scholarly journals Seasonal variability of eddy kinetic energy in a global high-resolution ocean model

2015 ◽  
Vol 42 (21) ◽  
pp. 9379-9386 ◽  
Author(s):  
Jan K. Rieck ◽  
Claus W. Böning ◽  
Richard J. Greatbatch ◽  
Markus Scheinert
Keyword(s):  
High Resolution ◽  
Kinetic Energy ◽  
Seasonal Variability ◽  
Ocean Model ◽  
Eddy Kinetic Energy

scholarly journals Numerical simulation and decomposition of kinetic energy in the Central Mediterranean: insight on mesoscale circulation and energy conversion

Ocean Science ◽  
2011 ◽  
Vol 7 (4) ◽  
pp. 503-519 ◽  
Author(s):  
R. Sorgente ◽  
A. Olita ◽  
P. Oddo ◽  
L. Fazioli ◽  
A. Ribotti
Keyword(s):  
Numerical Simulation ◽  
Kinetic Energy ◽  
Energy Conversion ◽  
Ocean Model ◽  
Eddy Kinetic Energy ◽  
Tyrrhenian Sea ◽  
Central Mediterranean ◽  
Baroclinic Energy Conversion ◽  
Sicily Channel ◽  
Mean Kinetic Energy

Abstract. The spatial and temporal variability of eddy and mean kinetic energy of the Central Mediterranean region has been investigated, from January 2008 to December 2010, by mean of a numerical simulation mainly to quantify the mesoscale dynamics and their relationships with physical forcing. In order to understand the energy redistribution processes, the baroclinic energy conversion has been analysed, suggesting hypotheses about the drivers of the mesoscale activity in this area. The ocean model used is based on the Princeton Ocean Model implemented at 1/32° horizontal resolution. Surface momentum and buoyancy fluxes are interactively computed by mean of standard bulk formulae using predicted model Sea Surface Temperature and atmospheric variables provided by the European Centre for Medium Range Weather Forecast operational analyses. At its lateral boundaries the model is one-way nested within the Mediterranean Forecasting System operational products. The model domain has been subdivided in four sub-regions: Sardinia channel and southern Tyrrhenian Sea, Sicily channel, eastern Tunisian shelf and Libyan Sea. Temporal evolution of eddy and mean kinetic energy has been analysed, on each of the four sub-regions, showing different behaviours. On annual scales and within the first 5 m depth, the eddy kinetic energy represents approximately the 60 % of the total kinetic energy over the whole domain, confirming the strong mesoscale nature of the surface current flows in this area. The analyses show that the model well reproduces the path and the temporal behaviour of the main known sub-basin circulation features. New mesoscale structures have been also identified, from numerical results and direct observations, for the first time as the Pantelleria Vortex and the Medina Gyre. The classical kinetic energy decomposition (eddy and mean) allowed to depict and to quantify the permanent and fluctuating parts of the circulation in the region, and to differentiate the four sub-regions as function of relative and absolute strength of the mesoscale activity. Furthermore the Baroclinic Energy Conversion term shows that in the Sardinia Channel the mesoscale activity, due to baroclinic instabilities, is significantly larger than in the other sub-regions, while a negative sign of the energy conversion, meaning a transfer of energy from the Eddy Kinetic Energy to the Eddy Available Potential Energy, has been recorded only for the surface layers of the Sicily Channel during summer.

scholarly journals Numerical simulation and decomposition of kinetic energies in the Central Mediterranean Sea: insight on mesoscale circulation and energy conversion

2011 ◽  
Vol 8 (3) ◽  
pp. 1161-1214 ◽  
Author(s):  
R. Sorgente ◽  
A. Olita ◽  
P. Oddo ◽  
L. Fazioli ◽  
A. Ribotti
Keyword(s):  
Numerical Simulation ◽  
Kinetic Energy ◽  
Energy Conversion ◽  
Mediterranean Sea ◽  
Ocean Model ◽  
Eddy Kinetic Energy ◽  
Central Mediterranean ◽  
Central Mediterranean Sea ◽  
Baroclinic Energy Conversion ◽  
Mean Kinetic Energy

Abstract. The spatial and temporal variability of eddy and mean kinetic energy of the Central Mediterranean Sea has been investigated, from January 2008 to December 2010, by mean of a numerical simulation mainly to quantify the mesoscale dynamics and their relationships with physical forcing. In order to understand the energy redistribution processes, the baroclinic energy conversion has been analysed, suggesting hypotheses about the drivers of the mesoscale activity in this area. The ocean model used is based on the Princeton Ocean Model implemented at 1/32° horizontal resolution. Surface momentum and buoyancy fluxes are interactively computed by mean of standard bulk formulae using predicted model Sea Surface Temperature and atmospheric variables provided by the European Centre for Medium Range Weather Forecast operational analyses. At its lateral boundaries the model is one-way nested within the Mediterranean Forecasting System operational products. The model domain has been subdivided in four sub-regions: Sardinia channel and southern Tyrrhenian Sea, Sicily channel, eastern Tunisian shelf and Libyan Sea. Temporal evolution of eddy and mean kinetic energy has been analysed, on each of the four sub-regions composing the model domain, showing different behaviours. On annual scales and within the first 5 m depth, the eddy kinetic energy represents approximately the 60 % of the total kinetic energy over the whole domain, confirming the strong mesoscale nature of the surface current flows in this area. The analyses show that the model well reproduces the path and the temporal behaviour of the main known sub-basin circulation features. New mesoscale structures have been also identified, from numerical results and direct observations, for the first time as the Pantelleria Vortex and the Medina Gyre. The classical the kinetic energy decomposition (eddy and mean) allowed to depict and to quantify the stable and fluctuating parts of the circulation in the region, and to differentiate the four sub-regions as function of relative and absolute strength of the mesoscale activity. Furthermore the Baroclinic Energy Conversion term shows that in the Sardinia Channel the mesoscale activity, due to baroclinic instabilities, is significantly larger than in the other sub-regions, while a negative sign of the energy conversion, meaning a transfer of energy from the Eddy Kinetic Energy to the Eddy Available Potential Energy, has been recorded only for the surface layers of the Sicily Channel during summer.

scholarly journals Instability-Driven Benthic Storms below the Separated Gulf Stream and the North Atlantic Current in a High-Resolution Ocean Model

2018 ◽  
Vol 48 (10) ◽  
pp. 2283-2303 ◽  
Author(s):  
René Schubert ◽  
Arne Biastoch ◽  
Meghan F. Cronin ◽  
Richard J. Greatbatch
Keyword(s):  
Energy Transfer ◽  
High Resolution ◽  
Kinetic Energy ◽  
North Atlantic ◽  
Gulf Stream ◽  
Eddy Kinetic Energy ◽  
North Atlantic Current ◽  
The North ◽  
The North Atlantic ◽  
Atlantic Current

AbstractBenthic 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 collocated with the peak near-bottom eddy kinetic energy. A common feature is 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−1. 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-yr time mean of the energy transfer from the (annual mean) background flow into the eddy kinetic energy. This quantity is shown to be collocated 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 the 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.

scholarly journals Impact of Variable-Resolution Meshes on Midlatitude Baroclinic Eddies Using CAM-MPAS-A

2014 ◽  
Vol 142 (11) ◽  
pp. 4256-4268 ◽  
Author(s):  
Sara A. Rauscher ◽  
Todd D. Ringler
Keyword(s):  
High Resolution ◽  
Kinetic Energy ◽  
Real World ◽  
National Science Foundation ◽  
Eddy Kinetic Energy ◽  
Department Of Energy ◽  
Variable Resolution ◽  
Community Atmosphere Model ◽  
Model Dynamics ◽  
Sea Surface Temperature Anomalies

Abstract The effects of a variable-resolution mesh on simulated midlatitude baroclinic eddies in idealized settings are examined. Both aquaplanet and Held–Suarez experiments are performed using the Model for Prediction Across Scales-Atmosphere (MPAS-A) hydrostatic dynamical core implemented within the National Science Foundation–Department of Energy (NSF–DOE) Community Atmosphere Model (CAM-MPAS-A). In the real world, midlatitude eddy activity is organized by orography, land–sea contrasts, and sea surface temperature anomalies. In these zonally symmetric idealized settings, transients should have an equal probability of occurring at any longitude. However, the use of a variable-resolution mesh with a circular high-resolution region centered at 30°N results in a maximum in eddy kinetic energy on the eastern side and downstream of this high-resolution region in both aquaplanet and Held–Suarez CAM-MPAS-A simulations. The presence of a geographically confined maximum in both simulations suggests this response is mainly attributable to CAM-MPAS-A’s ability to resolve eddies via the model dynamics as resolution increases. However, in the aquaplanet simulation, a secondary maximum in eddy kinetic energy is present, which is probably linked to the resolution dependencies of the CAM physics. These mesh responses must be considered when interpreting real-world variable-resolution CAM-MPAS-A simulations, particularly in climate change experiments.

A synthesis of upper ocean geostrophic kinetic energy spectra from a global submesoscale permitting simulation

2021 ◽  
Author(s):  
Hemant Khatri ◽  
Stephen Griffies ◽  
Takaya Uchida ◽  
Han Wang ◽  
Dimitris Menemenlis
Keyword(s):  
Kinetic Energy ◽  
Mixed Layer ◽  
Seasonal Variability ◽  
Ocean Model ◽  
Global Ocean ◽  
Upper Ocean ◽  
Late Winter ◽  
Second Phase ◽  
Ocean Turbulence ◽  
Two Phases

<p>In the upper ocean, submesoscale turbulence shows seasonal variability and is pronounced in winter. We analyze geostrophic KE spectra in a submesoscale-permitting global ocean model to study the seasonal variability in the upper ocean turbulence. Submesoscale processes peak in winter and, consequently, geostrophic kinetic energy (KE) spectra tend to be relatively shallow in winter (<em>k</em><sup>-2</sup>) with steeper spectra in summer (<em>k</em><sup>-3</sup>). The roles of frontogenesis processes and mixed-layer instabilities in submesoscale turbulence and their effects on the evolution of KE spectra over an annual cycle are discussed. It is shown that this transition in KE spectral scaling has two phases. In the first phase (late autumn), KE spectra show a presence of two spectral regimes: <em>k</em><sup>-3</sup> scaling in mesoscales (100-300 km) and <em>k</em><sup>-2</sup> scaling in submesoscales (< 50 km), indicating the coexistence of QG, surface-QG, and frontal dynamics. In the second phase (late winter), mixed-layer instabilities convert available potential energy into KE, which cascades upscale leading to flattening of the KE spectra at larger scales, and <em>k</em><sup>-2</sup> power-law develops in mesoscales too.</p>

scholarly journals On the seasonal variability of eddy kinetic energy in the Gulf Stream region

2008 ◽  
Vol 35 (24) ◽  
Author(s):  
Xiaoming Zhai ◽  
Richard J. Greatbatch ◽  
Jan-Dirk Kohlmann
Keyword(s):  
Kinetic Energy ◽  
Gulf Stream ◽  
Seasonal Variability ◽  
Eddy Kinetic Energy

Generation and seasonal variability of eddy kinetic energy in the central Indian Ocean

2021 ◽  
Author(s):  
Georgy I. Shapiro ◽  
Jose Maria Gonzalez-Ondina
Keyword(s):  
Indian Ocean ◽  
Kinetic Energy ◽  
Seasonal Variability ◽  
Open Ocean ◽  
Eddy Kinetic Energy ◽  
Horizontal Shear ◽  
Data Set ◽  
Central Indian Ocean ◽  
The Indian Ocean ◽  
Meso Scale

<p>The breakthrough in our knowledge of ocean eddies came with the results of the POLYGON-67 experiment in the central Indian Ocean carried out in January-April 1967 (see Koshlyakov et al, 2016). It was the first direct and unambiguous observation that proved an earlier hypothesis by V. B. Shtockman of the existence of mesoscale eddies in open ocean, not only next to strong jet-stream currents. Now it is well known that the currents in open ocean are almost everywhere dominated by meso-scale eddies also known as synoptic eddies (Robinson, 1983). POLYGON-67 experiment covered a rectangle bounded by 10-15°N and 63-66.5°E. The purpose of this work is to analyse the seasonal variability of meso-scale eddy activity in the area covered by POLYGON-67 using a modern and comprehensive data set produced by an operational data assimilation model over a period from 1998 to 2017.</p><p>The 20-year long eddy resolving reanalysis of velocity fields in the Indian Ocean allows the study of seasonal variability, dynamics and generating mechanisms of eddy kinetic energy (EKE) in the tropical Indian Ocean, including the area covered by the original survey of POLYGON-67. In contrast to some other areas of the World Ocean, the EKE seasonality shows two maxima, the large one in April and the secondary one in October. The main mechanism of EKE generation is the barotropic instability which is evidenced by high correlation between EKE and enstrophy of large-scale currents, representing the strength of horizontal shear. It is found that the main contributor to the EKE variability within POLYGON-67 area is the advection of EKE across the boundaries during January-October, while the local generation has a comparable magnitude during August-December. The direction and strength of surface currents is consistent with the monsoon wind pattern in the area.</p><p>References</p><p>Koshlyakov, M.N., Morozov, E.G., and Neiman, V.G., 2016. Historical findings of the Russian physical oceanographers in the Indian Ocean. Geoscience Letters, 3:19; doi:10.1186/s40562-016-0051-6</p><p>Robinson, A.R. (Ed), 1983. Eddies in Marine Science. Springer, ISBN 978-3-642-69003-7, 612p.</p>

scholarly journals Seasonal and regional variations of sinking in the subpolar North Atlantic from a high-resolution ocean model

Ocean Science ◽  
2019 ◽  
Vol 15 (4) ◽  
pp. 1033-1053 ◽  
Author(s):  
Juan-Manuel Sayol ◽  
Henk Dijkstra ◽  
Caroline Katsman
Keyword(s):  
High Resolution ◽  
North Atlantic ◽  
Seasonal Variability ◽  
Ocean Model ◽  
Meridional Overturning Circulation ◽  
Boundary Current ◽  
Meridional Transport ◽  
Marginal Seas ◽  
Complex Picture ◽  
Mean Fields

Abstract. Previous studies have indicated that most of the net sinking associated with the downward branch of the Atlantic Meridional Overturning Circulation (AMOC) must occur near the subpolar North Atlantic boundaries. In this work we have used monthly mean fields of a high-resolution ocean model (0.1∘ at the Equator) to quantify this sinking. To this end we have calculated the Eulerian net vertical transport (W∑) from the modeled vertical velocities, its seasonal variability, and its spatial distribution under repeated climatological atmospheric forcing conditions. Based on this simulation, we find that for the whole subpolar North Atlantic W∑ peaks at about −14 Sv at a depth of 1139 m, matching both the mean depth and the magnitude of the meridional transport of the AMOC at 45∘ N. It displays a seasonal variability of around 10 Sv. Three sinking regimes are identified according to the characteristics of the accumulated W∑ with respect to the distance to the shelf: one within the first 90 km and onto the bathymetric slope at around the peak of the boundary current speed (regime I), the second between 90 and 250 km covering the remainder of the shelf where mesoscale eddies exchange properties (momentum, heat, mass) between the interior and the boundary (regime II), and the third at larger distances from the shelf where W∑ is mostly driven by the ocean's interior eddies (regime III). Regimes I and II accumulate ∼90 % of the total sinking and display smaller seasonal changes and spatial variability than regime III. We find that such a distinction in regimes is also useful to describe the characteristics of W∑ in marginal seas located far from the overflow areas, although the regime boundaries can shift a few tens of kilometers inshore or offshore depending on the bathymetric slope and shelf width of each marginal sea. The largest contributions to the sinking come from the Labrador Sea, the Newfoundland region, and the overflow regions. The magnitude, seasonal variability, and depth at which W∑ peaks vary for each region, thus revealing a complex picture of sinking in the subpolar North Atlantic.

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