Modification of the Gulf Stream through Strong Air–Sea Interactions in Winter: Observations and Numerical Simulations

Xue, Huijie; Bane, John M.; Goodman, L.

doi:10.1175/1520-0485(1995)025<0533:motgst>2.0.co;2

Cited by 39 publications

(66 citation statements)

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“…Processes that determine SST in WBCs include surface heat fluxes (Cayan 1992), Ekman transport acting on the strong SST fronts (Xue et al 1995), eddies (Qiu 2000), and seasonal variability of upper-ocean mixing leading to the reemergence of SSTAs (Alexander and Deser 1995). Westwardpropagating Rossby waves driven by basin-scale wind stress curl ($ 3 t) anomalies can initiate changes in ocean circulation in WBCs that lead to meridional displacement of the front (Nakamura and Kazmin 2003) and geostrophic advection changes .…”

Section: Introductionmentioning

confidence: 99%

Role of the Gulf Stream and Kuroshio–Oyashio Systems in Large-Scale Atmosphere–Ocean Interaction: A Review

Alexander²,

et al. 2010

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Ocean-atmosphere interaction over the Northern Hemisphere western boundary current (WBC) regions (i.e., the Gulf Stream, Kuroshio, Oyashio, and their extensions) is reviewed with an emphasis on their role in basin-scale climate variability. SST anomalies exhibit considerable variance on interannual to decadal time scales in these regions. Low-frequency SST variability is primarily driven by basin-scale wind stress curl variability via the oceanic Rossby wave adjustment of the gyre-scale circulation that modulates the latitude and strength of the WBC-related oceanic fronts. Rectification of the variability by mesoscale eddies, reemergence of the anomalies from the preceding winter, and tropical remote forcing also play important roles in driving and maintaining the low-frequency variability in these regions. In the Gulf Stream region, interaction with the deep western boundary current also likely influences the low-frequency variability. Surface heat fluxes damp the low-frequency SST anomalies over the WBC regions; thus, heat fluxes originate with heat anomalies in the ocean and have the potential to drive the overlying atmospheric circulation. While recent observational studies demonstrate a local atmospheric boundary layer response to WBC changes, the latter's influence on the large-scale atmospheric circulation is still unclear. Nevertheless, heat and moisture fluxes from the WBCs into the atmosphere influence the mean state of the atmospheric circulation, including anchoring the latitude of the storm tracks to the WBCs. Furthermore, many climate models suggest that the large-scale atmospheric response to SST anomalies driven by ocean dynamics in WBC regions can be important in generating decadal climate variability. As a step toward bridging climate model results and observations, the degree of realism of the WBC in current climate model simulations is assessed. Finally, outstanding issues concerning oceanatmosphere interaction in WBC regions and its impact on climate variability are discussed.

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Section: Introductionmentioning

confidence: 99%

Role of the Gulf Stream and Kuroshio–Oyashio Systems in Large-Scale Atmosphere–Ocean Interaction: A Review

Alexander²,

et al. 2010

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“…However, Xue et al (1994) examined moored observations of the response of the Gulf Stream to the passage of a wintertime storm characterized by strong cooling and concluded that changes in heat storage are dominated by the surface heat flux. This study focuses on observations from drifting profiling instruments, which are quasi-Lagrangian, and consequently reduce, but as we will see, don't eliminate the effects of horizontal advection.…”

Section: Discussionmentioning

confidence: 99%

“…However, Eulerian observations of upper ocean heat content changes during a wintertime storm passage over the Gulf Stream off the coast of South Carolina demonstrate that the heat budget is dominated by the strong buoyancy forcing associated with the storm (Xue et al, 1994). Xue et al (1994) suggest that the discrepancies between their results and the results of Kelly and Qui (1995);Dong and Kelly (2004) are related to the fact that after the Gulf Stream has separated from the coast, and is flowing east-west (as in Kelly and Qui (1995) …”

Section: Advective Effectsmentioning

confidence: 99%

Near-inertial and thermal upper ocean response to atmospheric forcing in the North Atlantic Ocean

Silverthorne¹

2010

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Observational and modeling techniques are employed to investigate the thermal and inertial upper ocean response to wind and buoyancy forcing in the North Atlantic Ocean. First, the seasonal kinetic energy variability of near-inertial motions observed with a moored profiler is described. Observed wintertime enhancement and surface intensification of near-inertial kinetic energy support previous work suggesting that near-inertial motions are predominantly driven by surface forcing. The wind energy input into surface ocean near-inertial motions is estimated using the Price-WellerPinkel (PWP) one-dimensional mixed layer model. A localized depth-integrated model consisting of a wind forcing term and a dissipation parameterization is developed and shown to have skill capturing the seasonal cycle and order of magnitude of the near-inertial kinetic energy. Focusing in on wintertime storm passage, velocity and density records from drifting profiling floats (EM-APEX) and a meteorological spar buoy/tethered profiler system (ASIS/FILIS) deployed in the Gulf Stream in February 2007 as part of the CLIvar MOde water Dynamics Experiment (CLIMODE) were analyzed. Despite large surface heat loss during cold air outbreaks and the drifting nature of the instruments, changes in the upper ocean heat content were found in a mixed layer heat balance to be controlled primarily by the relative advection of temperature associated with the strong vertical shear of the Gulf Stream. Velocity records from the Gulf Stream exhibited energetic near-inertial oscillations with frequency that was shifted below the local resting inertial frequency. This depression of frequency was linked to the presence of the negative vorticity of the background horizontal current shear, implying the potential for near-inertial wave trapping in the Gulf Stream region through the mechanism described by Kunze and Sanford (1984). Three-dimensional PWP model simulations show evidence of near-inertial wave trapping in the Gulf Stream jet, and are used to quantify the resulting mixing and the effect on the stratification in the Eighteen Degree Water formation region.

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“…Sun and Hsu (1988), using a twodimensional planetary boundary layer model for the East China Sea, found good agreement with AMTEX observations and sensible and latent heat fluxes of 300 and 700 Wm −2 , respectively, which are close to the observed values. Xue et al (1995Xue et al ( , 2000 used a two-dimensional numerical coupled atmosphere-ocean model for cold-air outbreaks and found maximum heat fluxes of 1,500 and 1,300 Wm −2 , respectively. Modeling of cold-air outbreaks using a full three-dimensional coupled atmosphere-ocean model was done for the Gulf Stream for a 48-h cold-air outbreak in January 1998 over the Gulf Stream (Li et al 2002).…”

Section: Cold-air Outbreaksmentioning

confidence: 99%

“…The impact of the cold/warm water front on the atmosphere over the Kuroshio and Gulf Stream regions has been well-documented to include low-level moisture convergence, deepening of the planetary boundary layer, and generation of storms (e.g., Sun and Hsu 1988;Xue et al 1995Xue et al , 2000. Recent discussions are given by , Small et al (2008), Taguchi et al (2009), andTokinaga et al (2009).…”

Section: The Kuroshio Extension System Region and North Pacific Subtrmentioning

confidence: 99%

Turbulent heat fluxes during an intense cold-air outbreak over the Kuroshio Extension Region: results from a high-resolution coupled atmosphere–ocean model

et al. 2011

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The coupled ocean atmosphere mesoscale prediction system that includes the Navy Coastal Ocean Model has been configured for the Kuroshio Extension region using multiple one-way nested high-resolution grids. The coupled model system was used to simulate a strong cold-air outbreak event from 31 Jan to 7 Feb 2005 in good agreement with meteorological data from a surface buoy data and QuikSCAT scatterometer winds. Latent heat fluxes and sensible heat fluxes were computed during the event with daily averages in excess of 1,500 W/m 2 and 500 W/m 2 , respectively, and combined instantaneous turbulent heat fluxes up to 2,300 W/ m 2 . The largest heat fluxes were found in two large meanders of the Kuroshio and along its southern flank. Strong gradients in turbulent heat fluxes coincided with strong sea surface temperature gradients and were maintained during the cold-air outbreak simulation. The large turbulent heat fluxes lead to significant subtropical mode water formation during the event at a rate about 10 Sv in the cyclonic recirculation region south of the Kuroshio. This increased the volume of core layer mode water within the temperature range 16°C to 18°C by 10% and increased the surface area of that layer directly exposed to the atmosphere by a factor close to 5 in the model domain.

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Modification of the Gulf Stream through Strong Air–Sea Interactions in Winter: Observations and Numerical Simulations

Cited by 39 publications

References 0 publications

Role of the Gulf Stream and Kuroshio–Oyashio Systems in Large-Scale Atmosphere–Ocean Interaction: A Review

Role of the Gulf Stream and Kuroshio–Oyashio Systems in Large-Scale Atmosphere–Ocean Interaction: A Review

Near-inertial and thermal upper ocean response to atmospheric forcing in the North Atlantic Ocean

Turbulent heat fluxes during an intense cold-air outbreak over the Kuroshio Extension Region: results from a high-resolution coupled atmosphere–ocean model

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