How to form halocline water?Halocline formationRetreat of the Cold Halocline (Steele and Boyd, 1998)Retreat of the Cold Halocline (Steele and Boyd, 1998)Decadal averages of Russian Data 1950s to 1980s“Levitus” for the ArcticThe (partial) return of the Cold Halocline (Boyd et al, 2002)Western versus Eastern Arctic HaloclineShift of Pacific/Atlantic FrontBering Strait and the Chukchi SeaGeneric Pacific Water circulation Chukchi Sea OutflowChukchi slope velocity 2002-2003 red=73 20N blue=73 37NChukchi Slope 2002-2003 TS-propertiesDense Water Outflow – e.g. from coastal polynyas (e.g. Martin et al, 2004)Wind effectsResults of a strong westward windUpwelling versus polynyas??Can we get this TS from Bering Strait??Influence of shelf waters??Do the volumes work out?The Eddy Band-wagonEddies in the Beaufort Sea e.g.,Hunkins and Manley, Plueddemann and MANY others http://www.whoi.edu/science/PO/arcticgroup/proEddies in the non-Beaufort ArcticUpper Arctic Ocean Circulation and VentilationHow to form halocline water?Adapted from Steele and Boyd, 1998Atlantic waterSurface Water- cannot form Halocline water simply by mixing(Aagaard, 1981)Temp Fresh SaltyADD COLD, SALTYAagaard et al, 1981Rudels et al, 1996Temp SaltyConvectADD COLD, FRESH~ 50m~ 100m~ 50m~ 100mADVECTIVE HCCONVECTIVE HCSteele and Boyd, 1998 – source of halocline water differs (advective or convective)Woodgate et al, 2001 – temperature of halocline water differs(convective must be at freezing temperature, advective may or may not be at freezing)Halocline formationWoodgate etal, 2001Retreat of the Cold Halocline (Steele and Boyd, 1998)In 1995, only Makarovhas a cold haloclineUse salinity in 40-60m band as an indicatorRetreat of the Cold Halocline (Steele and Boyd, 1998)Injection point of freshwater (Russian Rivers) has changedBacked up by chemical data,Ekwurzel et al., 2001PREVIOUS – RW into Eurasian Basin – CHL in Eurasian Basin1995 – RW along shelf instead – no CHL in Eurasian BasinDecadal averages of Russian Data 1950s to 1980shttp://nsidc.org/data/g01961.html(see also Swift et al, 2005 annual averages in boxes 1948-1993 - ftp:://odf.ucsd.edu/pub/jswift/arctic_aari_method_B“Levitus” for the Arctichttp://psc.apl,washington.edu/Climatology.htmlThe (partial) return of the Cold Halocline(Boyd et al, 2002)Consider (upper 80m) S over Lomo Ridge- 1995 ~ 34 psu – no CHL - 1997 ~ 33.55 psu- 1999 ~ 33 psu- 2000 ~ 33.3 psu – CHL returningWhat could be causing this??So far, this is EASTERN Arctic story,what about the Western ArcticWestern versus Eastern Arctic HaloclineEASTERN ARCTIC (ATLANTIC) HALOCLINE- less salinity range- saltier at surface- sharper bend in TS spaceWESTERN ARCTIC(PACIFIC) HALOCLINE- greater salinity range- fresher at surface- general Tmax above Tmin- very varied- (rich in nutrients)Adapted from Steele and Boyd 1998Shift of Pacific/Atlantic Front- use TS and chemistry to show Pacific Atlantic Front retreated from Lomo Ridge to Mendeleev Ridge by 1993JGR, 1996JGR, 2005Historic Russian Data- silicate profiles in central Makarov- Si max disappears in late 1980sBering Strait and the Chukchi SeaNutrient-rich Anadyr watersBering Shelf watersAlaskan Coastal Current (warm, fresh, seasonal)Siberian Coastal Current (cold, fresh, seasonal)Stagnation Zones over Herald and Hanna ShoalsTo first order, except for- cooling- input from coastal polynyas,Chukchi dominated by input through Bering StraitExport to Arctic ~Input through Bering StraitWoodgate et al, DSR, 2005, http://psc.apl.washington.edu/Chukchi.htmlCOLDERSALTIERRICHER IN NUTRIENTSWARMERFRESHERLOWER IN NUTRIENTSJGR, 2004ACW=Alaskan Coastal WatersBSW = summer Bering Sea WaterGeneric Pacific Water circulation Steele et al, 2004BUT- doesn’t always match Fram Strait outflow – is there a better tracer- how get the Pacific Water off from the Chukchi- change in pathway with change in Atmospheric state- shift of Pacific/Atlantic boundary from Lomonosov Ridge=Four main outflows1. Barrow Canyon 2. Central Gap3. Herald Canyon 4. Long Strait??= Most nutrients in West= Outflows move east & north= Seasonal & interannual variabilityin TS (thus density and equilibrium depth) and also in volume = TOPOGRAPHIC CONSTRAINTS(Potential Vorticity Conservation)- Taylor columns in Chukchi- flow ~ along isobaths eastwardBUT WE SEE PW GETS AWAY FROM TOPOGRAPHY= FRICTION (TOP or BOTTOM)= DENSITY DIFFERENCES- dense water outflows= WIND EFFECTS- upwelling and downwelling- undercurrents= EDDIES= INERTIAL and TIDAL OSCILLATIONS AND MIXINGLongStraitChukchi Sea OutflowChukchi slope velocity 2002-2003red=73 20N blue=73 37NChukchi Slope 2002-2003TS-properties73 20N- red 60m/70m water73 37N- cyan 60m/110m water- navy 100m/110m waterTemperature Maximum is December – March, i.e. advective from the southIntrusions of Atlantic Water in AutumnDense Water Outflow– e.g. from coastal polynyas(e.g. Martin et al, 2004)ICETemperatureICEThicknessWindXIceS flux as new iceDense water on shelfDense water flows down shelf as adescending plume,entraining water.(i.e. down, but not OUT)2002, JGR- can get the salinities,but volume is smallWind effectsWindXWindXUpwelling of deeper water- can come up canyon onto the shelf- cf Chukchi slope canyons, Barrow Canyon, and many othersIf initial stratification enough,can get undercurrent opposite to the wind (Yoshida Undercurrent)- cf Beaufort slopeisopycnal3rdOctober5thOctober Results of a strong westward windShip’s ADCP of the Beaufort slope current system(red= towards you)(Andreas Muncheow, UDel)Upwelling versus polynyas??Use Silicate to track Pacific Water in the Chukchi BorderlandCan we get this TS from Bering Strait??NO ... salinities are only near 34 psu in extreme winters, and then the waters are at freezing, not warmerBering StraitTS 1990-1991Woodgate et al, 2005Influence of shelf waters??Along the Chukchi Shelf, upwelling and diapycnal mixing of lower halocline waters and Pacific waters(Note ventilation by polynya waters couldn’t give this T-S structure)Do the volumes work out?Volume PW at 33.1 psu per year ~ 6x 10^12 m3/yr (0.6 Sv for 4 months)In Arctic ~ half pure, half mixed with AW (1:1)Thus need 3 x 10^12 m3/yr AW to be raised onto shelfObserved upwelling events in Barrow Canyon= 2-3 x 10^11 m3 per eventTherefore need 10 events and there are multiple wind events, and multiple canyonsSo – plausibleAlso, this ventilation rate is an order of magnitude higher than estimates of polynya