GODAE OceanView-GSOP-CLIVAR workshop June Monitoring the Ocean State from the Observations Stéphanie Guinehut Sandrine Mulet Marie-Hélène Rio Gilles Larnicol Anne-Lise Dhomps

GODAE OceanView-GSOP-CLIVAR workshop June Introduction  Our approach : –Consists of estimating 3D-thermohaline and current fields using ONLY observations and statistical methods –Represents a complementary approach to the one developed by forecasting centers – based on model/assimilation techniques –“Observation based” component of the Global MyOcean Monitoring and Forecasting Center lead by Mercator Océan  Previous studies have shown the capability of such approaches : –In producing reliable ocean state estimates (Guinehut et al., 2004; Larnicol et al., 2006) –In analyzing the contribution and complementarities of the different observing systems (in-situ vs. remote-sensing) (2 nd GODAE OSE Workshop, 2009)

GODAE OceanView-GSOP-CLIVAR workshop June The principle Global 3D Ocean State [T,S,U,V,H] Weekly – [0-1500m] 24 levels [1/3°]  MyOcean V1 RT/RAN The productsThe methodThe observations Altimeter, SST, winds T/S profiles, surface drifters Guinehut et al., 2004 Guinehut et al., 2006 Larnicol et al., 2006 Rio et al., 2011 Intercomparison with independent data sets and model simulations Analysis of the ocean variability Observing System Evaluation + MDT estimate

GODAE OceanView-GSOP-CLIVAR workshop June Global T/S  Armor3D - Method 1 2 SLA, SST in-situ T(z), S(z) multiple linear regression 2 1 Armor3D T(z), S(z) optimal interpolation synthetic T(z), S(z) vertical projection of satellite data (SLA, SST) combination of synthetic and in-situ profiles T(x,y,z,t) =  (x,y,z,t).SLA steric +  (x,y,z,t).SST’ + T clim (x,y,z,t) S(x,y,z,t) =  ’(x,y,z,t).SLA steric + S clim (x,y,z,t)

GODAE OceanView-GSOP-CLIVAR workshop June Armor3D reanalysis Synthetic T’ – at 100m SSALTO-DUACS MSLA 1/3° weekly DT - 04/07/2007 NCEP Reynolds OI-SST 1/4° daily - 04/07/2007 Arivo climatology – July – T at 100 m

GODAE OceanView-GSOP-CLIVAR workshop June Armor3D reanalysis Synthetic T’ – at 100m Armor3D T’ Argo T’ In-situ observations – Coriolis data center

GODAE OceanView-GSOP-CLIVAR workshop June Armor3D - Hydrographic variability patterns  Temperature variability over the period (global zonal averaged) : ARMOR3DSCRIPPS SODA Synthetic  Very similar results for Synthetic/ARMOR3D/SCRIPPS  No bias introduced by the method  Very promising to study the variability of the period which suffers from poor in-situ measurements coverage

GODAE OceanView-GSOP-CLIVAR workshop June  Temperature variability from 1993 to 2008 (global zonal averaged) : Hydrographic variability patterns

GODAE OceanView-GSOP-CLIVAR workshop June Armor3D - Hydrographic variability patterns  Salinity variability over the period (global zonal averaged) : ARMOR3D SCRIPPS SODA Synthetic  Argo obs sys mandatory

GODAE OceanView-GSOP-CLIVAR workshop June Global U/V/H  Surcouf3D - Method Surcouf : Field of absolute geostrophic surface currents weekly - 1/3° Armor3D : 3D T/S fields weekly - 1/3° - [0-1500]m Surcouf3D 3D geostrophic current fields weekly ( ) 1/3° - 24 levels from 0 to1500m

GODAE OceanView-GSOP-CLIVAR workshop June Surcouf3D - Comparison with model outputs  Vertical section at 60°W, in 2006 Armor3D* Surcouf3D GLORYS Surcouf3D at 500m GLORYS at 500m * geost. current with level of no motion at 1500m

GODAE OceanView-GSOP-CLIVAR workshop June Surcouf3D - Validation of 1000-m currents  Global statistics over the Atlantic outside the equateur (10°S-10°N) Comparison between 3 different methods (Surcouf3D, GLORYS, Armor3D) and in-situ observations (ANDRO) at 1000 m over the 2006/2007 period (Taylor, 2001) skill score Meridional component Standard deviation (cm/s) Correlation coefficient SURCOUF3D ● SURCOUF3D (weekly, 1/3°) ▲ GLORYS = Mercator-Ocean reanalysis (weekly, 1/4°) Ferry et al., 2010 ♦ Armor3D = geostrophic current with level of no-motion at 1500m (weekly, 1/3°) ● ANDRO = 1000-m currents from drifting velocities from the Argo floats (≈10days, ≈50/100km) Ollitraut et al, 2010  Results are very similar for the zonal component

GODAE OceanView-GSOP-CLIVAR workshop June Surcouf3D - Validation  Comparison with GoodHope VM-ADCP observations from 14/02–17/03/2008 SURCOUF3D ADCP  Good correlation with independent in-situ obs.  Other time series to be compared ADCP obs courtesy of S. Speich Zonal velocities (cm/s) Meridional velocities (cm/s) 14/02/08 17/03/2008

GODAE OceanView-GSOP-CLIVAR workshop June Surcouf3D - Validation  Comparison with RAPID current-meters in the Western boundary current off the Bahamas from April 2004 to April °North 76.5°West FloridaAfrica SURCOUF3D RAPID (current meters) GLORYS  Good correlation with independent obs., and with GLORYS  Importance of in-situ T/S profiles obs at depth for the inversion of the current

GODAE OceanView-GSOP-CLIVAR workshop June Surcouf3D - AMOC variability at 25°N  Very consistent with Bryden et al, 2005  Hight inter-annual variability  Hard to distinguish a long-term trend Floride Strait Transport from electrical cable AMOC = Geost + Ekman + Florida (Surcouf3D, Bryden et al., 2005) Ekman Transport from wind stress ERAInterim Geostrophic Transport from 75°W to 15°W and from the surface to 1000m (Surcouf3D, Bryden et al., 2005)  Comparison with Bryden et al, 2005 (section at 24.5° from Africa to 73°W and at 26.5°N off Bahamas) (Bryden et al,2005)

GODAE OceanView-GSOP-CLIVAR workshop June Surcouf3D - AMOC variability at 26.5°N  Comparison with RAPID and GLORYS from April 2004 to December 2007 (monthly means + 12-month filtered)  Similar seasonal cycle  Amplitude differences ~ 10%  Higher variability in Surcouf than in Glorys that has to be further analyzed SURCOUF3D RAPID GLORYS

GODAE OceanView-GSOP-CLIVAR workshop June Conclusions / Perspectives Armor3D/Surcouf3D tools are very useful : to perform intercomparison exercices to study the interannual variability of the hydrographic patterns, the AMOC … Intercomparison studies will be continued between Armor3D and Surcouf3D and MyOcean global reanalysis Further study the ocean state (T/S variability, MOC, Heat/Salt transport) in key regions and for the periods Armor3D/Surcouf3D reanalysis are distributed as part of MyOcean

GODAE OceanView-GSOP-CLIVAR workshop June … …