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  • 1
    Article
    Article
    Phosphorus cycling in the North and South Atlantic Ocean subtropical gyres (2008)
    Associated volumes
    Details Availability
    In: Nature geoscience, London : Nature Publishing Group, 2008, 1(2008), Seite 439-443, 1752-0894
    In: volume:1
    In: year:2008
    In: pages:439-443
    Description / Table of Contents: Despite similar physical properties, the Northern and Southern Atlantic subtropical gyres have different biogeochemical regimes. The Northern subtropical gyre, which is subject to iron deposition from Saharan dust 1, is depleted in the nutrient phosphate, possibly as a result of iron-enhanced nitrogen fixation 2. Although phosphate depleted, rates of carbon fixation in the euphotic zone of the North Atlantic subtropical gyre are comparable to those of the South Atlantic subtropical gyre 3, which is not phosphate limited. Here we use the activity of the phosphorus-specific enzyme alkaline phosphatase to show potentially enhanced utilization of dissolved organic phosphorus occurring over much of the North Atlantic subtropical gyre. We find that during the boreal spring up to 30% of primary production in the North Atlantic gyre is supported by dissolved organic phosphorus. Our diagnostics and composite map of the surface distribution of dissolved organic phosphorus in the subtropical Atlantic Ocean reveal shorter residence times in the North Atlantic gyre than the South Atlantic gyre. We interpret the asymmetry of dissolved organic phosphorus cycling in the two gyres as a consequence of enhanced nitrogen fixation in the North Atlantic Ocean 4, which forces the system towards phosphorus limitation. We suggest that dissolved organic phosphorus utilization may contribute to primary production in other phosphorus-limited ocean settings as well.
    Type of Medium: Article
    Pages: graph. Darst
    ISSN: 1752-0894
    Language: English
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  • 2
    Online Resource
    Online Resource
    Advektive Pfade von Nährstoffen und ökologischen Schlüsselsubstanzen in der Arktis : Schlussbericht (2022)
    Bremerhaven : [Alfred-Wegener-Institute Helmholtz-Center for Polar and Marine Research]
    Details Availability
    Keywords: Forschungsbericht ; Nordpolarmeer ; Zirkulation ; Mengenelement ; Nährstoffeintrag
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (21 Seiten, 11,53 MB) , Diagramme, Karten
    URL: https://edocs.tib.eu/files/e01fb23/1860722377.pdf
    URL: https://doi.org/10.2314/KXP:1860722377
    DOI: 10.2314/KXP:1860722377
    Language: German
    Note: Förderkennzeichen BMBF 03F0807A [richtig] - 03V01461 [falsch] , Laufzeit: 01.07.2018 bis 31.12.2021 , Unterschiede zwischen dem gedruckten Dokument und der elektronischen Ressource können nicht ausgeschlossen werden
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  • 3
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    Properties of the Atlantic derived halocline waters over the Laptev Sea continental margin: Evidence from 2002 to 2009 (2011)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 116 (C10). C10024.
    Details
    Publication Date: 2019-09-23
    Description: A series of transects carried out in 2002–2009 across the Laptev Sea continental margin show consistent cross‐slope differences of the lower halocline water (LHW). Over the slope the LHW core is on average warmer and saltier by 0.39°C and 0.26 practical salinity unit, respectively, relative to the off‐slope LHW. Underlying Atlantic water (AW) thermohaline properties exhibit an opposite pattern; it is colder and fresher over the slope and warmer and saltier off the slope. Although on‐slope and off‐slope LHWs have different formation histories, our results suggest that an important part of the heat and salt lost from the AW is gained by the overlying LHW over the continental slope area. This implies the role of enhanced vertical mixing over the sloping topography, which contributes to the difference between the on‐ and off‐slope LHW properties. The distribution of chemical tracers (dissolved oxygen and nutrients) provides further evidence supporting this interpretation and additionally suggests that the LHW may also be influenced by water from the outer shelf.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2011JC007269
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Addressing Arctic Challenges Requires a Synoptic Ocean Survey (2019)
    AGU (American Geophysical Union)
    In:  Eos: Earth & Space Science News, 100 .
    Details
    Publication Date: 2020-02-05
    Description: A coordinated effort involving trailblazing science — and icebreaking ships — from many nations is needed to fill gaps in our understanding of the Arctic Ocean and how it’s changing.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2019EO136200
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  • 5
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    Advection of Sea-ice meltwater and Halocline Water Along the Siberian Continental Margin (2014)
    In:  [Poster] In: AGU Fall Meeting 2014, 15.12.-19.12.2014, San Francisco, California, USA .
    Details
    Publication Date: 2015-02-23
    Description: OS51C-1006 Our study is based on hydrochemical and stable oxygen isotope data at the Laptev Sea continental slope from summers 2005-2009 and reveals a general pattern in water mass distribution and potential shelf-basin exchange. Despite considerable inter-annual variations, a frontal system can be inferred between shelf, continental slope and central Eurasian Basin waters in the upper 100 m of the water column along the continental slope. Net sea-ice melt is consistently found at the continental slope. However, the sea-ice meltwater signal is independent from the local retreat of the sea-ice edge and appears to be advected from upwind locations. In addition to the along-slope frontal system at the continental shelf break, a strong gradient is identified on the Laptev Sea shelf at ~122-126°E with an eastward increase of riverine and sea-ice related brine water contents. These waters cross the shelf break at ~140°E and feed the Low Salinity Halocline Water (LSHW, salinity S〈33) in the upper 50 m of the water column. High silicate concentrations in Laptev Sea bottom waters may lead to speculation about a link to the local silicate maximum found within the salinity range of ~33 to 34.5, typical for the Lower Halocline Water (LHW) at the continental slope. However brine signatures and nutrient ratios from the central Laptev Sea differ from those observed at the continental slope. Similar to the advection of the sea-ice melt signal along the Laptev Sea continental slope the nutrient signal at 50-70 m water depth within the LHW might also be fed by advection parallel to the slope. Thus, our analyses suggest that advective processes from upstream locations play a significant role in the meltwater distribution and halocline formation in the northern Laptev Sea. Inter-annual variations within the properties of LHW are further investigated.
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 6
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    Origin of freshwater and polynya water in the Arctic Ocean halocline in summer 2007 (2011)
    Elsevier
    In:  Progress in Oceanography, 91 . pp. 482-495.
    Details
    Publication Date: 2019-09-23
    Description: Extremely low summer sea-ice coverage in the Arctic Ocean in 2007 allowed extensive sampling and a wide quasi-synoptic hydrographic and δ18O dataset could be collected in the Eurasian Basin and the Makarov Basin up to the Alpha Ridge and the East Siberian continental margin. With the aim of determining the origin of freshwater in the halocline, fractions of river water and sea-ice meltwater in the upper 150 m were quantified by a combination of salinity and δ18O in the Eurasian Basin. Two methods, applying the preformed phosphate concentration (PO*) and the nitrate-to-phosphate ratio (N/P), were compared to further differentiate the marine fraction into Atlantic and Pacific-derived contributions. While PO*-based assessments systematically underestimate the contribution of Pacific-derived waters, N/P-based calculations overestimate Pacific-derived waters within the Transpolar Drift due to denitrification in bottom sediments at the Laptev Sea continental margin. Within the Eurasian Basin a west to east oriented front between net melting and production of sea-ice is observed. Outside the Atlantic regime dominated by net sea-ice melting, a pronounced layer influenced by brines released during sea-ice formation is present at about 30 to 50 m water depth with a maximum over the Lomonosov Ridge. The geographically distinct definition of this maximum demonstrates the rapid release and transport of signals from the shelf regions in discrete pulses within the Transpolar Drift. The ratio of sea-ice derived brine influence and river water is roughly constant within each layer of the Arctic Ocean halocline. The correlation between brine influence and river water reveals two clusters that can be assigned to the two main mechanisms of sea-ice formation within the Arctic Ocean. Over the open ocean or in polynyas at the continental slope where relatively small amounts of river water are found, sea-ice formation results in a linear correlation between brine influence and river water at salinities of about 32 to 34. In coastal polynyas in the shallow regions of the Laptev Sea and southern Kara Sea, sea-ice formation transports river water into the shelf’s bottom layer due to the close proximity to the river mouths. This process therefore results in waters that form a second linear correlation between brine influence and river water at salinities of about 30 to 32. Our study indicates which layers of the Arctic Ocean halocline are primarily influenced by sea-ice formation in coastal polynyas and which layers are primarily influenced by sea-ice formation over the open ocean. Accordingly we use the ratio of sea-ice derived brine influence and river water to link the maximum in brine influence within the Transpolar Drift with a pulse of shelf waters from the Laptev Sea that was likely released in summer 2005.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1016/j.pocean.2011.07.017
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Sources and sinks of N2O in the subpolar and polar North Atlantic (2020)
    In:  [Talk] In: Ocean Sciences Meeting 2020, 16.-21.02.2020, San Diego, USA .
    Details
    Publication Date: 2020-03-04
    Description: The Arctic Ocean is particularly sensitive to climate change. Its ecosystem structure and function are prone to be disturbed by fast warming and massive retreat of sea-ice, which in turn, might result in feedbacks on climate. Moreover, such drastic changes are expected to influence the meridional fluxes of heat, freshwater and biogeochemical tracers between subpolar areas and the Arctic. As the third most important greenhouse gas and major ozone-depleting substance in the stratosphere, nitrous oxide (N2O) is a crucial gas to study in order to assess the ocean’s role in the production and exchange of climate-relevant compounds to the atmosphere. Between 2018 and 2019 we conducted ship-based surveys to elucidate the source-sink dynamics of N2O in the subpolar-polar North Atlantic. Based on results from those campaigns, we show the distribution and spatial variability of surface N2O, which ranged from moderate supersaturation (positive sea-air fluxes) in ice-free subpolar areas to unusually strong undersaturation (negative sea-air fluxes) in partially or fully ice-covered areas. We also present a comprehensive overview of the water column distribution of N2O in the region, and by combining this data with hydrographic and chemical (O2 and inorganic nutrients) information, we trace back the origin of the dominant water masses so as to illustrate the connectivity between the Fram Strait and the Nordic Seas off southeast Greenland. This analysis is used to discuss how the meridional water mass exchange in the region influences the balance of local vs. remote N2O production and its spatial variability. Furthermore, we use the results from collocated molecular analyses (functional gene markers) to infer the occurrence and abundances of the main microbial communities responsible for the cycling of N2O. This contribution is relevant for assessments of expected changes in trace gas emissions with further climate-driven changes in the Arctic Ocean.
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 8
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    Freshwater and polynya components of the shelf-derived Arctic Ocean halocline in summer 2007 identified by stable oxygen isotopes (2011)
    In:  [Poster] In: AGU Fall Meeting 2011, 05.12.-09.12.2011, San Francisco, California, USA .
    Details
    Publication Date: 2019-09-23
    Description: With the aim of determining the origin of freshwater in the halocline, fractions of river water and sea-ice meltwater (or brine influence from sea-ice formation) in the upper 150 m were quantified by a combination of salinity and _18O and nutrients in the Eurasian basins and the Makarov Basin. Our study indicates which layers of the Arctic Ocean halocline are primarily influenced by sea-ice formation in coastal polynyas and which are primarily influenced by sea-ice formation over the open ocean. With the ongoing changes in sea-ice coverage in the Arctic Ocean it can be expected that these processes will change in the immediate future and that the relative contributions to the halocline will change accordingly. Within the Eurasian Basin a west to east oriented front between net melting and production of sea-ice is observed. Outside the Atlantic regime dominated by net sea-ice melting, a pronounced layer influenced by brines released during sea-ice formation is present at about 30 to 50 m water depth with a maximum over the Lomonosov Ridge. The geographically distinct definition of this maximum demonstrates the rapid release and transport of signals from the shelf regions in discrete pulses within the Transpolar Drift. We use the ratio of sea-ice derived brine influence and river water to link the maximum in brine influence within the Transpolar Drift with a pulse of shelf waters from the Laptev Sea likely released in summer 2005. For a distinction of Atlantic and Pacific-derived contributions the initial phosphate corrected for mineralization with oxygen (PO*) and alternatively the nitrate to phosphate ratio (N/P) in each sample were used. While PO*-based assessments systematically underestimate the contribution of Pacific-derived waters, N/P-based calculations overestimate Pacific-derived waters within the Transpolar Drift due to denitrification in bottom sediments of the Laptev Sea. The extent of Pacific-derived water in the Arctic Ocean was approximately limited by the position of the Lomonosov Ridge in 2007. The ratio of sea-ice derived brine influence and river water is roughly constant within each layer of the Arctic Ocean halocline. The correlation between brine influence and river water reveals two clusters that can be assigned to the two main mechanisms of sea-ice formation within the Arctic Ocean. Over the open ocean or in polynyas at the continental slope sea-ice formation results in a linear correlation between brine influence and river water at salinities of ~ 32 to 34. In coastal polynyas in the shallow regions of the Laptev Sea and southern Kara Sea, sea-ice formation transports river water into the shelf’s bottom layer due to the close proximity to the river mouths. This process results in a second linear correlation between brine influence and river water at salinities of ~ 30 to 32.
    Type: Conference or Workshop Item , NonPeerReviewed
    Format: text
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    OceanRep: Poster
  • 9
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    Summertime Amino Acid and Carbohydrate Patterns in Particulate and Dissolved Organic Carbon Across Fram Strait (2021)
    Frontiers
    Details
    Publication Date: 2024-02-07
    Description: Amino acids (AA) and carbohydrates (CHO) are important components of the marine organic carbon cycle. Produced mainly by phytoplankton as part of the particulate organic carbon (POC) fraction, these compounds can be released into the outer medium where they become part of the dissolved organic carbon (DOC) pool and are rapidly taken up by heterotrophs (e.g., bacteria). We investigated the quantity and quality of POC and DOC, AA and CHO composition in both pools in three different water masses in the Fram Strait (Arctic Ocean) in summer 2017. Polar Waters and Atlantic Waters showed similar concentrations of particulate and dissolved AA and CHO, despite Polar Waters showing the highest DOC concentrations. In Mixed Waters, where the two water masses mix with each other and with melting sea ice, the concentrations of particulate and dissolved AA and CHO were highest. AA and CHO composition differed substantially between the particulate and dissolved fractions. The particulate fraction (〉0.7 μm) was enriched in essential AA and the CHO galactose, xylose/mannose, and muramic acid. In the dissolved fraction non-essential AA, several neutral CHO, and acidic and amino CHO were enriched. We further investigated different size fractions of the particulate matter using a separate size fractionation approach (0.2–0.7 μm, 0.7–10 μm and 〉10 μm). The chemical composition of the 0.2–0.7 μm size-fraction had a higher contribution of non-essential AA and acidic and amino sugars, setting them apart from the 0.7–10 μm and 〉10 μm fractions, which showed the same composition. We suggest that the relative differences observed between different size fractions and DOC with regards to AA and CHO composition can be used to evaluate the state of organic matter processing and evaluate the contribution of autotrophic phytoplankton or more heterotrophic biomass. In the future, changing conditions in the Central Arctic Ocean (Atlantification, warming, decreasing ice concentrations) may increase primary production and consequently degradation. The AA and CHO signatures left behind after production and/or degradation processes occurred, could be used as tracers after the fact to infer changes in microbial loop processes and food web interactions.
    Type: Article , PeerReviewed
    Format: text
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  • 10
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    Physical oceanography measurements during POLARSTERN cruise PS99.2 measured from a Zodiac (2018)
    PANGAEA
    Details
    Publication Date: 2023-03-17
    Keywords: ARK-XXX/1.2; Autonomous underwater vehicle; AUV; AUV ID 038; AWI_PhyOce; CTD, Sea-Bird, SBE 19plus; DATE/TIME; DEPTH, water; Fluorescence; FRAM; FRontiers in Arctic marine Monitoring; Hausgarten; LATITUDE; LONGITUDE; Long-term Investigation at AWI-Hausgarten off Svalbard; MATLAB date; North Greenland Sea; Physical Oceanography @ AWI; Polarstern; Pressure, water; PS99/075-1; PS99.2; Salinity; Temperature, water
    Type: Dataset
    Format: text/tab-separated-values, 3500 data points
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    DATA PANGAEA
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