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Deep circulation and meridional overturning

Deep circulation and meridional overturning. Steve Rintoul and many others …. Outline. Significance of the deep circulation and meridional overturning Progress in last decade Remaining challenges A strategy for observations of the deep ocean. Meridional overturning circulation.

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Deep circulation and meridional overturning

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  1. Deep circulation and meridional overturning Steve Rintoul and many others ….

  2. Outline • Significance of the deep circulation and meridional overturning • Progress in last decade • Remaining challenges • A strategy for observations of the deep ocean CSIRO. OceanObs09 Venice September 2009

  3. Meridional overturning circulation Lumpkin and Speer CSIRO. OceanObs09 Venice September 2009

  4. Meridional overturning circulation Speich (2009) adapted from Lumpkin (2007) CSIRO. OceanObs09 Venice September 2009

  5. Significance of the deep ocean and MOC • The MOC is the primary mechanism responsible for transport and storage of heat, freshwater and carbon and the resupply of nutrients. • Variations in the MOC are likely to have consequences for climate, both in present and future climates. • The MOC is a three-dimensional circulation spanning the full-depth global oceans. Therefore our observations of the MOC must extend throughout the full-depth of the ocean. • Changes in the deep ocean make a significant contribution to budgets of carbon, freshwater and heat (and hence sea-level rise). • Changes in the overturning circulation will impact on ecosystems by changing the nutrient content and carbon saturation state of surface waters. CSIRO. OceanObs09 Venice September 2009

  6. Progress in the last decade • First demonstration of sustained measurements of the MOC at 26.5N in the Atlantic. Provides evidence for substantial variability in MOC and deep ocean circulation. • Documented changes in heat, freshwater and carbon throughout the full ocean depth: link between surface climate and the deep ocean is stronger than suspected. • Showed that the deep ocean makes a significant contribution to changes in ocean heat content and sea-level rise. • First direct velocity measurements of a number of deep outflow pathways. • Deeper appreciation of role of the MOC in biogeochemical budgets (both sequestration and outgassing). • Deeper appreciation of role of the MOC and deep circulation in low-frequency climate variability. CSIRO. OceanObs09 Venice September 2009

  7. Projected slowing of Atlantic MOC CSIRO. OceanObs09 Venice September 2009

  8. MOC variability at 26.5N CSIRO. OceanObs09 Venice September 2009

  9. Changes in deep temperature (western Atlantic) Johnson and Doney (2006) CSIRO. OceanObs09 Venice September 2009

  10. Changes in salinity of Antarctic Bottom Water CSIRO. OceanObs09 Venice September 2009

  11. Anthropogenic carbon storage in the deep ocean Wanninkhof et al. (2009) CSIRO. OceanObs09 Venice September 2009

  12. MOC influence on Atlantic SST Latif CSIRO. OceanObs09 Venice September 2009

  13. Observing the deep ocean and MOC • Need to observe transport and inventory in the deep ocean. • Transport strategy: • Direct velocity measurements in boundary current (current meters, PIES, cables, pressure gauges) • Ekman contribution calculated from winds (eg QuikScat) • End-point monitoring of geostrophic flow • Altimetry and gravity measurements • Inventory strategy: • Repeat deep hydrography (with tracers; ie GOSHIP) • More rapid repeat hydro in overflows and main pathways • Broad-scale, long-duration deep moorings with data transfer • Deep floats CSIRO. OceanObs09 Venice September 2009

  14. Repeat hydrography CSIRO. OceanObs09 Venice September 2009

  15. Proposed AMOC observing system Add figure of RAPID array CSIRO. OceanObs09 Venice September 2009

  16. Global-scale deep observations Velocity measurements Deep water property moorings Deep carbon observations CSIRO. OceanObs09 Venice September 2009

  17. Measuring the southern limb of the deep overturning CSIRO. OceanObs09 Venice September 2009

  18. Data capsule for long-duration moorings CSIRO. OceanObs09 Venice September 2009

  19. Summary: need for deep ocean observations • To determine the MOC, its variability and its influence on climate • To close the planetary energy budget • To determine rates and mechanisms of sea-level rise • To determine the global budgets of carbon and nutrients and their sensitivity to change • To constrain ocean state estimates (including errors) • To understand the dynamics and nature of the global-scale ocean circulation, including response to forcing and modes of variability • To test and develop models, proxies and satellite data (eg gravity) CSIRO. OceanObs09 Venice September 2009

  20. Summary: a strategy for deep ocean observations • Build on established sites and technologies • Moored arrays in deep boundary currents • End-point monitoring for cost-effective measurements of basin-scale, full-depth flows • Repeat full-depth hydrography with tracers (including enhanced measurements near dense water outflows) • Broad-scale, inexpensive moorings for water properties Technology advances needed: • Deep floats • Data capsules for long duration moorings • Biological and biogeochemical sensors CSIRO. OceanObs09 Venice September 2009

  21. Contact Us Phone: 1300 363 400 or +61 3 9545 2176 Email: enquiries@csiro.au Web: www.csiro.au Thank you CSIRO Marine and Atmospheric Research Wealth from Oceans Flagship Antarctic Climate and Ecosystems Cooperative Research Centre Steve Rintoul steve.rintoul@csiro.au

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