young-oh kwon et al
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Role of the Gulf Stream and Kuroshio-Oyashio Systems in Large-Scale Atmosphere-Ocean Interaction: A Review. Young-oh Kwon et al. Outline. Intorduction Processes affecting the SST variability in the WBCs WBCs and the basin-scale climate variability - PowerPoint PPT PresentationTRANSCRIPT
Role of the Gulf Stream and Kuroshio-Oyashio Systems in Large-
Scale Atmosphere-Ocean Interaction: A Review
Young-oh Kwon et al.
Outline
• Intorduction• Processes affecting the SST variability in the
WBCs• WBCs and the basin-scale climate variability• Performance of climate models on simulation
of WBC variability• Outstanding issue
Introduction
• There are “exceptionally” strong atmosphere-ocean interaction over West Boundary Current region.– Mean and Variances(SSTA)– Interannual and longer time scale– Heat transport
• Atmosphere response to WBC STTAs with several issues
Processes affecting the SST in WBC region
Interesting issues
• The Connection between frontal-scale boundary layer ocean-atmosphere interaction and the basin-scale variability.
• Potential changes in WBC ocean duce to global warming.
• The relationship between the Meridional overturning circulation and Gulf Stream in North Atlantic.
• Interbasin connection between the KOE and GS variability.
Processes affecting the SST variability in the WBCs
• Shift of oceanic fronts• Oceanic advection• Surface heat fluxes• Ekman transport• Reemergence mechanism• Remote wind stress curl forcing
communicated via oceanic Rossby wave• Tropical atmosphere teleconnections
Shift of oceanic front
• Decadal SST variability is particularly strong along the SubArctic Frontal Zones.
Oceanic advection
• In the WBCs on interannual and longer time scales is determined mainly by anomalous geostrophic advection, which tends to dominate over Ekman advection and Qnet.
Surface heat flux
• Qnet in the WBC
Ekman Transport
• Ekman transport responds quickly to changes in surface wind and can generate SSTA.
• To reinforce the Qnet in mid-latitudes because stronger westerlies cool the ocean by the sensible and latent heat fluxes and by southward Ekman transport.
• The cross-frontal cold Ekman advection lowers the near-surface stratification on the warmer side of the front and enhance vertical mixing.
Reemergence mechanism
Remote wind stress curl forcing communicated via oceanic Rossby
wave
Tropical Teleconnection
WBCs and the basin-scale climate variability
• Decadal SST variability in the WBCs• Oceanic dynamics and decadal variability• Surface heat flux damping and implications• Decadal variability in atmosphere-ocean
coupled general circulation models
Decadal SST variability in the WBCs
Oceanic dynamics and decadal variability
• As the Rossby waves propagate westward, they integrate the stochastic forcing to increase the variance and dominant period of dynamic ocean properties until reaching a maximum near the WBC.
• The spatial resonance mechanisms could generate a decadal peak in the ocean by stochastic atmosphere.
Surface heat flux damping and implications
Decadal variability in atmosphere-ocean coupled general circulation
models• Coupled climate models generally indicate
that ocean-atmosphere interaction in WBC regions is a key factor in generating extropical decadal variability.
• Although earlier studies suggested that North Atlantic decadal variability in SST was primarily reflecting a passive response to the atmospheric forcing.
Performance of climate models on simulation of WBC variability
• High-resolution ocean simulations• Simulation of the Kuroshio and Gulf Stream at
non-eddy-permitting resolution• Atmospheric simulations
High-resolution ocean simulations
• For KOE:– KE’s path variability can be tied largely to wind
forcing.
• For GS:– Interaction between DWBC.
Simulation of the Kuroshio and Gulf Stream at non-eddy-permitting
resolution
Outstanding issues
• How are the frontal-scale and basin-scale atmosphere-ocean interactions related?
• What is the large scale atmospheric circulation/wind stress curl response to the WBC SSTA
• Global warming and the WBCs• Relation between the Gulf Stream and the
MOC• Connection between GS and KOE variability