| 1. |
- Yager, P. L., et al.
(författare)
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ASPIRE The Amundsen Sea Polynya International Research Expedition
- 2012
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Ingår i: Oceanography. - : The Oceanography Society. - 1042-8275. ; 25:3, s. 40-53
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Tidskriftsartikel (refereegranskat)abstract
- In search of an explanation for some of the greenest waters ever seen in coastal Antarctica and their possible link to some of the fastest melting glaciers and declining summer sea ice, the Amundsen Sea Polynya International Research Expedition (ASPIRE) challenged the capabilities of the US Antarctic Program and RVIB Nathaniel B. Palmer during Austral summer 2010-2011. We were well rewarded by both an extraordinary research platform and a truly remarkable oceanic setting. Here we provide further insights into the key questions that motivated our sampling approach during ASPIRE and present some preliminary findings, while highlighting the value of the Palmer for accomplishing complex, multifaceted oceanographic research in such a challenging environment.
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| 2. |
- Rabe, Benjamin, et al.
(författare)
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The MOSAiC Distributed Network: Observing the coupled Arctic system with multidisciplinary, coordinated platforms
- 2024
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Ingår i: Elementa. - 2325-1026. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Central Arctic properties and processes are important to the regional and global coupled climate system. The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) Distributed Network (DN) of autonomous ice-tethered systems aimed to bridge gaps in our understanding of temporal and spatial scales, in particular with respect to the resolution of Earth system models. By characterizing variability around local measurements made at a Central Observatory, the DN covers both the coupled system interactions involving the ocean-ice-atmosphere interfaces as well as three-dimensional processes in the ocean, sea ice, and atmosphere. The more than 200 autonomous instruments (“buoys”) were of varying complexity and set up at different sites mostly within 50 km of the Central Observatory. During an exemplary midwinter month, the DN observations captured the spatial variability of atmospheric processes on sub-monthly time scales, but less so for monthly means. They show significant variability in snow depth and ice thickness, and provide a temporally and spatially resolved characterization of ice motion and deformation, showing coherency at the DN scale but less at smaller spatial scales. Ocean data show the background gradient across the DN as well as spatially dependent time variability due to local mixed layer sub-mesoscale and mesoscale processes, influenced by a variable ice cover. The second case (May–June 2020) illustrates the utility of the DN during the absence of manually obtained data by providing continuity of physical and biological observations during this key transitional period. We show examples of synergies between the extensive MOSAiC remote sensing observations and numerical modeling, such as estimating the skill of ice drift forecasts and evaluating coupled system modeling. The MOSAiC DN has been proven to enable analysis of local to mesoscale processes in the coupled atmosphere-ice-ocean system and has the potential to improve model parameterizations of important, unresolved processes in the future.
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| 3. |
- Swalethorp, Rasmus, et al.
(författare)
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Microzooplankton distribution in the Amundsen Sea Polynya (Antarctica) during an extensive Phaeocystis antarctica bloom
- 2019
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Ingår i: Progress in Oceanography. - : Elsevier. - 0079-6611 .- 1873-4472. ; 170, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- In Antarctica, summer is a time of extreme environmental shifts resulting in large coastal phytoplankton blooms fueling the food web. Despite the importance of the microbial loop in remineralizing biomass from primary production, studies of how microzooplankton communities respond to such blooms in the Southern Ocean are rather scarce. Microzooplankton (ciliate and dinoflagellate) communities were investigated combining microscopy and 18S rRNA sequencing analyses in the Amundsen Sea Polynya during an extensive summer bloom of Phaeocystis antarctica. The succession of microzooplankton was further assessed during a 15-day induced bloom microcosm experiment. Dinoflagellates accounted for up to 59 % of the microzooplankton biomass in situ with Gymnodinium spp., Protoperidiwn spp. and Gyrodinium spp. constituting 89 % of the dinoflagellate biomass. Strobilidium spp., Strombidium spp. and tintinids represented 90 % of the ciliate biomass. Gymnodiniwn, Gyrodinium and tintinnids are known grazers of Phaeocystis, suggesting that this prymnesiophyte selected for the key microzooplankton taxa. Availability of other potential prey, such as diatoms, heterotrophic nanoflagellates and bacteria, also correlated to changes in microzooplankton community structure. Overall, both heterotrophy and mixotrophy appeared to be key trophic strategies of the dominant microzooplankton observed, suggesting that they influence carbon flow in the microbial food web through top-down control on the phytoplankton community.
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| 4. |
- Titelman, Josefin, 1973, et al.
(författare)
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Copepod feeding stimulates bacterioplankton in a low phosphorus system
- 2008
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Ingår i: Aquatic Biology. - : Inter-Research Science Center. - 1864-7782 .- 1864-7790. ; 2:2, s. 131-141
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT: Zooplankton sloppy feeding releases high-quality dissolved organic matter, which is readily used by microbes. We hypothesized that in phosphorus (P) limited environments, released dissolved DNA may be a particularly important source of P for bacteria. In an incubation experiment with water from the Bothnian Bay, Sweden, we investigated the short-term effect of copepod feeding activity on bacterial production, DNA uptake and phosphatase activity. Consistent patterns in bacterial activity measures suggested that copepod feeding activity stimulated phosphatase activity, DNA uptake and production. The P taken up as dissolved DNA exceeded cellular P requirements. We speculate that bacterioplankton cells in the Bothnian Bay store excess P intracellularly during times of extensive sloppy feeding, which may then subsequently be utilized to prevent P limitation of growth.
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| 5. |
- Yager, P. L., et al.
(författare)
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A carbon budget for the Amundsen Sea Polynya, Antarctica: Estimating net community production and export in a highly productive polar ecosystem
- 2016
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Ingår i: Elementa-Science of the Anthropocene. - : University of California Press. - 2325-1026. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- Polynyas, or recurring areas of seasonally open water surrounded by sea ice, are foci for energy and material transfer between the atmosphere and the polar ocean. They are also climate sensitive, with both sea ice extent and glacial melt influencing their productivity. The Amundsen Sea Polynya (ASP) is the greenest polynya in the Southern Ocean, with summertime chlorophyll a concentrations exceeding 20 mu g L-1. During the Amundsen Sea Polynya International Research Expedition (ASPIRE) in austral summer 2010-11, we aimed to determine the fate of this high algal productivity. We collected water column profiles for total dissolved inorganic carbon (DIC) and nutrients, particulate and dissolved organic matter, chlorophyll a, mesozoo-plankton, and microbial biomass to make a carbon budget for this ecosystem. We also measured primary and secondary production, community respiration rates, vertical particle flux and fecal pellet production and grazing. With observations arranged along a gradient of increasing integrated dissolved inorganic nitrogen drawdown (Delta DIN; 0.027-0.74 mol N m(-2)), changes in DIC in the upper water column (ranging from 0.2 to 4.7 mol C m(-2)) and gas exchange (0-1.7 mol C m(-2)) were combined to estimate early season net community production (sNCP; 0.2-5.9 mol C m(-2)) and then compared to organic matter inventories to estimate export. From a phytoplankton bloom dominated by Phaeocystis antarctica, a high fraction (up to similar to 60%) of sNCP was exported to sub-euphotic depths. Microbial respiration remineralized much of this export in the mid waters. Comparisons to short-term (2-3 days) drifting traps and a year-long moored sediment trap capturing the downward flux confirmed that a relatively high fraction (3-6%) of the export from similar to 100 m made it through the mid waters to depth. We discuss the climate-sensitive nature of these carbon fluxes, in light of the changing sea ice cover and melting ice sheets in the region.
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