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  • 11
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    Factors influencing the meridional width of the equatorial deep jets (2023)
    Copernicus Publications (EGU)
    Details
    Publication Date: 2024-02-07
    Description: Equatorial deep jets (EDJs) are vertically alternating, stacked zonal currents that flow along the Equator in all three ocean basins at intermediate depth. Their structure can be described quite well by the sum of high-baroclinic-mode equatorial Kelvin and Rossby waves. However, the EDJ meridional width is larger by a factor of 1.5 than inviscid theory predicts for such waves. Here, we use a set of idealised model configurations representing the Atlantic Ocean to investigate the contributions of different processes to the enhanced EDJ width. Corroborated by the analysis of shipboard velocity sections, we show that widening of the EDJs by momentum loss due to irreversible mixing or other processes contributes more to their enhanced time mean width than averaging over meandering of the jets. Most of the widening due to meandering can be attributed to the strength of intraseasonal variability in the jets' depth range, suggesting that the jets are meridionally advected by intraseasonal waves. A slightly weaker connection to intraseasonal variability is found for the EDJ widening by momentum loss. These results enhance our understanding of the dynamics of the EDJs and, more generally, of equatorial waves in the deep ocean.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 12
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    Internally generated circulation and variability in the tropical Atlantic Ocean (2021)
    Details
    Publication Date: 2024-02-07
    Description: The thesis investigates different dynamical and statistical aspects of the Atlantic Equatorial Deep Jets (EDJ) and the central Atlantic Equatorial Intermediate Current System (EICS). One of these is the maintenance mechanism of the EDJ and the central EICS. It is shown that the convergence of the meridional flux of intraseasonal zonal momentum that is associated with the deformation of intraseasonal waves by the equatorial currents can maintain them against dissipation in an idealised ocean model of the tropical Atlantic. Another point that is investigated is the energy transfer between the EDJ and the central EICS. It is shown that the interannually varying EDJ nonlinearly transfer energy to the time mean currents at intermediate depth, strenghtening the central EICS in the western part of the basin and weakening or reversing it in the eastern basin. In addition, a new comprehensive analysis of the spatial and temporal scales of the Atlantic EDJ from Argo float observations is presented, which adds significantly to the available knowledge about the appearance of the Atlantic EDJ in the real ocean. Furthermore, the origin of the enhanced meridional width of the EDJ compared to their theoretically expected width is investigated in a series of idealised ocean models. It is shown that instantaneous meridional widening of the EDJ due to stronger mixing of momentum than of tracers plays a larger role than averaging over intraseasonal meandering of the EDJ.
    Type: Thesis , NonPeerReviewed , info:eu-repo/semantics/other
    Format: text
    Location Call Number Limitation Availability
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    OceanRep: Thesis - not published by a publisher
  • 13
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    ICON-Sapphire: simulating the components of the Earth system and their interactions at kilometer and subkilometer scales (2023)
    Copernicus Publications (EGU)
    Details
    Publication Date: 2024-02-07
    Description: State-of-the-art Earth system models typically employ grid spacings of O(100 km), which is too coarse to explicitly resolve main drivers of the flow of energy and matter across the Earth system. In this paper, we present the new ICON-Sapphire model configuration, which targets a representation of the components of the Earth system and their interactions with a grid spacing of 10 km and finer. Through the use of selected simulation examples, we demonstrate that ICON-Sapphire can (i) be run coupled globally on seasonal timescales with a grid spacing of 5 km, on monthly timescales with a grid spacing of 2.5 km, and on daily timescales with a grid spacing of 1.25 km; (ii) resolve large eddies in the atmosphere using hectometer grid spacings on limited-area domains in atmosphere-only simulations; (iii) resolve submesoscale ocean eddies by using a global uniform grid of 1.25 km or a telescoping grid with the finest grid spacing at 530 m, the latter coupled to a uniform atmosphere; and (iv) simulate biogeochemistry in an ocean-only simulation integrated for 4 years at 10 km. Comparison of basic features of the climate system to observations reveals no obvious pitfalls, even though some observed aspects remain difficult to capture. The throughput of the coupled 5 km global simulation is 126 simulated days per day employing 21 % of the latest machine of the German Climate Computing Center. Extrapolating from these results, multi-decadal global simulations including interactive carbon are now possible, and short global simulations resolving large eddies in the atmosphere and submesoscale eddies in the ocean are within reach.
    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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