1. Koninklijk Nederlands Instituut voor ZeeonderzoekRoyal Netherlands Institute for Sea Research NIOZ is part of the Netherlands Organisation for Scientific Research (NWO) Variability of Denmark Strait Overflow Water Hendrik M. van Aken & M. Femke de Jong THOR meeting, November 2009, Paris

3. 2009 survey AR7E

4. Time series from repeat surveys AR7E

5. The DSOW in different years lies near isopycnal,   41.67 (±0.02) kg/m 3, but with varying -S combinations. Different DSOW sources?? Two main contrasts!!  minima since 1991

6. All near-bottom observations since 1991, between the ~2500 m isobaths. Transition from DSOW to NEADW.

7. The LOCO-2 mooring Temporal variation in DSOW s -DSOW f contrast

8. The LOCO-2 mooring Temporal variation in DSOW density

9. The LOCO-2 mooring Temporal variation in DSOW density Annual cycle as the dominant periodicity in density??

10. 5 years of high-frequency LOCO-2 observations also show the DSOW s -DSOW f contrast.

11. LOCO-3 shows the connecting water mass between DSOW s/f and the NEADW, with salinity bimodality.

12. LOCO-3 follows the DSOW s/f signal of LOCO-2 with a delay of ~1.5 month

13. But no apparent relation between the density variability at LOCO-2 and LOCO-3 LOCO-2: annual cycle LOCO-3: higher-frequency sloshing in canyon in Reykjanes Ridge?

14. Near parallel 5-year trends in density are found at both moorings

15. The 5 year trend at LOCO-2 contrasts the long- term (19 year) trend of DSOW from the AR7E repeat surveys.

16. Concluding Questions:  What is the cause of the observed DSOW s -DSOW f contrast? Something happening in Denmark Strait?  Why is there an annual signal in the density at LOCO-2; Plume dynamics or meteorology in Denmark Strait?  What causes the long-term trends in density, and do they tell us something about changes in the THC?  Are these signals also found further downstream?