Coastal Processes and Arctic Climate Change

1. Coastal Processes and Arctic Climate Change Are they resolved? Do they matter? How do they scale? Andreas Münchow College of Marine Studies University of Delaware Collaborators: Drs. Falkner, Garvine, Melling, Weingartner

2. Hypotheses/Conclusions Large, abrupt pulses of freshwater discharges do not disturb the thermohaline circulation substantially; Freshwater driven flows scale with the internal deformation radius L~10-km (“eddy” scale); Scaling implies small across-shore (~10-km) and long along-shore (~1000-km) correlation scales; “Measured” (and modeled) freshwater fluxes do not resolve relevant scales; Nares Strait mooring array designed to resolve the internal deformation radius, freshwater fluxes, and dynamics.

3. global Coastal Processes and Arctic Climate Change: • Insulation of the Arctic ice-cover from warm Atlantic water at depth, i.e., “maintenance of the Arctic halocline” • Arctic freshwater and the global thermohaline circulation (nonlinear, multiple equilibria) How to move water across sloping topography?

4. Hypotheses/Conclusions Large, abrupt pulses of freshwater discharges do not disturb the thermohaline circulation substantially;

5. Greenland Ice Core Data oxygen isotopes 18O ~ T temperature Today’s climate WARM 18O COLD Climate of last 10,000 years appears most anomalous. Figure from Alley et al. (2001)

6. 100 mSv Overturning Circulation Hysteresis Loop of Climate Change Stommel (1961) Nonlinear response of thermohaline circulation to freshwater pertubations WARM Caveats: • Location of current climate? • 100-500 year duration • Distance to convection sites COLD Rahmstorf (2000)

7. 100 mSv Overturning Circulation Freshwater Flux Alley (2001) Hysteresis Loop of Climate Change Stommel (1961) WARM COLD Rahmstorf (2000)

8. Freshwater Flux: ∫ u(s-s0)/s0 dA Arctic Rivers Bering Strait Davis Strait Lena River Amazon River Lake Ontario Arctic Ice Volume Lake Agassiz* 110 mSv 70 mSv 100 mSv 17 mSv 200 mSv 9 mSv >1,000 mSv 3,800 km3/y 2,200 km3/y 3,000 km3/y 510 km3/y 6,300 km3/y 270 km3/y 30,000 km3 >30,000 km3/y (*) glacial lake dammed by Laurentian ice sheet burst ~8200 BP (Barber et al., 1999, Nature) 0.1 Sv = 0.1106 m3/s = 100 mSv = 3,150 km3/year

9. Greenland Ice Core Data oxygen isotopes 18O ~ T temperature Today’s climate WARM 18O Lake Agassiz discharge COLD Younger Dryas Climate of last 10,000 years appears most anomalous. Adapted from Alley et al. (2001)

10. √∆/0 g D / f ~ 10 km  D +∆ Hypotheses/Conclusions Large, abrupt pulses of freshwater discharges do not disturb the thermohaline circulation substantially; Freshwater driven flows scale with the internal deformation radius L (“eddy” scale); f is Coriolis “force”

11. L D Nares Strait Hydrography, Aug.-2003 L Density “derived” velocity view from Greenland across Nares Strait Temp. Salinity Canada Greenland Pics-August Pics-April

12. Velocity:Radars + Sonars David Huntley (UDel) with “sonar” in Aug. 2003 Radars send and receive electromagnetic waves (radio, police) Sonars send and receives acoustic waves (sound, whales) Same physics.

13.    L D D east west • • t0 t0+16 hrs Barrow Canyon Velocity Section: Synoptic velocity observation in Barrow Canyon, Alaska (view is to the south): The flow scales with the internal deformation radius, about 5-km. The flow is also unsteady. Münchow and Carmack (1996)

14. I II III Eddies in the ArcticSept.-22, 2004 I II III D L USCGC Healy 75-kHz ADCP

15. Interaction of wind- and buoyancy forced motions L D Salinity Fresh riverine water turns right at the coast. Münchow and Garvine (1993)

16. Hypotheses/Conclusions Large, abrupt pulses of freshwater discharges do not disturb the thermohaline circulation substantially; Freshwater driven flows scale with the internal deformation radius L~10-km (“eddy” scale); Scaling implies short across- (~10-km) and long along-shore (~1000-km) correlation scales

17. Ward Hunt Ice Shelf Arctic Ocean Ice shelf ~ 4 km3 fresh water and unique ecosystem lost from dammed epishelf lake in Disraeli Fjord 1999-2002 Ellesmere Island Mueller et al. (2003) Disraeli Fjord crack

18. 1964 1962 Ward Hunt Ice Shelf 1963 Nutt (1966): The drift of ice island WH-5

19. Hudson Strait LABRADOR NASA Labrador Shelf Moving ice on the Labrador shelf indicates trapping of fresh water and ice on the shelf deep convection site winter 1997 (Pickart et al., 2002)

20. North (cm/s) East (cm/s) Labrador Sea Labrador Crossing the Labrador Current, July-23, 2003 eastward Velocity Velocity southward shelf Depth basin cold cool warm Temp. fresh salty Sal. Time (hours)

21. ?? ??? Hypotheses/Conclusions Large, abrupt pulses of freshwater discharges do not disturb the thermohaline circulation substantially; Freshwater driven flows scale with the internal deformation radius L~10-km (“eddy” scale); Scaling implies small across-shore (~10-km) and long along-shore (~1000-km) correlation scales; “Measured” (and modeled) freshwater fluxes do not resolve relevant scales Chapman and Beardsley (1989) adapted by Khatiwala et al. (1999)

22. Davis Strait 3-year Mean1987-1990 ~150-m ~300-m with 95% confidence levels for speed and direction ~500-m “Ross” data (Tan et al., 2005)

23. Velocity normal to Davis Strait mooring section: Volume flux: 1.5 ± 0.8 Sv Freshwater flux: 75 ± 38 mSv 2.3Sv 3-year mean velocity plus 95% confidence Baffin Island Current West Greenland Current 3-year mean velocity minus 95% confidence 0.7Sv   3-year mean velocity (contours) over 1987-1990 salinity (color) 1.5Sv EOF Analyses

24. Davis Strait Northward Flow @ 150-m (“surface”) Annual harmonic + Semi-annual harmonic + record mean Baffin Island Current West Greenland Current

25. Greenland Ice Sheet 5-km NASA/USGS Baffin Bay Retreat of Jakobshavn Isbræ West-Greenland

26. Hypotheses/Conclusions Large, abrupt pulses of freshwater discharges do not disturb the thermohaline circulation substantially; Freshwater driven flows scale with the internal deformation radius L~10 km (“eddy” scale); Scaling implies short across-shore (~10-km) and long along-shore (~1000-km) correlation scales; “Measured” (and modeled) freshwater fluxes do not resolve relevant scales; Nares Strait mooring array designed to resolve the internal deformation radius, freshwater fluxes, and dynamics

27. Arctic Ocean Greenland NASA 2002/223 Petermann Glacier Humbold Glacier Canadian Archipelago Throughflow Study (CATS):

29. L L   S Canada Greenland Kennedy Channel Hydrography, Aug.-2003 Geostrophic current D view from Greenland across Nares Strait D Pics-August Pics-April

30. Nares Strait South (Kennedy Channel) Salinity s Velocity  ∫ u dA Freshwater Flux/unit area  ∫ u(s-s0)/s0 dA

31. Wind   Across-channel flow  Along-channel flow .html Pics-April Pics-August * Currents @ 100-m

32. Hypotheses/Conclusions Large, abrupt pulses of freshwater discharges do not disturb the thermohaline circulation substantially; Freshwater driven flows scale with the internal deformation radius L~10-km (“eddy” scale); Scaling implies small across-shore (~10-km) and long along-shore (~1000-km) correlation scales; “Measured” (and modeled) freshwater fluxes do not resolve relevant scales; Nares Strait mooring array designed to resolve the internal deformation radius, freshwater fluxes, and dynamics.