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Variability of Denmark Strait Overflow Water

Variability of Denmark Strait Overflow Water. Hendrik M. van Aken & M. Femke de Jong THOR meeting, November 2009, Paris. 2009 survey AR7E. Time series from repeat surveys AR7E. q minima since 1991.

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Variability of Denmark Strait Overflow Water

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

  2. 2009 survey AR7E

  3. Time series from repeat surveys AR7E

  4. q minima since 1991 The DSOW in different years lies near isopycnal, s341.67 (±0.02) kg/m3, but with varying q-S combinations. Different DSOW sources?? Two main contrasts!!

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

  6. The LOCO-2 mooring Temporal variation in DSOWs-DSOWf contrast

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

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

  9. 5 years of high-frequency LOCO-2 observations also show the DSOWs-DSOWf contrast.

  10. LOCO-3 shows the connecting water mass between DSOWs/f and the NEADW, with salinity bimodality.

  11. LOCO-3 follows the DSOWs/f signal of LOCO-2 with a delay of ~1.5 month

  12. 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?

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

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

  15. Concluding Questions: • What is the cause of the observed DSOWs-DSOWf 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?

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