaining substrate forming microenvironments with chemical gradients within the brine channels. The effect of biofilm on nitrogen dynamics (concentration and isotopic composition) in sea ice will be discussed as well as potential implications for other parameters (phosphate, carbon, oxygen). This calls for the integration of the biofilm concept into the current view of sea-ice biogeochemistry
We show that young, snow-covered ice has a potential for sea-ice-to-air CO 2 release during winte... more We show that young, snow-covered ice has a potential for sea-ice-to-air CO 2 release during winter and spring in the Arctic Ocean north of Svalbard. Young thin sea ice was characterized by high salinities and thus porosity, while the surface of thicker sea ice was relatively warm (>-7.5°C), due to a thick insulating snow cover, even though air temperatures were as low as-40°C. During these conditions, brine volume fractions of sea ice were high, providing potentially favorable conditions for gas exchange between sea ice and overlying air even in midwinter. Although the potential CO 2 flux through the sea ice decreased due to the presence of the snow, the snow surface still is a CO 2 source to the atmosphere for low snow density and thin snow conditions. Especially young ice formed in leads, without snow cover, is important for the CO 2 flux from the ice pack as the fluxes are an order of magnitude higher than for snow-covered older ice.
The influence of seawater CO 2 concentration on the size distribution of suspended particles (2-6... more The influence of seawater CO 2 concentration on the size distribution of suspended particles (2-60 µm) and on phytoplankton abundance was investigated during a mesocosm experiment at the large scale facility (LFS) in Bergen, Norway, in the frame of the Pelagic Ecosystem CO 2 Enrichment study (PeECE II). In nine outdoor enclosures the BGD 4, 4101-4133, 2007 CO 2 effects on particle size and phytoplankton abundance A. Engel et al.
We present an Arctic seasonal survey of carbon dioxide partial pressure (pCO 2) dynamics within s... more We present an Arctic seasonal survey of carbon dioxide partial pressure (pCO 2) dynamics within sea ice brine and related air-ice CO 2 fluxes. The survey was carried out from early spring to the beginning of summer in the Arctic coastal waters of the Amundsen Gulf. High concentrations of pCO 2 (up to 1834 matm) were observed in the sea ice in early April as a consequence of concentration of solutes in brines, CaCO 3 precipitation and microbial respiration. CaCO 3 precipitation was detected through anomalies in total alkalinity (TA) and dissolved inorganic carbon (DIC). This precipitation seems to have occurred in highly saline brine in the upper part of the ice cover and in bulk ice. As summer draws near, the ice temperature increases and brine pCO 2 shifts from a large supersaturation (1834 matm) to a marked undersaturation (down to almost 0 matm). This decrease was ascribed to brine dilution by ice meltwater, dissolution of CaCO 3 and photosynthesis during the sympagic algal bloom. The magnitude of the CO 2 fluxes was controlled by ice temperature (through its control on brine volume and brine channels connectivity) and the concentration gradient between brine and the atmosphere. However, the state of the ice-interface clearly affects air-ice CO 2 fluxes.
HAL (Le Centre pour la Communication Scientifique Directe), Nov 12, 2007
The influence of seawater CO 2 concentration on the size distribution of suspended particles (2-6... more The influence of seawater CO 2 concentration on the size distribution of suspended particles (2-60 µm) and on phytoplankton abundance was investigated during a mesocosm experiment at the large scale facility (LFS) in Bergen, Norway, in the frame of the Pelagic Ecosystem CO 2 Enrichment study (PeECE II). In nine outdoor enclosures the BGD 4, 4101-4133, 2007 CO 2 effects on particle size and phytoplankton abundance A. Engel et al.
The PIPERS cruise on N. B. Palmer into the early winter Ross Sea took place between April and Jun... more The PIPERS cruise on N. B. Palmer into the early winter Ross Sea took place between April and June 2017. PIPERS was a unique opportunity to investigate biogeochemistry of pack ice during early stages of ice formation. We will present insights of the dynamics of sympagic microalgae assemblages, nutrients, particulate organic carbon and 2 potent greenhouse gases (carbon dioxide and nitrous oxide) during early ice growth. The comparison of CO2 fluxes over consolidated and unconsolidated ice show that 1) sea ice acts as a source of CO2 for the atmosphere 2) largest fluxes occur at the earliest sea ice growth stages (i.e. frazil ice, unconsolidated grey ice, pancake ice). Large fluxes are due to ongoing active rejection of impurities, high porosity of highly saline/high temperature young ice, and the absence of snow. Overall, snow appears to restrict CO2 fluxes. In some cases, fluxes over snow appears to be nil or even opposite to fluxes over bare ice. Therefore, while snow is often view as a transient buffer for air-ice gases fluxes, the role of snow appears to be more complicated. The new measurements of CO2 fluxes over young ice carried out during PIPERS potentially allow to complete a budget of CO2 fluxes over Antarctic pack ice by filling a significant gap
With an extent varying between a maximum of 19 × 106 km2 in late winter and a minimum of 3 × 106 ... more With an extent varying between a maximum of 19 × 106 km2 in late winter and a minimum of 3 × 106 km2 in late summer, Antarctic sea ice is one of the largest ecosystems on Earth, most of which consists of annual pack ice. Primary production in-situ measurements in Antarctic sea ice, using either oxygen-based or tracer incubation methods, are relatively tricky to achieve and remain scarce. Thus, to estimate large-scale Antarctic sea-ice primary productivity, two approaches have been used. First, the use of sea-ice biogeochemical models suggest that Antarctic pack ice contributes to a small but significant fraction (10–28%) of the primary production in the ice-covered area of the Southern Ocean. Second, accumulation of organic matter trapped within sea ice during the growth season is likely to be representative of the net community production. More than 20 years ago, Legendre et al. (1992) used the few available observations to infer Antarctic sea-ice primary productivity. We believe that it is time to revisit this estimation by accounting from a much larger compilation of data (historical to present). Here, we present the first results using an updated dataset of historical ice cores sampled between 1989 and 2017 (± 400 pack-ice cores). These allow us to provide an updated estimation of the sea-ice primary production based on in-situ data, and its contribution to the SIZ and Southern Ocean. A comparison between pack and fast ice (± 110 fast- ice cores) will be also briefly discussed
These two observatories help to establish a network of observatories across the Arctic, which is ... more These two observatories help to establish a network of observatories across the Arctic, which is funded through the NSF Arctic Observatory Network (AON) program. The other flux stations that participate in this network are located near Abisko, Sweden and Zackenberg, Greenland, as well as a series of sites across Arctic Canada. The goal of making flux measurements made at these sites is to: 1) quantify and understand the controls of carbon, water, and energy exchange at each site, 2) permit cross-site synthesis of the carbon, water, and energy fluxes across the representative terrestrial ecosystems in the Arctic, and 3) parameterize and validate ecosystem and land-surface FluxLetter The Newsletter of FLUXNET
Antarctic sea ice is a seasonal source of iron (Fe) to the Southern Ocean (SO), where surface wat... more Antarctic sea ice is a seasonal source of iron (Fe) to the Southern Ocean (SO), where surface waters Fe levels are otherwise generally low. The effectiveness of Fe released from melting sea ice does not only depends on the magnitude of the supply, but also on the biological Fe demand. Here, we hypothesize that Fe uptake rates by sea-ice algae and under-ice phytoplankton are higher than the rates reported for open ocean phytoplankton in the SO. We performed 55Fe and carbon (14C) short-term uptake field measurements in, on and under Antarctic sea ice. Our results show that over 90% of Fe taken up by sea-ice algae and under-ice phytoplankton was found on the outside of the algal cells. The intracellular Fe (Feintra) uptake rates were high and reached up 68, 194 and 203 pmol Fe L− 1 d− 1 in seawater, bottom ice and over-ice respectively. Overall C uptake in bottom sea ice was low, ranging between 0.03 and 3.2 µmol C L− 1 d− 1, but similar to previous sea-ice studies. The Feintra:C ratio...
While representing less than 5% of the total ice cover around Antarctica, landfast sea ice is nev... more While representing less than 5% of the total ice cover around Antarctica, landfast sea ice is nevertheless an important habitat known to exhibit high biomass levels at the ocean/ice interface, with particulate organic carbon (POC) concentrations easily reaching 2000 μmol C L–1 during spring bloom. Surprisingly, together with the POC increase in bottom ice, fieldwork measurements performed in East Antarctica (Adélie Land 2011, McMurdo Sound 2012, Prydz Bay 2015) of nitrate and phosphate concentrations report a simultaneous increase with concentrations exceeding those of underlying seawater, suggesting an intense remineralization and nitrification processes within the ice. This goes against the classic view of nutrients being consumed during the growth season and regenerated after the height of the bloom. Regardless of the high nitrate levels available in the ice, increasing total nitrogen concentrations also suggest still more nitrogen from the underlying seawater was brought into the ice. Results of a NPZD-model indicates that a second nutrient pool, in addition to the brine pool, is essential to successfully model and reproduce field observations. The presence of a biofilm attached to the ice walls could act as a water-retaining substrate forming microenvironments with chemical gradients within the brine channels. The effect of biofilm on nitrogen dynamics (concentration and isotopic composition) in sea ice will be discussed as well as potential implications for other parameters (phosphate, carbon, oxygen). This calls for the integration of the biofilm concept into the current view of sea-ice biogeochemistry
We show that young, snow-covered ice has a potential for sea-ice-to-air CO 2 release during winte... more We show that young, snow-covered ice has a potential for sea-ice-to-air CO 2 release during winter and spring in the Arctic Ocean north of Svalbard. Young thin sea ice was characterized by high salinities and thus porosity, while the surface of thicker sea ice was relatively warm (>-7.5°C), due to a thick insulating snow cover, even though air temperatures were as low as-40°C. During these conditions, brine volume fractions of sea ice were high, providing potentially favorable conditions for gas exchange between sea ice and overlying air even in midwinter. Although the potential CO 2 flux through the sea ice decreased due to the presence of the snow, the snow surface still is a CO 2 source to the atmosphere for low snow density and thin snow conditions. Especially young ice formed in leads, without snow cover, is important for the CO 2 flux from the ice pack as the fluxes are an order of magnitude higher than for snow-covered older ice.
The influence of seawater CO 2 concentration on the size distribution of suspended particles (2-6... more The influence of seawater CO 2 concentration on the size distribution of suspended particles (2-60 µm) and on phytoplankton abundance was investigated during a mesocosm experiment at the large scale facility (LFS) in Bergen, Norway, in the frame of the Pelagic Ecosystem CO 2 Enrichment study (PeECE II). In nine outdoor enclosures the BGD 4, 4101-4133, 2007 CO 2 effects on particle size and phytoplankton abundance A. Engel et al.
We present an Arctic seasonal survey of carbon dioxide partial pressure (pCO 2) dynamics within s... more We present an Arctic seasonal survey of carbon dioxide partial pressure (pCO 2) dynamics within sea ice brine and related air-ice CO 2 fluxes. The survey was carried out from early spring to the beginning of summer in the Arctic coastal waters of the Amundsen Gulf. High concentrations of pCO 2 (up to 1834 matm) were observed in the sea ice in early April as a consequence of concentration of solutes in brines, CaCO 3 precipitation and microbial respiration. CaCO 3 precipitation was detected through anomalies in total alkalinity (TA) and dissolved inorganic carbon (DIC). This precipitation seems to have occurred in highly saline brine in the upper part of the ice cover and in bulk ice. As summer draws near, the ice temperature increases and brine pCO 2 shifts from a large supersaturation (1834 matm) to a marked undersaturation (down to almost 0 matm). This decrease was ascribed to brine dilution by ice meltwater, dissolution of CaCO 3 and photosynthesis during the sympagic algal bloom. The magnitude of the CO 2 fluxes was controlled by ice temperature (through its control on brine volume and brine channels connectivity) and the concentration gradient between brine and the atmosphere. However, the state of the ice-interface clearly affects air-ice CO 2 fluxes.
HAL (Le Centre pour la Communication Scientifique Directe), Nov 12, 2007
The influence of seawater CO 2 concentration on the size distribution of suspended particles (2-6... more The influence of seawater CO 2 concentration on the size distribution of suspended particles (2-60 µm) and on phytoplankton abundance was investigated during a mesocosm experiment at the large scale facility (LFS) in Bergen, Norway, in the frame of the Pelagic Ecosystem CO 2 Enrichment study (PeECE II). In nine outdoor enclosures the BGD 4, 4101-4133, 2007 CO 2 effects on particle size and phytoplankton abundance A. Engel et al.
The PIPERS cruise on N. B. Palmer into the early winter Ross Sea took place between April and Jun... more The PIPERS cruise on N. B. Palmer into the early winter Ross Sea took place between April and June 2017. PIPERS was a unique opportunity to investigate biogeochemistry of pack ice during early stages of ice formation. We will present insights of the dynamics of sympagic microalgae assemblages, nutrients, particulate organic carbon and 2 potent greenhouse gases (carbon dioxide and nitrous oxide) during early ice growth. The comparison of CO2 fluxes over consolidated and unconsolidated ice show that 1) sea ice acts as a source of CO2 for the atmosphere 2) largest fluxes occur at the earliest sea ice growth stages (i.e. frazil ice, unconsolidated grey ice, pancake ice). Large fluxes are due to ongoing active rejection of impurities, high porosity of highly saline/high temperature young ice, and the absence of snow. Overall, snow appears to restrict CO2 fluxes. In some cases, fluxes over snow appears to be nil or even opposite to fluxes over bare ice. Therefore, while snow is often view as a transient buffer for air-ice gases fluxes, the role of snow appears to be more complicated. The new measurements of CO2 fluxes over young ice carried out during PIPERS potentially allow to complete a budget of CO2 fluxes over Antarctic pack ice by filling a significant gap
With an extent varying between a maximum of 19 × 106 km2 in late winter and a minimum of 3 × 106 ... more With an extent varying between a maximum of 19 × 106 km2 in late winter and a minimum of 3 × 106 km2 in late summer, Antarctic sea ice is one of the largest ecosystems on Earth, most of which consists of annual pack ice. Primary production in-situ measurements in Antarctic sea ice, using either oxygen-based or tracer incubation methods, are relatively tricky to achieve and remain scarce. Thus, to estimate large-scale Antarctic sea-ice primary productivity, two approaches have been used. First, the use of sea-ice biogeochemical models suggest that Antarctic pack ice contributes to a small but significant fraction (10–28%) of the primary production in the ice-covered area of the Southern Ocean. Second, accumulation of organic matter trapped within sea ice during the growth season is likely to be representative of the net community production. More than 20 years ago, Legendre et al. (1992) used the few available observations to infer Antarctic sea-ice primary productivity. We believe that it is time to revisit this estimation by accounting from a much larger compilation of data (historical to present). Here, we present the first results using an updated dataset of historical ice cores sampled between 1989 and 2017 (± 400 pack-ice cores). These allow us to provide an updated estimation of the sea-ice primary production based on in-situ data, and its contribution to the SIZ and Southern Ocean. A comparison between pack and fast ice (± 110 fast- ice cores) will be also briefly discussed
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