2. 10/24/03search_osm_10_032 Abrupt Change in Deep Water Formation in the Greenland Sea: Results from Hydrographic and Tracer Time Series SEARCH Open Science mtg., October 03 P. Schlosser, J. Karstensen, D. Wallace, J. Bullister, and J. Blindheim CU/L-DEO, IfM Kiel, NOAA PMEL, IMR Bergen

3. 10/24/03search_osm_10_033 Outline Background Early hydrography tracer observations Tracer and hydrographic data from the 1990s Evolution of deep waters Evolution of intermediate waters Connection to outflow waters Summary

4. 10/24/03search_osm_10_034 Greenland Sea in the context of Atlantic THC Levitus salinity map AMAP

5. 10/24/03search_osm_10_035 Greenland Sea in the context of Nordic seas Red: warm, salty Atlantic Water; Blue: cold, fresh Arctic outflow Black: deep circulation Inflow (Sv): NA: ca. 8 Sv; Bering Strait: ca. 1 Sv Outflow (Sv): Near surface: ca. 3 Sv; Overflows: ca. 6 Sv

6. 10/24/03search_osm_10_036 Mean surface conditions

7. 10/24/03search_osm_10_037 Sections across the central Greenland Sea (75N; 6/99) 1.Cyclonic circulation 2.Doming of isopycnals 3.Polar/Arctic front 4.Relatively homogeneous deep water

8. 10/24/03search_osm_10_038 Evolution of tracer concentrations in surface waters

9. 10/24/03search_osm_10_039 Early Hydrography/tracer time series Boenisch et al., 1997

10. 10/24/03search_osm_10_0310 2000 m to bottom 200 to 2000 m Evolution of T/S and tracer properties Boenisch et al., 1997

11. 10/24/03search_osm_10_0311 Surveys during the 1990s Cruises: Johan Hjort; IMR Norway, Johan Blindheim 10 cruises 1991 to 2000

12. 10/24/03search_osm_10_0312 Hydrography/tracer time series during the 1990s

13. 10/24/03search_osm_10_0313 Evolution of deep water T/S properties

14. 10/24/03search_osm_10_0314 Evolution of deep water tracer properties

15. 10/24/03search_osm_10_0315 Background stratification versus features in convective cells. Conv. cells are characterized by temp. max. at the bottom of the feature. Imprints from deep convection

16. 10/24/03search_osm_10_0316 Evolution of tracer inventories Tracer inventories indicate formation of intermediate waters in 1994, 1999, and possibly 1992.

17. 10/24/03search_osm_10_0317 Evolution of T and S anomalies

18. 10/24/03search_osm_10_0318 During convection: Re-distribution of tracers No net mass transport After convection: Mass transport by eddies and meridional circulation Greenland Sea Sea ice may be important Convection and tracer profiles

19. 10/24/03search_osm_10_0319 Properties on overflow water isopycnals

20. 10/24/03search_osm_10_0320 Heat fluxes required to restore 1970’s conditions

21. 21 Summary Change in deep water formation rates 1.Abrupt change in DWF rate occurred around 1980 2.Reduction in DWF rate: ca. 80%; more or less constant since 1980 3.Greenland Sea gyre still on trend away from properties known from instrumental records. ‘Recovery’ needs significant forcing. Deep waters 1.Quasi-linear trends in T (10 mK yr -1 ) and S (1 ppm yr -1 ) 2.Advection of water from Arctic Ocean 3.Little influence of atmosphere (isolated from atm. Forcing on short time scales) Intermediate waters 1.Variability in formation 2.Warmer and fresher (sea ice plays little role) 3.Events: 94/95 and 99/00 (possibly 92/93) 4.Transport: 0.1 to 0.2 Sv (0.5 during conv. events)

22. 10/24/03search_osm_10_0322 Hydrography/tracer time series during the 1990s

23. 10/24/03search_osm_10_0323 Background stratification versus features in convective cells. Conv. cells are characterized by temp. max. and its depth.

24. 10/24/03search_osm_10_0324 GS variability Local Regional

25. 10/24/03search_osm_10_0325 GS variability Local Regional

26. 10/24/03search_osm_10_0326 Factors controlling GSDW Arctic outflow (quasi constant) Deep convection (sporadic) Connection to surface temperature?