Atlantic Meridional Overturning Circulation Slowdown Causes Widespread Cooling In The Atlantic Stuart A. Cunningham Scottish Association for Marine Science [email protected]Christopher D. Roberts 3 , Eleanor Frajka-Williams 2 , William E. Johns 4 , Will Hobbs 5 , Matthew D. Palmer 3 , Darren Rayner 1 , David A. Smeed 1 , Gerard McCarthy 1 1 National Oceanography Centre Southampton, 2 University of Southampton, 3 Met Office, Exeter, 4 RSMAS, University of Miami, 5 IMAS, Hobart.
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Atlantic Meridional Overturning Circulation Slowdown Causes Widespread Cooling In The Atlantic
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Atlantic Meridional Overturning Circulation Slowdown Causes Widespread Cooling In The Atlantic
Stuart A. CunninghamScottish Association for Marine Science
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.
OHC error ~=0.2x1022 J
A cold subtropical North Atlantic
Spatial and Temporal Pattern of Ocean Heat Content in the North Atlantic
(1991-2010 seasonal cycle removed & 0 to 2000 m)
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/).
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.
What generates the MLD (q>14°C) temperature anomalies?
Summary
1. Sustained cooling in upper 2 km of subtropical Atlantic between 2010-2012.2. OHC change partitioned equally between the seasonal mixed layer >14°C and deep
ocean.3. Reduced AMOC at 26.5°N is the largest contributor to reduced MHT divergence.4. In seasonal mixed layer heat loss is due to atmospheric heat loss (60%) and MHT
divergence (40%).5. 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.
6. These anomalies have previously been linked to re-emerging SST patterns and subsequent NAO anomalies.
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.
OHC Errors
Ekman and Geostrophic Heat Transport Variability
Interannual Variability
What happened to the MOC in 2009-10?
Table of annual changes (Std of annual means):Layer 2004-2008 2009 (change)
Mean [Sv] Std [Sv] Mean [Sv]
MOC 18.1 0.88 12.2 (-5.9)
Gulf Stream 31.8 0.26 30.7 (-1.1)
Ekman 2.9 0.36 1.1 (-1.8)
Upper mid-ocean -16.6 0.95 -19.6 (-3.2)
UNADW (1100-3000m) -11.9 0.18 -10.7 (1.2)
LNADW (3000-5000m) -7.8 0.69 -3.8 (4.0)
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):
Layer 2004-2008 2009 (change)
Mean [Sv] Std [Sv] Mean [Sv]
MOC 18.7 0.89 14.3 (-4.4)
Gulf Stream 31.8 0.26 30.7 (-1.1)
Ekman 3.6 0.0 3.6 (0)
Upper mid-ocean -16.7 0.91 -19.9 (+3.2)
UNADW (1100-3000m) -12.2 0.32 -11.5 (-0.7)
LNADW (3000-5000m) -8.0 0.66 -4.7 (-3.3)
Longer duration (18-month) slowdown of the MOC:seen in the Gulf Stream, upper mid-ocean and LNADW.
• 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
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.