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Atlantic Meridional Overturning Circulation Slowdown Causes Widespread Cooling In The Atlantic
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  1. Stuart A. Cunningham Scottish Association for Marine Science Atlantic Meridional Overturning Circulation Slowdown Causes Widespread Cooling In The Atlantic Christopher D. Roberts3, Eleanor Frajka-Williams2, William E. Johns4, Will Hobbs5, Matthew D. Palmer3, Darren Rayner1, David A. Smeed1, Gerard McCarthy1 1National Oceanography Centre Southampton,2University of Southampton, 3Met Office, Exeter, 4RSMAS, University of Miami, 5IMAS, Hobart. Stuart.Cunningham@sams.ac.uk

  2. A cold subtropical North Atlantic OHC error ~=0.2x1022 J

  3. Enhanced Ocean Data Assimilation and Climate Prediction EN3 v2a gridded objective analysis of quality-controlled sub-surface temperature observations (Ingleby and Huddleston 2007, http://www.metoffice.gov.uk/hadobs/en3/). Spatial and Temporal Pattern of Ocean Heat Content in the North Atlantic(1991-2010 seasonal cycle removed & 0 to 2000 m)

  4. OHC (1022 J) : Feb 2004

  5. OHC (1022 J) : Aug 2004

  6. OHC (1022 J) : April 2005

  7. OHC (1022 J) : Aug 2005

  8. OHC (1022 J) : Sept 2006

  9. OHC (1022 J) : May 2007

  10. OHC (1022 J) : Oct 2009

  11. OHC (1022 J) : March 2010

  12. OHC (1022 J) : Jan 2011

  13. OHC (1022 J) : Sept 2011

  14. Observing the AMOC and Associated Heat Flux 41°N Johns, W. E., et al., (2011). "Continuous, array-based estimates of Atlantic Ocean heat transport at 26.5°N." J. Clim. 24(10): 2429-2449. Hobbs, W. R. and J. K. Willis (2012). "Midlatitude North Atlantic heat transport: A time series based on satellite and drifter data." J. Geophys. Res. 117(C01008): doi:10.1029/2011JC007039.

  15. F’surface flux 0 m Subtropical Atlantic Heat Budget (0-2000m) S’26.5°N N’41.0°N 2000 m

  16. Meridional Heat Transport and Divergence

  17. Ocean Heat Content

  18. ERA-Interim surface flux anomalies

  19. Relative Heat Content Change Palmer & Haines (2009): Estimating oceanic heat content change using isotherms, J.Clim, 22,

  20. What generates the MLD (q>14°C) temperature anomalies?

  21. Summary Sustained cooling in upper 2 km of subtropical Atlantic between 2010-2012. OHC change partitioned equally between the seasonal mixed layer >14°C and deep ocean. Reduced AMOC at 26.5°N is the largest contributor to reduced MHT divergence. In seasonal mixed layer heat loss is due to atmospheric heat loss (60%) and MHT divergence (40%). Results emphasise the role for the ocean in the North Atlantic climate system on seasonal to interannual timescales and suggest a role for the AMOC in setting sub-surface temperature anomalies. These anomalies have previously been linked to re-emerging SST patterns and subsequent NAO anomalies.

  22. Need to do a bit about re-emergence/SST patterns and link to NAO (Taws). Then say we identify the OHC change due to divergence as responsible.

  23. OHC Errors

  24. Ekman and Geostrophic Heat Transport Variability

  25. Interannual Variability • What happened to the MOC in 2009-10? • Table of annual changes (Std of annual means):

  26. RAPID MOC: 2009-2010, Ekman constant • What happened to the MOC in 2009-10,not directly due to Ekman? • Table of annual changes (Ekman fixed): • Longer duration (18-month) slowdown of the MOC: • seen in the Gulf Stream, upper mid-ocean and LNADW.

  27. Gulf Stream, MOC, Ekman & Upper Mid-Ocean Transports (10-day & 3-month, low-pass filtered) Gulf Stream MOC Ekman Upper Mid-Ocean LNADW (3-5km) UNADW (1.1-3km) • MOC timeseries and related data products are available from www.noc.soton.ac.uk/rpdmoc • Data from individual instruments are available from www.bodc.ac.uk

  28. Meridional Heat Transport Time Series Johns, et al. (2011), Continuous array-based estimates of Atlantic Ocean Heat Transport at 26.5N, JClim

  29. Meridional Heat Transport at 26.5°N QGS→ Cable voltage calibrated for temperature transport, (Shoosmith et al., 2005) r = 0.94, σ = 0.1 PW QEk→ ECMWF ERA Interim wind stress (daily) • Reynolds SST (weekly) QWBW→ Directly calculated from moored CM’s/thermistors in Abaco WB array QINT→ Zonally-averaged interior transport profile from endpoint geostrophic moorings •Seasonally-varyinginterior hyrdographic climatology (Hydrobase, R. Curry) merged with argo data. Contribution to Qnet by spatially correlated v,T variability across interior from argo data..

  30. Ocean Heat Content

  31. Atlantic Ocean Heat Transport Estimates Residual Radiation Balance, Climatologies and Direct Estimates Coupled models (CM2.1, CCSM4) Radiation balance residual (NCEP,ECMWF,TF08)l Global hydro inverse (Ganachaud) Air-sea flux climatology (Large) RAPID & 41N: Direct RAPID @ 26.5°N 1.26±0.11 PW 04-09 Hobbs & Willis @ 41°N 0.48±0.11 PW 04-09 TF08 error bars

  32. Overturning and Gyre Heat Transport

  33. Stuart A. Cunningham Scottish Association for Marine Science, Oban Atlantic Meridional Overturning Circulation Slowdown Causes Widespread Cooling In The Atlantic Christopher D. Roberts3, Eleanor Frajka-Williams2, William E. Johns4, Will Hobbs5, Matthew D. Palmer3, Darren Rayner1, David A. Smeed1, Gerard McCarthy1 1National Oceanography Centre Southampton,2University of Southampton, 3Met Office, Exeter, 4RSMAS, University of Miami, 5IMAS, Hobart. Stuart.Cunningham@sams.ac.uk