Mesoscale SST–wind stress coupling in the Peru–Chile current system: Which mechanisms drive its seasonal variability?

Oerder, Véra; Colas, François; Échevin, Vincent; Masson, Sébastien; Hourdin, Christophe; Jullien, Swen; Madec, Gurvan; Lemarié, Florian

doi:10.1007/s00382-015-2965-7

Cited by 37 publications

(53 citation statements)

References 83 publications

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“…Our results show that the mesoscale‐induced wind stress intensity variations above the coherent eddies can be approximated by the linear superposition of the SST‐induced and the current‐induced effects equation . The SST‐induced term (

s_{1}^{τ} S S T'

) dominates the current‐induced effect (

s_{2}^{τ} \overset{true\to}{v_{s}^{o}}' . \frac{\overset{true\to}{τ_{s}}}{‖ \overset{true\to}{τ_{s}} ‖}

), which explains why relation (8) is clearly identified in the South‐East Pacific (Oerder et al, ) and other regions (e.g., O'Neill et al, ). On the other hand, the current‐stress interaction has a stronger impact on the wind stress direction, leading to a larger wind stress curl anomaly above eddies than the SST‐induced effect.…”

Section: Discussionmentioning

confidence: 99%

“…A detailed comparison of the modeled and observed atmosphere and ocean dynamics in the South East Pacific can be found in Oerder et al (). The surface current velocity and wind stress averaged over the 2003–2008 period are shown on Figure .…”

Section: Methodsmentioning

confidence: 99%

“…Indeed, this coupled model configuration has been shown to realistically capture mesoscale air‐sea interactions (Oerder et al, ). The wind stress modulation by the surface current is characterized by a linear relation between wind stress curl and surface current vorticity with negative correlation (Rooth & Xie, ).…”

Section: Methodsmentioning

confidence: 99%

“…The underlying mechanism may vary with the studied region. For example, in the South East Pacific, it has been shown that these surface wind stress anomalies result from atmospheric vertical mixing modifications due to mesoscale SST anomalies (Oerder et al, ). Such SST‐induced wind stress modulation above SST fronts creates wind stress curl structures proportional to the crosswind SST gradient (Chelton et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Impacts of the Mesoscale Ocean‐Atmosphere Coupling on the Peru‐Chile Ocean Dynamics: The Current‐Induced Wind Stress Modulation

et al. 2018

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The ocean dynamical responses to the surface current‐wind stress interaction at the oceanic mesoscale are investigated in the South‐East Pacific using a high‐resolution regional ocean‐atmosphere coupled model. Two simulations are compared: one includes the surface current in the wind stress computation while the other does not. In the coastal region, absolute wind velocities are different between the two simulations but the wind stress remains very similar. As a consequence, the mean regional oceanic circulation is almost unchanged. On the contrary, the mesoscale activity is strongly reduced when taking into account the effect of the surface current on the wind stress. This is caused by a weakening of the eddy kinetic energy generation near the coast by the wind work and to intensified offshore eddy damping. We show that, above coherent eddies, the current‐stress interaction generates eddy damping through Ekman pumping and eddy kinetic energy dissipation through wind work. This alters significantly the coherent eddy vertical structures compared with the control simulation, weakening the temperature and vorticity anomalies and increasing strongly the vertical velocity anomalies associated to eddies.

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s_{1}^{τ} S S T'

) dominates the current‐induced effect (

s_{2}^{τ} \overset{true\to}{v_{s}^{o}}' . \frac{\overset{true\to}{τ_{s}}}{‖ \overset{true\to}{τ_{s}} ‖}

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Impacts of the Mesoscale Ocean‐Atmosphere Coupling on the Peru‐Chile Ocean Dynamics: The Current‐Induced Wind Stress Modulation

et al. 2018

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“…It consists in a fully compressible nonhydrostatic dynamical core with a runtime hydrostatic option on a C‐grid with terrain‐following mass vertical coordinate. A full suite of parameterization and physics schemes is included in WRF, enabling its use in a broad number of applications allowing for a good resolution of the horizontal scales of the atmospheric mesoscale features involved in Ekman‐driven upwelling systems (Boé et al, ; Bravo et al, ; Oerder et al, ; Renault et al, , ).…”

Section: Data Model Configurations and Methodologymentioning

confidence: 99%

Sensitivity of the Near‐Shore Oceanic Circulation Off Central Chile to Coastal Wind Profiles Characteristics

et al. 2019

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In Eastern Boundary Upwelling Systems (EBUS), the upwelling favorable wind speeds decrease toward the coast in the so‐called wind drop‐off coastal strip, which has been shown to be influential on the coastal upwelling dynamics, particularly in terms of the relative contributions of Ekman drift and Ekman suction to coastal upwelling. Currently, the wind drop‐off length scale is not properly resolved by the atmospheric forcing of regional ocean models in EBUS, featuring a smoother cross‐shore wind profile that results in stronger near‐shore speeds that could partly explain the coastal cold bias often found in those model simulations. Here, as a case study for the upwelling system off Central Chile, the sensitivity of upwelling dynamics to the coastal wind reduction is investigated using a Regional Ocean Modeling System (ROMS). Coastal wind profiles at different resolutions are first generated using a regional atmospheric model, validated from altimeter data, and then used to correct the coarse atmospheric wind forcing used for sensitivity experiments with ROMS. It is shown that the wind drop‐off correction induces a reduction in the oceanic coastal jet intensity, a stronger poleward undercurrent and a coherent offshore Ekman drift. It also yields a significant reduction of the cold bias along the coast compared to the simulation with “uncorrected” winds. Such reduction cannot be solely explained by the reduced Ekman transport only partially compensated by increase in Ekman suction. The analysis of the surface heat budget reveals in fact that an important contributor to the cooling reduction along the coast in the presence of coastal wind drop‐off is the heat flux term mediated by the reduction in the mixed‐layer depth. Overall, our results illustrate the nonlinear response of the upwelling dynamics to the coastal wind profiles in this region.

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Do submesoscale frontal processes ventilate the oxygen minimum zone off Peru?

Thomsen

Kanzow

Colas

et al. 2016

Geophysical Research Letters

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The Peruvian upwelling system encompasses the most intense and shallowest oxygen minimum zone (OMZ) in the ocean. This system shows pronounced submesoscale activity like filaments and fronts. We carried out glider‐based observations off Peru during austral summer 2013 to investigate whether submesoscale frontal processes ventilate the Peruvian OMZ. We present observational evidence for the subduction of highly oxygenated surface water in a submesoscale cold filament. The subduction event ventilates the oxycline but does not reach OMZ core waters. In a regional submesoscale‐permitting model we study the pathways of newly upwelled water. About 50% of upwelled virtual floats are subducted below the mixed layer within 5 days emphasizing a hitherto unrecognized importance of subduction for the ventilation of the Peruvian oxycline.

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Mesoscale SST–wind stress coupling in the Peru–Chile current system: Which mechanisms drive its seasonal variability?

Cited by 37 publications

References 83 publications

Impacts of the Mesoscale Ocean‐Atmosphere Coupling on the Peru‐Chile Ocean Dynamics: The Current‐Induced Wind Stress Modulation

Impacts of the Mesoscale Ocean‐Atmosphere Coupling on the Peru‐Chile Ocean Dynamics: The Current‐Induced Wind Stress Modulation

Sensitivity of the Near‐Shore Oceanic Circulation Off Central Chile to Coastal Wind Profiles Characteristics

Do submesoscale frontal processes ventilate the oxygen minimum zone off Peru?

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