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  • AMS (American Meteorological Society)  (3)
  • 2015-2019  (3)
  • 2018  (3)
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  • 2015-2019  (3)
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  • 1
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    Influences of Pacific Climate Variability on Decadal Subsurface Ocean Heat Content Variations in the Indian Ocean (2018)
    AMS (American Meteorological Society)
    In:  Journal of Climate, 31 (10). pp. 4157-4174.
    Details
    Publikationsdatum: 2021-02-08
    Beschreibung: Decadal variabilities in Indian Ocean subsurface ocean heat content (OHC; 50–300 m) since the 1950s are examined using ocean reanalyses. This study elaborates on how Pacific variability modulates the Indian Ocean on decadal time scales through both oceanic and atmospheric pathways. High correlations between OHC and thermocline depth variations across the entire Indian Ocean Basin suggest that OHC variability is primarily driven by thermocline fluctuations. The spatial pattern of the leading mode of decadal Indian Ocean OHC variability closely matches the regression pattern of OHC on the interdecadal Pacific oscillation (IPO), emphasizing the role of the Pacific Ocean in determining Indian Ocean OHC decadal variability. Further analyses identify different mechanisms by which the Pacific influences the eastern and western Indian Ocean. IPO-related anomalies from the Pacific propagate mainly through oceanic pathways in the Maritime Continent to impact the eastern Indian Ocean. By contrast, in the western Indian Ocean, the IPO induces wind-driven Ekman pumping in the central Indian Ocean via the atmospheric bridge, which in turn modifies conditions in the southwestern Indian Ocean via westward-propagating Rossby waves. To confirm this, a linear Rossby wave model is forced with wind stresses and eastern boundary conditions based on reanalyses. This linear model skillfully reproduces observed sea surface height anomalies and highlights both the oceanic connection in the eastern Indian Ocean and the role of wind-driven Ekman pumping in the west. These findings are also reproduced by OGCM hindcast experiments forced by interannual atmospheric boundary conditions applied only over the Pacific and Indian Oceans, respectively.
    Materialart: Article , PeerReviewed
    Format: text
    DOI: 10.1175/JCLI-D-17-0654.1
    Standort Signatur Einschränkungen Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    OceanRep: Artikel in einer Fachzeitschrift - begutachtet
  • 2
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    Instability-Driven Benthic Storms Below the Separated Gulf Stream and the North Atlantic Current in a High-Resolution Ocean Model (2018)
    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 48 . pp. 2283-2303.
    Details
    Publikationsdatum: 2021-02-08
    Beschreibung: Benthic storms are important for both the energy budget of the ocean and for sediment resuspension and transport. Using 30 years of output from a high-resolution model of the North Atlantic, it is found that most of the benthic storms in the model occur near the western boundary in association with the Gulf Stream and the North Atlantic Current, in regions that are generally co-located with the peak near-bottom eddy kinetic energy. A common feature are meander troughs in the near-surface jets that are accompanied by deep low pressure anomalies spinning up deep cyclones with near-bottom velocities of up to more than 0.5 m/s. A case study of one of these events shows the importance of both baroclinic and barotropic instability of the jet, with energy being extracted from the jet in the upstream part of the meander trough and partly returned to the jet in the downstream part of the meander trough. This motivates examining the 30-year time mean of the energy transfer from the (annual mean) background flow into the eddy kinetic energy. This quantity is shown to be co-located well with the region in which benthic storms and large increases in deep cyclonic relative vorticity occur most frequently, suggesting an important role for mixed barotropic-baroclinic instability driven cyclogenesis in generating benthic storms throughout the model simulation. Regions of largest energy transfer and most frequent benthic storms are found to be the Gulf Stream west of the New England Seamounts and the North Atlantic Current near Flemish Cap.
    Materialart: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1175/JPO-D-17-0261.1
    Standort Signatur Einschränkungen Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    OceanRep: Artikel in einer Fachzeitschrift - begutachtet
  • 3
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    Eddy diffusivity estimates from Lagrangian trajectories simulated with ocean models and surface drifter data - a case study for the greater Agulhas system (2018)
    AMS (American Meteorological Society)
    Details
    Publikationsdatum: 2023-01-31
    Beschreibung: The Lagrangian analysis of sets of particles advected with the flow fields of ocean models are used to study connectivity, i.e. exchange pathways, timescales and volume transports, between distinct oceanic regions. One important factor influencing the dispersion of fluid particles and hence connectivity is the Lagrangian eddy diffusivity, which quantifies the influence of turbulent processes on the rate of particle dispersal. Due to spatial and temporal discretization, turbulence is not fully resolved in modelled velocities, and the concept of eddy diffusivity is used to parametrize the impact of unresolved processes. However, the relations between observational- and model-based Lagrangian eddy diffusivity estimates as well as eddy parameterizations are not clear. This study presents an analysis of the spatially variable near-surface lateral eddy diffusivity estimates obtained from Lagrangian trajectories simulated with 5-day mean velocities from an eddy-resolving ocean model (INALT01) for the Agulhas system. INALT01 features diffusive regimes for dynamically different regions, some of which exhibit strong suppression of eddy mixing by mean flow, and is consistent with the pattern and magnitude of drifter-based eddy diffusivity estimates. Using monthly-mean velocities decreases the estimated diffusivities less than eddy kinetic energy, supporting the idea that large and persistent eddy features dominate eddy diffusivities. For a non-eddying ocean model (ORCA05), Lagrangian eddy diffusivities are greatly reduced, in particular when the Gent and McWilliams parameterization of mesoscale eddies is employed.
    Materialart: Article , PeerReviewed
    Format: text
    Format: text
    Standort Signatur Einschränkungen Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    OceanRep: Artikel in einer Fachzeitschrift - begutachtet
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