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Moisture flux during high and low NAO: : concentration in the high-latitudestorm tracks of the ~ 2 petawatts of latent heat flux … whichis ~0.7 Sverdrup (0.7 megatonnes/sec) of freshwater flux1993 JFM 1000mb moisture flux1993 velocity 1000mb 1996 JFM

Greenland as barrier and stirring rod:Integrated pressure drag (east-west) on Greenland’s slopes (negative=eastward force on solid Earth)dashed: NAO index winter 2004Jung & Rhines JAS in press 2007

1000 HPa height correlated with strong westerly pressure dragon Greenlands slopes (1958-2001, lags -6, 6,-4, 4,-2, 0,+4 days, 2-102day high-pass filtered)0 days lag

50 HPa dynamic height: stratospheric polar vortex displaced / deformedtoward Greenland during high-drag events…hemispheric-scale scale responseStratosphere correlatesover hemispheric scale,with earlier precursor

Shapiro et al AMS abs 02Doyle & Shapiro Tellus 99SSMI windspeed in tip-jet

Greenland’s ‘gap jet’: downslope wind, upward propagating gravity wavesreach stratosphere (ECMWF(model Jung & Rhines JAS in press 2007)Three resolutions:T95 T255T799210 km grid 25 km grid

T511L60 ECMWF analysis25 Dec 2004 0Z – 27 Dec 12 ZSLP and Θ on PV=2000surfacelife cycle of cyclones/jet streamencounters with Greenland:tip-jet, gap jet, expansion oflee cyclone to ~ 2000 kmsize of Greenland.

48 hour back trajectories (H.Wernli(code)color = vorticitycolor=heightgap jettip-jet25 Dec 2004 17 Jan 2005

Jet-like circulations, Rossby wake created by broadwesterly flow past a small mountain (polar β-planecentered on North Pole, barotropic mode)GFD lab Univ of Washington Rhines et al. J.Fluid Meck 2007, JAS 2007 in press

2. Through the sea surface

NCEP windstressQuikSCAT windstress12 Jan 2001Dudley Chelton (pers communication)

COAMPS tip-jet air/sea heat flux (Feb 97) andclimatological oceanic PV (potential vorticity) ) at1000m depthPickart, Spall, Ribbegard, Moore & Milliff Nature 2002; Hay & Moore this meeting

The global context:net air/sea heat flux(NOC 1.1a annual mean)SH+LH+LW+SW= convergence ofheat by ocean circulationwarming of atmosphereby oceanSH+LH+LW= local, seasonally storedheating + heat imported byocean circulation, annualmean…upward ~ everywherenote SW == local,seasonal heat storageSH = sensible heat fluxLH = latent heat fluxLW = net long wave radSW = net short wave rad

fraction of annual-mean oceanic warming of atmosphere dueto lateral heat flux by ocean circulationRhines & Häkkinen, 2002, 2008 ASOF volume-sign means F oceandownward yet F atmoupward

3. Gyre dynamics

subpolar gyre determined by RAFOS floatsfloats Bower et al, Nature2003 σ 0 = 27.5 (~ 1000 m in south) 1993-2001 mostly isopycnal :determining the meridional pathways of the gyre

ALTIMETRIC SSH AND GEOSTROPHIC VELOCITYFIELD EOF1s(update using only TOPEX/Poseidon and Jason-1 data, time period covered: October 1992 to March 2005; altimetric data willundergo further refinement: new GRACE based orbits etc)To get SSH /VELOCITY in anyindividual point one needs to multiplythe value of the spatial pattern (left)by the time series value on the right)SSH HAS UNITS OF CMVELOCITIES ARE NORMALIZEDSO THEY ARE DIMENSIOLESSSeasatGeosatERS-1/2,TOPEX/Poseidon Jason-1

Yashayaev, 2006altimetricheightand stericheight:a 2-modedescriptionof thecirculation1960s dynamicheightmaximumequal to today’s....GSA….

altimetric height (AH)sea surface trend, 1992-20062006global warming signal + gyre scale dynamics

eof-1 1 of N Pacific AH (‘breathing mode’) in whichsubpolar gyre varies in phase with subtropical gyreand Kuroshio extension velocity (NPC(NPC)Cummins & Freeland 2007 PiOreproducible with simplewind-driven GCM

figure from D. Roemmich (NASA OSTST, Hobart, 2007);Willis, Roemmich & Cornuelle, 2002 JGRAltimetric surfaceheight trendSteric surfaceheight trend

4. ocean gyres and MOC

accompanying surface SP gyre deceleration is the opening of the easternAtlantic meridional pathway to stronger advection of subtropical waters byNAC extension ( (HatunHatun et al. 2005).This shift can also be seen with surface drifters….

earlymiddle‘departure’Lagrangianmeanflow: driftersreleased in asubtropical GulfStream box (red,blue)red: speed> 30cm/seccyan: driftersarriving at boxlateHäkkinen & RhinesScience submitted 2007

“Surface drifters deployed in the subtropical and subpolarNorth Atlantic from 1990 to 2002 show almost noconnection between the subtropical and subpolar gyres;only one drifter crosses the intergyre boundary eventhough other data types (e.g., dynamic topography andtracers) suggest a major connection).”Brambilla & Talley 2006 JGR)

‘arrival’ Lagrangianmeanflow: driftersarriving at a boxcentered on Rockallplateau (green)and departing fromit (blue)also seen byaltimetry…

Wind-stresscurl for thethree periods

• Salinization/warming of the high latitudes thus involves gyreexchange dynamics, local and global wind- and buoyancyforcing…a rich story of interaction.In the western SP gyre with storm track/tip jet forcing, anopposing tendency of low-salinity water advection, with itsstabilizing effect on the water column is evident.

potential temperature along glider tracks:-Arctic waters from Baffin Bay;-warmIrminger Sea water from boundarycurrent along w. Greenland-thin, cold, low-salinity surface layer advectedover-top of Labrador Sea from Greenland coast

advection of low salinity surface layer off the westGreenland coast shapes both deep convection region,Labrador Sea Water production and primary springplankton bloom ( (Hatun, Eriksen & Rhines 2007 JPO)black contours:Lavender ARGOstreamfunctiongrey shades: altimetricEKEcolors: depth of winterconvection in 1968.from Pickart et al. 2002)

Labrador Sea boundary current at the 2800m isobath on the Labradorcontinental slope: Denmark Strait Overflow Water is the largest velocityyet all the water masses feeding the global MOC are riding on a strongbarotropic (depth-independent) flow, and this flow can signal efficientlyalong the continental-slope PV waveguideCuny & Rhines, DSR 2005

mooring area and ARGO float determined Labrador Seaboundary current 53-54N, 54N, 48-52WFischer, Schott & Dengler 2003 JPO

exchanges across the Iceland-FaroesFaroes-Shetland Ridgeand Channels…estimates ofIceland420-480FaroesFaroes840600

Hansen & Osterhus PiO 2000

Water-mass transformation on Θ/S plane:Faroe-Bank Channel Mauritzen et al. 2005 DSR: mixingdownstream of the final sill dilutes the dense cold water, withimpact on the global MOC

Temperature section following glider 101 (Nov 2006-March 2007)Wyville-Thompson Basinmultiple crossings of Faroe-Bank ChannelIceland-Faroe Ridge

Seaglider 101 9 June-30 Aug 2008: temperature sectionon south slope of Iceland-FaroeRidge (plus north-south section at end…likePoseidon section of Meincke, , 1976). Thin, cold bottom layer0357Zencountered widely31 Aug 07Patrolling east-west along southern flank of Iceland-Faroe RidgeIceland-Faroe Ridgesouth north

South NorthIceland Faroe Ridge ‘Poseidon’1977 Section (Meincke 1978)

close to the Poseidon section on theprevious slide, this weeks’ Seaglidersection…blue-light light particlebackscatter showing biologicalactivity and potential density, salinity,IFR, SG101 Aug 2007

fluorescence and oxygen saturation

Seeking the cold, thin overflows on the Iceland-Faroe Ridge.

T and S over the Iceland-Faroeridgesouth → north

These figures show that (1) tides are resolved well enough to show the backgrounddepth-averaged velocity (lower left) and (2) that the surface current (crudelyestimated from a 5 to 10 minute surface drift each dive) is quite e close to the depthaveraged current, implying a strong barotropic mode for the horizontal current.

Conclusions: These are examples of flows in which vertical Coriolis stiffness andpotential vorticity gradients lead to tall structures, vertical propagation and rapidhorizontal propagation; ; hence, in the ocean, interaction of gyres and overturningcirculations.From the stratosphere to the deep ocean we find tall flow-structures (jets, waves, eddiesembedded in gyres), yet sub-synoptic synoptic scale ‘detail’ ’ turns out to be crucial, and sites ofconcentrated flow, heat/freshwater flux, momentum flux can radiate outward toinfluence gyres and global overturning. Satellite remote sensing of altimetric seasurface height, scatterometer winds, SST (including through-cloud radiometers), oceancolor illustrate the wide spectrum of length scales involved in the general circulation.Altimetry and ARGO/ship/glider hydrography provides fields of both barotropic andbaroclinic geostrophic velocity.-tip jets, gap jets in the winds round Greenland and their effect on air/seaheat/fwfw/momentum fluxes-advectedlow salinity layers in the northwest Atlantic-underlyingbarotropic ocean circulation of subpolar gyres; Atlantic and globaltrends with accelerating subtropical gyres, decelerating surfacesubpolar Atlantic gyre-fine-scale gyre interaction with Atlantic inflow to Nordic Seas-Iceland-FaroeRidge, Faroe-Bank Channel sources of deep MOC branch: fine-scalemixing and overflow pathwaysThis enormous range of length-scale in the dynamics requires special observations.Satellite altimetry + ARGO, ship XBT/ADCP, hydrography are giving usa near-global non-eddy resolving synoptic observation systemIn addition, focused fine-scale observations are keys to these scale-jumpinginteractions.