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  • Elsevier  (2)
  • AGU (American Geophysical Union)  (1)
  • AMS (American Meteorological Society)  (1)
  • 2000-2004  (4)
Document type
Publisher
Years
Year
  • 1
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    Variational assimilation of SSH variability from TOPEX/POSEIDON and ERSI into an eddy-permitting model of the North Atlantic (2003)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 108 (C3). p. 3092.
    Details
    Publication Date: 2019-04-04
    Description: A first step for improving the climatological state of high‐resolution general circulation models by means of data assimilation is presented. A method developed for the assimilation of statistical characteristics into chaotic ocean models is applied to assimilate SSH variability from TOPEX/POSEIDON and ERS1 in association with temperature and salinity from the World Ocean Atlas 1997 in order to estimate the underlying mean circulation. The method requires a parameterization of SSH variability which derives from the approach of Green and Stone. By estimating initial conditions for temperature and salinity, a mean state is achieved which, although not fully consistent with the altimetric and climatological data, is markedly improved on time scales of one year in comparison to the control run. The assimilation of SSH variability data introduces complementary information about the main frontal structures consistent with climatological observations. The state is however not an equilibrium state and returns back to the first guess quasi‐equilibrium state for longer integration periods.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2001JC000982
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Circulation Characteristics in Three Eddy-Permitting Models of the North Atlantic (2001)
    Elsevier
    In:  Progress in Oceanography, 48/2-3 . pp. 123-162.
    Details
    Publication Date: 2016-10-07
    Description: A systematic intercomparison of three realistic eddy-permitting models of the North Atlantic circulation has been performed. The models use different concepts for the discretization of the vertical coordinate, namely geopotential levels, isopycnal layers, terrain-following (sigma) coordinates, respectively. Although these models were integrated under nearly identical conditions, the resulting large-scale model circulations show substantial differences. The results demonstrate that the large-scale thermohaline circulation is very sensitive to the model representation of certain localised processes, in particular to the amount and water mass properties of the overflow across the Greenland–Scotland region, to the amount of mixing within a few hundred kilometers south of the sills, and to several other processes at small or sub-grid scales. The different behaviour of the three models can to a large extent be explained as a consequence of the different model representation of these processes.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/S0079-6611(01)00003-9
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Assimilation of Altimetric Data into an Eddy-Permitting Model of the North Atlantic (2001)
    Elsevier
    In:  Progress in Oceanography, 48 (2-3). pp. 313-315.
    Details
    Publication Date: 2019-09-23
    Description: This paper shows that the mean flow of an eddy-permitting model can be altered by assimilation of surface height variability, providing that information about the mean sea surface is included, using an adaption of a statistical–dynamical method devised by Oschlies and Willebrand. We show that for a restricted depth range (about 1000 m), dynamical knowledge can make up for the null space present in surface data whose temporal extent may be too short to distinguish between vertical modes. The lack of an accurate geoid has meant that most assimilation methods, while representing variability well, have been unable to modify the mean flow to any extent. However, we show that by including several approximate forms for the mean sea surface, the mean interior flow in the upper kilometer can be rapidly adjusted towards reality by the assimilation, with the location of major current systems moved by hundreds of kilometers.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/S0079-6611(01)00009-X
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Mechanism of interannual to decadal variability of the North Atlantic circulation (2001)
    AMS (American Meteorological Society)
    Details
    Publication Date: 2022-03-10
    Description: A model of the Atlantic Ocean was forced with decadal-scale time series of surface fluxes taken from the National Centers for Environmental Prediction–National Center for Atmospheric Research reanalysis. The bulk of the variability of the oceanic circulation is found to be related to the North Atlantic oscillation (NAO). Both realistic experiments and idealized sensitivity studies with the model show a fast (intraseasonal timescale) barotropic response and a delayed (timescale about 6–8 yr) baroclinic oceanic response to the NAO. The fast response to a high NAO constitutes a barotropic anticyclonic circulation anomaly near the subpolar front with a substantial decrease of the northward heat transport and an increase of northward heat transport in the subtropics due to changes in Ekman transport. The delayed response is an increase in subpolar heat transport due to enhanced meridional overturning and due to a spinup of the subpolar gyre. The corresponding subpolar and subtropical heat content changes could in principle act as an immediate positive feedback and a delayed negative feedback to the NAO.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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