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  • Copernicus Publications (EGU)  (3)
  • American Meteorological Society  (1)
  • Berlin : Duncker & Humblot  (1)
  • 1
    Online Resource
    Online Resource
    Berlin : Duncker & Humblot
    Keywords: Electronic books
    Type of Medium: Online Resource
    Pages: 1 online resource (103 pages)
    Edition: 1st ed.
    ISBN: 9783428427581
    Series Statement: Schriften des Rheinisch-Westfälischen Instituts für Wirtschaftsforschung
    Language: German
    Note: Description based on publisher supplied metadata and other sources
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  • 2
    Publication Date: 2021-03-19
    Description: A long-term mean flow field for the subpolar North Atlantic region with a horizontal resolution of approximately 25km is created by gridding Argo-derived velocity vectors using two different topography-following interpolation schemes. The 10-day float displacements in the typical drift depths of 1000 to 1500m represent the flow in the Labrador Sea Water density range. Both mapping algorithms separate the flow field into potential vorticity (PV) conserving, i.e., topography-following contribution and a deviating part, which we define as the eddy contribution. To verify the significance of the separation, we compare the mean flow and the eddy kinetic energy (EKE), derived from both mapping algorithms, with those obtained from multiyear mooring observations. The PV-conserving mean flow is characterized by stable boundary currents along all major topographic features including shelf breaks and basin-interior topographic ridges such as the Reykjanes Ridge or the Rockall Plateau. Mid-basin northward advection pathways from the northeastern Labrador Sea into the Irminger Sea and from the Mid-Atlantic Ridge region into the Iceland Basin are well-resolved. An eastward flow is present across the southern boundary of the subpolar gyre near 52°N, the latitude of the Charlie Gibbs Fracture Zone (CGFZ). The mid-depth EKE field resembles most of the satellite-derived surface EKE field. However, noticeable differences exist along the northward advection pathways in the Irminger Sea and the Iceland Basin, where the deep EKE exceeds the surface EKE field. Further, the ratio between mean flow and the square root of the EKE, the Peclet number, reveals distinct advection-dominated regions as well as basin-interior regimes in which mixing is prevailing.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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  • 3
    Publication Date: 2019-05-23
    Description: Two consecutive summer upwelling events, each lasting for less than 24 h, were surveyed in high temporal and vertical resolution close to the Boknis Eck time-series station (BE) in the western Belt Sea (Baltic Sea) in summer 2010 with an autonomous glider. Driven only by moderate offshore winds both events resulted in more than 5 K cooling of surface waters, while only for the second event were significant irreversible changes in the vertical stratification observed. Generalizing the glider survey observations with hourly wind data from nearby meteorological stations, it is found that upwelling in the BE area occurs for wind directions between 190 to 260° and wind speed exceeding 4 m s−1. Based on these thresholds the wind-induced summer (June to September) upwelling conditions in the BE area for the period 1982 to 2012 are reconstructed. On average about 18 days of upwelling favourable wind conditions are found for the four summer months, with significant interannual variability ranging from 7.7 days (2006) to more than 28 days (1985). By aligning upwelling favourable wind conditions with the monthly BE surveys it is found that extreme anomalies in BE surveys follow extended periods of upwelling favourable winds.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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  • 4
    Publication Date: 2022-01-31
    Description: River water is the main source of dissolved organic carbon (DOC) in the Arctic Ocean. DOC plays an important role in the Arctic carbon cycle, and its export from land to sea is expected to increase as ongoing climate change accelerates permafrost thaw. However, transport pathways and transformation of DOC in the land-to-ocean transition are mostly unknown. We collected DOC and aCDOM(λ) samples from 11 expeditions to river, coastal and offshore waters and present a new DOC–aCDOM(λ) model for the fluvial–marine transition zone in the Laptev Sea. The aCDOM(λ) characteristics revealed that the dissolved organic matter (DOM) in samples of this dataset are primarily of terrigenous origin. Observed changes in aCDOM(443) and its spectral slopes indicate that DOM is modified by microbial and photo-degradation. Ocean colour remote sensing (OCRS) provides the absorption coefficient of coloured dissolved organic matter (aCDOM(λ)sat) at λ=440 or 443 nm, which can be used to estimate DOC concentration at high temporal and spatial resolution over large regions. We tested the statistical performance of five OCRS algorithms and evaluated the plausibility of the spatial distribution of derived aCDOM(λ)sat. The OLCI (Sentinel-3 Ocean and Land Colour Instrument) neural network swarm (ONNS) algorithm showed the best performance compared to in situ aCDOM(440) (r2=0.72). Additionally, we found ONNS-derived aCDOM(440), in contrast to other algorithms, to be partly independent of sediment concentration, making ONNS the most suitable aCDOM(λ)sat algorithm for the Laptev Sea region. The DOC–aCDOM(λ) model was applied to ONNS-derived aCDOM(440), and retrieved DOC concentration maps showed moderate agreement to in situ data (r2=0.53). The in situ and satellite-retrieved data were offset by up to several days, which may partly explain the weak correlation for this dynamic region. Satellite-derived surface water DOC concentration maps from Medium Resolution Imaging Spectrometer (MERIS) satellite data demonstrate rapid removal of DOC within short time periods in coastal waters of the Laptev Sea, which is likely caused by physical mixing and different types of degradation processes. Using samples from all occurring water types leads to a more robust DOC–aCDOM(λ) model for the retrievals of DOC in Arctic shelf and river waters.
    Type: Article , PeerReviewed
    Format: text
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  • 5
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2017. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Bulletin of the American Meteorological Society 98 (2017): 737-752, doi:10.1175/BAMS-D-16-0057.1.
    Description: For decades oceanographers have understood the Atlantic meridional overturning circulation (AMOC) to be primarily driven by changes in the production of deep-water formation in the subpolar and subarctic North Atlantic. Indeed, current Intergovernmental Panel on Climate Change (IPCC) projections of an AMOC slowdown in the twenty-first century based on climate models are attributed to the inhibition of deep convection in the North Atlantic. However, observational evidence for this linkage has been elusive: there has been no clear demonstration of AMOC variability in response to changes in deep-water formation. The motivation for understanding this linkage is compelling, since the overturning circulation has been shown to sequester heat and anthropogenic carbon in the deep ocean. Furthermore, AMOC variability is expected to impact this sequestration as well as have consequences for regional and global climates through its effect on the poleward transport of warm water. Motivated by the need for a mechanistic understanding of the AMOC, an international community has assembled an observing system, Overturning in the Subpolar North Atlantic Program (OSNAP), to provide a continuous record of the transbasin fluxes of heat, mass, and freshwater, and to link that record to convective activity and water mass transformation at high latitudes. OSNAP, in conjunction with the Rapid Climate Change–Meridional Overturning Circulation and Heatflux Array (RAPID–MOCHA) at 26°N and other observational elements, will provide a comprehensive measure of the three-dimensional AMOC and an understanding of what drives its variability. The OSNAP observing system was fully deployed in the summer of 2014, and the first OSNAP data products are expected in the fall of 2017.
    Description: The authors gratefully acknowledge financial support from the U.S. National Science Foundation (NSF; OCE-1259102, OCE-1259103, OCE-1259618, OCE-1258823, OCE-1259210, OCE-1259398, OCE-0136215, and OCE-1005697); the U.S. National Aeronautics and Space Administration (NASA); the U.S. National Oceanic and Atmospheric Administration (NOAA); the WHOI Ocean and Climate Change Institute (OCCI), the WHOI Independent Research and Development (IRD) Program, and the WHOI Postdoctoral Scholar Program; the U.K. Natural Environment Research Council (NERC; NE/K010875/1, NE/K010700/1, R8-H12-85, FASTNEt NE/I030224/1, NE/K010972/1, NE/K012932/1, and NE/M018024/1); the European Union Seventh Framework Programme (NACLIM project, 308299 and 610055); the German Federal Ministry and Education German Research RACE Program; the Natural Sciences and Engineering Research Council of Canada (NSERC; RGPIN 227438-09, RGPIN 04357, and RG-PCC 433898); Fisheries and Oceans Canada; the National Natural Science Foundation of China (NSFC; 41521091, U1406401); the Fundamental Research Funds for the Central Universities of China; the French Research Institute for Exploitation of the Sea (IFREMER); the French National Center for Scientific Research (CNRS); the French National Institute for Earth Sciences and Astronomy (INSU); the French national program LEFE; and the French Oceanographic Fleet (TGIR FOF).
    Description: 2017-10-24
    Repository Name: Woods Hole Open Access Server
    Type: Article
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