Altimetry involving fine spatial scales: the Altimetry involving fine spatial scales: the GFDGFD lab the lab the subpolarsubpolar oceanocean

Peter Peter RhinesRhines11

Erik Erik LindahlLindahl11SirpaSirpa HäkkinenHäkkinen22

IakovIakov AfanasyevAfanasyev33

HjalmarHjalmar HatùnHatùn44

11UniversityUniversity of Washingtonof Washington22NASANASA GoddardGoddard

33MemorialMemorial University, St Johns NewfoundlandUniversity, St Johns Newfoundland44FaroeseFaroese Fisheries LaboratoryFisheries Laboratory

View from above: SSHfield in 1m diamter rotatingcylinder, configured as a polar-cap ocean and excitedby a buoyant source ofupper-ocean water at center

This talk introduces a laboratory analog of satellite altimeThis talk introduces a laboratory analog of satellite altimetry in work try in work funded by the funded by the VetlesenVetlesen Foundation of New York and NSFFoundation of New York and NSF--OCEOCE. Using the . Using the parabolic surface of a rotating fluid as a Newtonian reflecting parabolic surface of a rotating fluid as a Newtonian reflecting telescope we are telescope we are able to image the entire surface elevation field of a fluid circable to image the entire surface elevation field of a fluid circulation ulation experiment with accuracy better than 1 micron. This makes it poexperiment with accuracy better than 1 micron. This makes it possible to see ssible to see and quantitatively analyze dynamical features of model ocean cirand quantitatively analyze dynamical features of model ocean circulations that culations that were invisible previously. We argue that future widewere invisible previously. We argue that future wide--swath satellite altimetry, swath satellite altimetry, SWOTSWOT, should reveal not only more detail in features we know to be, should reveal not only more detail in features we know to be there there (boundary currents, fronts, convective structures, river plumes)(boundary currents, fronts, convective structures, river plumes) but can also but can also discover surface flow structures as yet unanticipated.discover surface flow structures as yet unanticipated.

WHY lab experiments?WHY lab experiments?

–– painless inclusion of many dynamical regimes (linear waves, nonlpainless inclusion of many dynamical regimes (linear waves, nonlinear inear eddies, fully turbulent, eddies, fully turbulent, geostrophicgeostrophic, , ageostrophicageostrophic, adiabatic, thermally , adiabatic, thermally active): active): texturetexture is not the same as spectral slopeis not the same as spectral slope

–– the opportunity to explore fluid physics absent or heavily paramthe opportunity to explore fluid physics absent or heavily parameterized eterized in numerical models: phase change, wave breaking, in numerical models: phase change, wave breaking, ageostrophicageostrophic deep deep convection, double diffusion, layering, boundary layers (top, boconvection, double diffusion, layering, boundary layers (top, bottom...[the ttom...[the ocean has no sidewalls]ocean has no sidewalls]

–– high resolution when in 3 dimensions …though only moderate Reynohigh resolution when in 3 dimensions …though only moderate Reynolds lds number (~10number (~1044) ) EkmanEkman number ~ 10number ~ 10--22

–– once you’ once you’ veve built it, you own it (easy to do long experimental runs…)built it, you own it (easy to do long experimental runs…)–– more surprises, aesthetics, and the observed fact that labs aremore surprises, aesthetics, and the observed fact that labs are social social

places.places.

(I) (I) Altimetry in the Altimetry in the GFDGFD lablab•• TaylorTaylor--ProudmanProudman: rotational stiffness: rotational stiffness•• topographic influence on topographic influence on SSHSSH: : barotropizationbarotropization of eddy fieldsof eddy fields•• interaction of topography with circulationinteraction of topography with circulation

form drag form drag ……. end of the . end of the baroclinicbaroclinic cascade: a major sink of cascade: a major sink of mesoscalemesoscale energy and momentumenergy and momentum

creation of jets and basin oscillationscreation of jets and basin oscillationsthe surface image of deep circulation, including the global the surface image of deep circulation, including the global MeridionalMeridional

OverturningOverturning•• RossbyRossby waves shaping gyrewaves shaping gyre--scale circulationsscale circulations

further further ββ--plane creation of jets and wakes with topographic ridges/risesplane creation of jets and wakes with topographic ridges/rises•• internal waves interacting with quasiinternal waves interacting with quasi--geostrophicgeostrophic flows:flows:

nearnear--inertial wave trapping in shear zonesinertial wave trapping in shear zonesinertial/internal waves (noninertial/internal waves (non--hydrostatic) wrapped round eddieshydrostatic) wrapped round eddies

•• deep convection: texture deep convection: texture •• combine altimetry with drifters, tracers, biocombine altimetry with drifters, tracers, bio--color, SST, subsurface color, SST, subsurface hydrographyhydrography•• nonnon--geostrophicgeostrophic interactions with interactions with mesoscalemesoscale fieldfield

baroclinicbaroclinic ββ--plume; plume; baroclinicbaroclinic instability, instability, radiation of near inertial waves from quasiradiation of near inertial waves from quasi--geostrophicgeostrophic flowsflowsvortex/gravity wave interaction in upper oceanvortex/gravity wave interaction in upper ocean

•• dynamics of thin, buoyant upper layers and boundary currentsdynamics of thin, buoyant upper layers and boundary currents

Cold diskCold disk

rapid rotation less rapid rotation

Forcing of a rotating bowl-shaped basin by a disk of surface cooling….the circulation is most intense far from the convective energy source. Boundary currents, gyres and deep convection develop from this compact source

Condie & Rhines ‘Topographic Hadley Cells JFM 1994

at high rotation (or large horizontal length scale) multiplejets form, guided by the topography of the basin

Evolution of balanced, Evolution of balanced, geostrophicgeostrophiceddies from 3eddies from 3--dimensional dimensional turbulenceturbulence

Initially 3Initially 3--dimensional turbulence converts to dimensional turbulence converts to tall, tall, geostrophicgeostrophic, cyclonic eddies., cyclonic eddies.

A 2mm glass cylinder is held vertically…at rest A 2mm glass cylinder is held vertically…at rest in the nonin the non--rotating frame…in a rotating rotating frame…in a rotating fluid… its 3D turbulent wake evolves into fluid… its 3D turbulent wake evolves into barotropicbarotropic cyclones cyclones

((CormacCormac Flynn, Univ.Flynn, Univ.of Washington of Washington GFDGFD lab)lab)

(numerical (numerical simssims: Smith & : Smith & WaleffeWaleffe PhysFlPhysFl 9999Morize,MoisyMorize,Moisy & & RibaudRibaud, , PhysFlPhysFl 05)05)

CarlCarl--Gustav Gustav RossbyRossby in the mid 1920s, with a large rotating platform for in the mid 1920s, with a large rotating platform for gfdgfdexperimentation: such an apparatus can experimentation: such an apparatus can ‘‘calculatecalculate’’ barotropicbarotropic polar polar ββ--plane plane circulations and fcirculations and f--plane plane baroclinicbaroclinic circulations with high resolution circulations with high resolution

NOAANOAA photo archivephoto archive

the laboratory polarthe laboratory polarββ--planeplane

(GFD lab, Univ. of Washington(GFD lab, Univ. of Washington):):

stiffness alongstiffness alongthe rotation axis: the rotation axis: 2D ribbons of2D ribbons oftracer tracer

The entire free-surface elevation field of a rotating fluid in the laboratory can be imaged and analyzed, by using it as a parabolic telescope mirror (Newton & Huygens 1672)

This ‘optical altimetry’ readily achieves a precision of better than 1 micron of surface elevation. The surface topography corresponds to the pressure field just beneath the surface. It is the stream-function for the geostrophic, hydrostatic circulation, which can be resolved to better than 0.1 mm sec-1.

Rhines, Lindahl & Mendez, J. Fluid Mech, 2007; Afanaseyev, Rhines & Lindahl, Physics of Fluids 2008 (accepted)

Experiments in fluids, 2008 (accepted)J. Atmos Sciences 2007

Rhines, J. Atmos Sciences 2007 Gharib & Dabiri, Exp. Fluids,2001, slope detector probe (FSGD)

robotically positionedlight source and camera

test fluid

Ω=2.2 sec-1 focal dist=1 m center of curvature = 2m

Simple set-up improved by a light camera knife-edge spherical correction mirror

2 m.

focus at z = g/2focus at z = g/2ΩΩ22~ 1 m for ~ 1 m for ΩΩ=2.2 s=2.2 s--11

For quantitative inversion of surfaceelevation, velocity, potential vorticitywe use colorometric mapping with a light source in the form of a squaremulti-hued panel: the imaged colorfield encodes the surface slope.

CIE (Commission Internationale d’Eclairage) L*a*b color space.

Inversion from surface elevation to velocity

accuracy of the method: simply change the rotation rate over a knownrange…altimetry accurate to 0.05% (std)

geostrophic

gradient

semi-geostrophic

….PV inversions

a high-wavenumber ‘test mountain’, a panelof ~ 1 cm squares beneath 15 cm of meanwater depth

the SSH image of the test mountain: an accurate Taylor-columntransmitted replica of the topography (left: slower flow; right: faster flow but both with small Rossby number.

Two ‘test mountains’ (red circles) with Two ‘test mountains’ (red circles) with azimuthalazimuthal flow forced over them yield flow forced over them yield a pattern of neara pattern of near--inertial waves and turbulent yet inertial waves and turbulent yet geostrophicgeostrophic eddieseddies

spherical-cap mountain

SeagliderSeaglider velocities between Iceland and velocities between Iceland and FaroesFaroes, showing strongly , showing strongly barotropicbarotropic velocity field (resolving tides): here we illustrate the velocity field (resolving tides): here we illustrate the

strong strong barotropicbarotropic component of the oceanic velocity field at high component of the oceanic velocity field at high latitude (the depthlatitude (the depth--average and surface velocities track closely).average and surface velocities track closely).

Long hydrostatic Kelvin waves, short inertial waves, shed cyclonLong hydrostatic Kelvin waves, short inertial waves, shed cyclonic eddies ic eddies generated by oscillatory body force with isolated mountain (oscigenerated by oscillatory body force with isolated mountain (oscillating the llating the

rotation rate of the table)rotation rate of the table)

Here we drive a uniform-angular-velocity zonal flow westward in the 1 m diameter polar β-plane. An isolated mountain generates lee-near-inertial waves which are ducted along the sharp shear line behind the mountain. A nearly stagnant Taylor column sits over the mountain. In this and other views the surface elevation (SSH) is seen as if illuminated from the side.

Particle trajectories (‘surface drifters’) superimposedupon the SSH field.

Lee Lee RossbyRossby--waves in the wake of a cylindrical mountain waves in the wake of a cylindrical mountain ((McCartney McCartney JFMJFM 19761976))

RossbyRossby waves are ‘onewaves are ‘one--way’: their way’: their phase propagation has a westward phase propagation has a westward component relative to the fluid: thus component relative to the fluid: thus they exist as lee waves for an they exist as lee waves for an eastward eastward flow but not a westward flow. Wave flow but not a westward flow. Wave drag peaks at: drag peaks at:

8.2 8.2 δδ//εε times the times the ‘‘naive estimatenaive estimate’’,,ρρfULfUL22δδHH

where where δδ==h/Hh/H is the fractional mountain height, is the fractional mountain height, εε the the RossbyRossby number, U the mean flow, L the radius and H number, U the mean flow, L the radius and H the total fluid depththe total fluid depth

note strong correlation of meridional velocityand topographic height…..wave drag

The same as the experiment above, yet with the meanflow reversed. A westerly (prograde, cyclonic) zonal flowencounters a small mountain (at 2 o’clock). Rossby wavedynamics produces standing waves downwind, a convoluted lee cyclone, intense jet structure wrapping round the mountain, and a ‘Lighthill block’ upstream. Thisstagnant blocking region is (in linear, yet finite topographytheory, a Rossby wave with vanishing intrinsic frequency and upstream group velocity for merid. wavenumbers < (β/U)1/2 .

Note the ruddy pressure features which are fine-scale evaporative convection cells, pillar-like cyclones. The edge of the block is outlined by convective rolls.

Here the controlling parameter βa2/U > 1meaning that the wake is stable; smaller values of this parameter yield unstable wake and transientRossby waves which ironically fill the hemisphere(they are not simple lee waves). See Polvani,Esler, Plumb JAS 1999 for a numerical studywith some of these features.

Streak image of the same experiment (dots 2 sec apart) showing iStreak image of the same experiment (dots 2 sec apart) showing intensityntensityof jets near mountain, lee of jets near mountain, lee RossbyRossby waves and upstream blockwaves and upstream block

A field of A field of tornadictornadic convection cells as seen in convection cells as seen in SSHSSH. Here the amplitude of the . Here the amplitude of the elevation features is ~ 10elevation features is ~ 10--66m (1 micron).m (1 micron).

Dye tracer view of the same convection cellsDye tracer view of the same convection cells

A key discovery using satellite altimetry is the A key discovery using satellite altimetry is the RossbyRossby wave/nonlinear eddy wave/nonlinear eddy structure of the upper km of the ocean (structure of the upper km of the ocean (CheltonChelton and collaborators). and collaborators). Almost Almost everywhere everywhere mesoscalemesoscale eddies drift westward, as largeeddies drift westward, as large--amplitude amplitude RossbyRossby waves waves similar in structure to the similar in structure to the baroclinicbaroclinic eddy describe in the MODE 1973 eddy describe in the MODE 1973 experiment in the western N Atlantic. The Antarctic Circumpolar experiment in the western N Atlantic. The Antarctic Circumpolar Current is Current is the main exception where eddies are systematically the main exception where eddies are systematically advectedadvected eastward.eastward.

And, many of these eddies carry fluid with westward with them, And, many of these eddies carry fluid with westward with them, in what in what amounts to a new form of general circulation. They have been tramounts to a new form of general circulation. They have been tracked with acked with RAFOSRAFOS floats and, tentatively, with their own potential floats and, tentatively, with their own potential vorticityvorticity signature.signature.

We have carried out a series of experiments to investigate We have carried out a series of experiments to investigate the mixed the mixed wave/eddy properties using wave/eddy properties using barotropicbarotropic and and baroclinicbaroclinic disturbances generated disturbances generated by a towed circular cylinderby a towed circular cylinder((AfanasyevAfanasyev, Rhines & , Rhines & LindahlLindahl 2008). 2008).

Dudley Chelton

Here the Here the colormetriccolormetric altimetry scheme altimetry scheme shows shows SSHSSH gradient as a perturbed gradient as a perturbed color field. The quantitative inversion color field. The quantitative inversion gives gives SSHSSH (right panels), velocity (right panels), velocity (arrows on left panels) and potential (arrows on left panels) and potential vorticityvorticity. (Every 1/100. (Every 1/100th th velocityvelocityvector is plotted).vector is plotted).

The flow is generated by towing a The flow is generated by towing a circular cylinder rapidly eastward circular cylinder rapidly eastward (upper panel), rapidly westward (middle (upper panel), rapidly westward (middle panel) or slowly panel) or slowly westardwestard (lower panel) (lower panel) about this polar about this polar ββ plane, generatingplane, generatingboth a vortex wake and both a vortex wake and RossbyRossby waveswaves

on a β plane cycloniceddies drift poleward(as in Dudley Chelton’sanalysis of altimetricSSH), while anti-cyclonesdrift equatorward.

This is seen here,with the vortices in the cylinder wake foreastward (left) andwestward (right) movingcylinders. The lower Hovmoeller

plot shows the wakepropagation speed forthe respective cases

calibrating the calibrating the altimetricaltimetric elevation and slope against known solid body rotation: elevation and slope against known solid body rotation: snapshot; std of slope = 2.0x10snapshot; std of slope = 2.0x10--4 4 corresponding to velocity of 0.5 x 10corresponding to velocity of 0.5 x 10--33 m secm sec--11

temporal smoothing readily increases the accuracy by at least a temporal smoothing readily increases the accuracy by at least a factor of 10. (The factor of 10. (The azimuthalazimuthal velocity at mid radius is 8 x 10velocity at mid radius is 8 x 10--3 3 m sm s--11.. ) high frequency surface waves

Independent surface velocity data come from Independent surface velocity data come from PIVPIV(particle imaging (particle imaging velocimetryvelocimetry))

PIV: 10 pixel AIV: 100 x

Buoyant source of fluid produces a ‘Buoyant source of fluid produces a ‘ββ--plume’ in a thin surface upperplume’ in a thin surface upper--ocean ocean surface layer, radiating west of the source and producing an unssurface layer, radiating west of the source and producing an unstable boundary table boundary

current. current. This is a video…sorry. This is a video…sorry.

The boundary current’s The boundary current’s baroclinicbaroclinic instability radiates nearinstability radiates near--inertial inertial waves (waves (AfanasyevAfanasyev, Rhines & , Rhines & LindahlLindahl, J , J AtmosAtmos SciSci 2007)2007)

radi

al co

ord

=>

zoom of the boundarycurrent reconstructedfrom altimetry. Thewave radiation site isshown.

time =>

SSH, surfacevelocity (every 100th

vector)

We combine alimetry with an optical thickness measurement of the upper layer of a stratified fluid, giving both barotropic andbaroclinic velocity fields, which is complete in the case of 2 layers.

a wedge-shaped cuvettewith uniformly dyed fluidcalibrates the optical layerthickness

SSH

thermal windvelocity

upper layerthicknessfield

surface andlower layervelocities

potentialvorticity

While this is a talk about a While this is a talk about a GFDGFD lab analogue of satellite altimetry, we want to lab analogue of satellite altimetry, we want to emphasize the pattern structure of the real ocean surface which,emphasize the pattern structure of the real ocean surface which, like the lab like the lab experiments, shows rich textures at fine scales when the approprexperiments, shows rich textures at fine scales when the appropriate imaging is iate imaging is available…for example in SST imagery, and here in available…for example in SST imagery, and here in SeaWiFSSeaWiFS ocean color.ocean color.

Our NASAOur NASA--funded research in the funded research in the subpolarsubpolar Atlantic has demonstrated the way Atlantic has demonstrated the way in which thin, finein which thin, fine--scale layers of lowscale layers of low--salinity water exert strong control over deep salinity water exert strong control over deep convection in the Labrador Sea. We first analyzed these through convection in the Labrador Sea. We first analyzed these through their their altimetricaltimetric SSHSSHfield, with deepfield, with deep--sea ground truth from our robotic sea ground truth from our robotic SeaglidersSeagliders. Then it became . Then it became apparent that these buoyant surface layers determine the shape aapparent that these buoyant surface layers determine the shape and intensity of the nd intensity of the dominant spring phytoplankton bloom in the western dominant spring phytoplankton bloom in the western subpolarsubpolar Atlantic. (see Atlantic. (see HatunHatun et et al., J. Phys. al., J. Phys. OceanogrOceanogr. 2007, Williams, Rhines & . 2007, Williams, Rhines & EriksenEriksen, , J.G.RJ.G.R. submitted 2008). . submitted 2008).

SeaWiFS satellite: oceanic surface phytoplankton2005 days 91-120

a plume of buoyant, low salinitywater flows southwestward fromthe coast of Greenland, as partof the cyclonic subpolar gyre.

Labrador Sea: altimetry, SST, ocean color, Seaglider subsurface hydrography and bio-optics

Eleanor Williams, UW

missing here: video of satellite missing here: video of satellite altimeteryaltimetery showing coherent eddies crossing the showing coherent eddies crossing the Labrador Sea, which reinforce their importance in controlling deLabrador Sea, which reinforce their importance in controlling deep convection ep convection

and biological productivity.and biological productivity.

AVHRR satellite SST image with Seaglidertrack superimposed. This mission provided thesubsurface structure of the eddies and mean offshore circulation as wellas the vertical structure ofthe phytoplankton bloom

(Hatun, Eriksen & Rhines JPO 2007,Williams, Rhines & Eriksen 2008)

T em

pera

ture

(deg

C)

March 23, 2amMarch 24 2005, 10pmaltimetry pass

V ~ 0.5 m/sV ~ 0.35 m/s

Velocities from altimetrySS

H (m

m)

Dep

th (m

)

North

EastAltimetry showing strong anticyclonic eddy spinning off the Greenland coastal current, withSeaglider deep thermal structure, along its path round the eddy.

SeagliderSeaglider based cross sections of the based cross sections of the anticyclonicanticyclonic eddy (for radius 0 to 40 km) eddy (for radius 0 to 40 km) shown in the previous slide. The cold, low salinity water in theshown in the previous slide. The cold, low salinity water in the top 100m top 100m provides a buoyancy barrier for deep convection and a stable envprovides a buoyancy barrier for deep convection and a stable environment for ironment for phytoplankton growthphytoplankton growth

AzimuthalAzimuthal velocity cross section of the eddy, showing deep penetration ofvelocity cross section of the eddy, showing deep penetration of strong strong currents (> 1 knot) to 1000m. The surface velocity matches the currents (> 1 knot) to 1000m. The surface velocity matches the altimetricaltimetric velocity well.velocity well.This is encouraging, since the velocity core extends only 25 km This is encouraging, since the velocity core extends only 25 km from the center at the surface.from the center at the surface.

subsurface, small-scale detail (here, of temperature) is traced out by high resolution (~ 3 km)Seaglider sections to 1000m depth

cold Arctic water flowing south through Davis Straitwarmer Irminger Sea water circulating in subpolar gyre

mixed layer deepening southward and as winterarrives

The important global mapping of The important global mapping of RossbyRossby waves and their nonlinear waves and their nonlinear RossbyRossby--eddy eddy cousins by cousins by CheltonChelton and collaborators motivates us to follow in more detail and collaborators motivates us to follow in more detail RossbyRossbywave dynamics in the wave dynamics in the GFDGFD lab.lab.

RossbyRossby wave mode (5,1) on wave mode (5,1) on barotropicbarotropic, polar , polar ββ--plane (North Pole at center), excited at frequency 0.11f by plane (North Pole at center), excited at frequency 0.11f by plunger at lower left. plunger at lower left. ΩΩ=3.5 s=3.5 s--11

Longuet-Higgins, PRSA 64

2 ( , ) i tx x y e

tωψ βψ δ −∂

∇ + =∂RossbyRossby wave Green’s function for an oscillatory point source wave Green’s function for an oscillatory point source

ψψ=exp(=exp(--iiββx/2x/2ωω--iiωωtt) ) HH00(2)(2)((ββr/2r/2ωω))

viewed from southwest of the ‘tweak’.viewed from southwest of the ‘tweak’.Parabolic wave crests sweep westwardParabolic wave crests sweep westward

2 ( , ) i tx x y e

tωψ βψ δ −∂

∇ + =∂

xx

y

Polar Polar ββ--plane, oscillating plane, oscillating RossbyRossby wave source, no initial wave source, no initial mean zonal flow mean zonal flow (video)(video)

The PV elasticity…the restoring effect for Rossby waves…is very scale-dependent

Altimetric SSH field, oscillatory Rossby wave source, polar β-plane

long Rossby waves propagate westward and poleward from their source

short Rossbywaves appeareast of theforcing region

sorry…more videos

In the lab we stress the immense influence of seafloor topographIn the lab we stress the immense influence of seafloor topography on the circulation. In y on the circulation. In the the subpolarsubpolar Atlantic altimetry has been combined with Atlantic altimetry has been combined with in situin situ drifting drifting RAFOSRAFOS floats to floats to pinpoint the dynamics of the North Atlantic Current as it is guipinpoint the dynamics of the North Atlantic Current as it is guided through topographic ded through topographic

fracture zones. (fracture zones. (Bower & Van Bower & Van AppenAppen, , JPOJPO 2008)2008)

North Atlantic Current: a shallow North Atlantic Current: a shallow upper ocean current yet its path is upper ocean current yet its path is controlled by deep fracture zones:controlled by deep fracture zones:

altimetry verified by floatsaltimetry verified by floats

Bower & van Appen JPO 2008

Topographic control over circulation, waves and Topographic control over circulation, waves and mesoscalemesoscale eddies: eddies: a bowla bowl--shaped basin divided by radial ridges into 4 basinsshaped basin divided by radial ridges into 4 basins

yet another video that you can’t see!yet another video that you can’t see!

Iceland

Faroes

Iceland

Faroes

600

840

420-480

SubpolarSubpolar ocean climate is 3ocean climate is 3--dimensional, dimensional, with intense topographic controlwith intense topographic control

(I) (I) Altimetry in the Altimetry in the GFDGFD lablab•• TaylorTaylor--ProudmanProudman: rotational stiffness: rotational stiffness•• topographic influence on topographic influence on SSHSSH: : barotropizationbarotropization of eddy fieldsof eddy fields•• interaction of topography with circulationinteraction of topography with circulation

form drag form drag ……. end of the . end of the baroclinicbaroclinic cascade: a major sink of cascade: a major sink of mesoscalemesoscale energy and momentumenergy and momentumcreation of jets and basin oscillationscreation of jets and basin oscillationsThe surface image of deep circulation, including the global The surface image of deep circulation, including the global MeridionalMeridional OverturningOverturning

•• RossbyRossby waves shaping gyrewaves shaping gyre--scale circulationsscale circulationsfurther further ββ--plane creation of jets and wakes with topographic ridges/risesplane creation of jets and wakes with topographic ridges/rises

•• internal waves interacting with quasiinternal waves interacting with quasi--geostrophicgeostrophic flows:flows:nearnear--inertial wave trapping in shear zonesinertial wave trapping in shear zonesinertial/internal waves (noninertial/internal waves (non--hydrostatic) wrapped round eddieshydrostatic) wrapped round eddies

•• deep convection: texture deep convection: texture •• combine altimetry with drifters, tracers, biocombine altimetry with drifters, tracers, bio--color, SST, subsurface color, SST, subsurface hydrographyhydrography•• nonnon--geostrophicgeostrophic interactions with interactions with mesoscalemesoscale fieldfield

baroclinicbaroclinic ββ--plume; plume; baroclinicbaroclinic instability, instability, radiation of near inertial waves from quasiradiation of near inertial waves from quasi--geostrophicgeostrophic flowsflowsvortex/gravity wave interaction in upper oceanvortex/gravity wave interaction in upper ocean

•• dynamics of thin, buoyant upper layers and boundarydynamics of thin, buoyant upper layers and boundary currentscurrents

The The GFDGFD lab analog suggests the value lab analog suggests the value to be found with a to be found with a future widefuture wide--swath altimeter: high swath altimeter: high resolution reveals features invisible resolution reveals features invisible with present technology. Boundary with present technology. Boundary currents, deep convection sites, currents, deep convection sites, intricate topographically controlled intricate topographically controlled circulation, midcirculation, mid--ocean jets, ecologically ocean jets, ecologically important fronts should all be visible important fronts should all be visible with this new capability.with this new capability.

HakkinenHakkinen and Rhines are using satellite and Rhines are using satellite altimetry, seaaltimetry, sea--surface drifters, deep surface drifters, deep SeaglidersSeagliders and models to reconstruct and models to reconstruct the the meridionalmeridional circulation of the circulation of the northern Atlantic. Many of the northern Atlantic. Many of the elements described in the previous elements described in the previous slide from our slide from our GFDGFD lab analogue are lab analogue are present in nature.present in nature.

For papers and more lab images (including For papers and more lab images (including videos) visitvideos) visitwww.ocean.washington.edu/research/gfdwww.ocean.washington.edu/research/gfd

Thanks to NASA Ocean Surface Topography Science Team Thanks to NASA Ocean Surface Topography Science Team funding we have been able to pursue the funding we have been able to pursue the real thing: real thing: altimetricallyaltimetricallyobserved ocean circulation and climate change.observed ocean circulation and climate change.