1 THOR as of

What is it all about? NADW – North Atlantic Deep Water 1 Sv = 10 6 m 3 /s Atlantic Meridional Overturning Circulation

Core Theme 1 MOC Variability Core Theme 3 Observations Core Theme 2 Model Uncertainty Core Theme 5 Technological Advancements Core Theme 4 Prediction & Predictability 20 Years Prediction: THOR and its 5 Core Themes

Project Management and Coordination (UHAM) CT 1: Quantifying and modelling THC variability using palaeoclimate observations and simulations (MPI-M, MetO, UPMC, UiB, IFM-GEOMAR, NERSC, CNRS) CT 2: Assessing sources of uncertainty in ocean analyses and forecasts (DMI, MPI-M, MetO, UPMC, UiB, IFM-GEOMAR, NERSC) CT 3: Observations of the North Atlantic THC (UiB, UHAM, IFM-GEOMAR, HAV, MRI, NIOZ, NERC, SAMS, MPI-M) CT 4: Predictability of the Meridional Overturning Circulation (KNMI, MPI-M, MetO, ECMWF, UREAD, IFM-GEOMAR) CT 5: Technological Advancements for Improved near-realtime data transmission and Coupled Ocean-Atmosphere Data Assimilation (IFM-GEOMAR, UHAM, UiB, NERC, ECMWF, KNMI) Governing Board (GB) Scientific Steering and Executive Committee (SSEC) International Advisory Panel Gender Panel Project Structure

5 Universities | 9 Research Institutes | 6 Governmental Operational Institutions Université Pierre et Marie Curie Centre National de la Recherche Scientifique Commissariat a I’Energie Atomique Royal Netherlands Meteorological Institute Rocal Netherlands Institute for Sea Research University of Hamburg Max-Planck-Institute of Meteorology IFM-GEOMAR at University of Kiel University of Bergen Nansen Environmental Research Concil Finnish Meteorological Institute Danish Meteorological Institute MET Office UK ECMWF – European Centre for Medium-Range Weather Forecasts University of Reading Center for Environment, Fisheries and Aquaculture Science Natural Envirnment Research Concil Scottish Association for Marine Science Marine Research Institute Iceland Faroe Marine Research Institute

Core Theme 1: Understanding Variability Analysis of Millennium-scale numerical experiments and paleo-records Atlantic inflow into the Nordic Seas The observations and the model simulation show predominantly multidecadal-scale variability and a similar long-term evolution Otterå, Bentsen, Drange & Suo, 2010

Core Theme 1: On-going Work The figure shows how the vigor of Iceland-Scotland Overflow Water (ISOW) (, in red) (Mjell et al. in prep) and basin wide temperature (AMO in blue, after Gray et al., 2004) have co-varied over the past 400 years. i.e. Relation between newly observed overflow strength and the basin-wide temperature changes:

Core Theme 2: Assessing Model Uncertainties i.e. melting of the Greenland Ice Sheet, impact on the Ocean fresh water – salinity distribution after 30 years Input of 0.1 Sv around Greenland east & west west only east only Biastoch, 2010 Ocean reanalyses and observations, sensitivity experiments

Core Theme 2: On-going Work Passive tracer release along the coast of Greenland Working hypothesis: The effect of additional runoff on the convective activity in the interior Labrador Sea is weaker in models which resolves eddies. Coarser resolution models applying parameterizations which tend to cap the area with freshwater from the sides After 3.5 years

Collapse of convection in the LS The coarse simulation is less effected by additional freshwater due to lower initial overturning and lack of initial deep convection in the Labrador Sea Core Theme 2: On-going Work

Core Theme 3: Observing the AMOC

Core Theme 3: On-going Work Volume transport for deep western boundary current at the exit of the Labrador Sea ( ); J. Fischer (IFM-GEOMAR) Heat content of central Labrador Sea from K1 T time series ( ); J. Fischer (IFM-GEOMAR) Volume fluxes of MOC and mooring profiles of T,S at N ( ongoing); S. Cunningham (NOCS/NERC) Volume fluxes of FBC overflow ( ), IFR inflow ( ) and CTD standard sections; B. Hansen (FFL) Volume fluxes of inflow of Atlantic waters in FSC ( ), overflows at FSC and WTR ( ) and CTD standard sections ; T. Sherwin (SAMS) Volume transport of DSOW from Angmag-ssalik array and T,S time series ( ); D. Quadfasel (IFM-UHAM), S. Dye (CEFAS) Volume fluxes and T,S time series for Central Irminger Sea ( ); J. Fischer and J. Karstensen (IFM-GEOMAR) Volume fluxes in the Irminger Sea and CTD sections Between Greenland and Ireland ( ); H. van Aken (NIOZ) Volume transport of DSOW and EGC at Denmark Strait sill section ( ); D. Quadfasel (IFM-UHAM) Volume and heat fluxes of Atlantic waters at Hornbanki section ( ); S. Jónsson (MRI) Transport data sets Hydrography data sets

Core Theme 4: Prediction and Predictability + Data Model Synthesis = Hindcasts – ocean only Forecasts initialisation PREDICATE: Sutton, 2004Köhl pers. con. 2010

initial uncertainty forecast uncertainty reference forecast i.e. Result: Optimal perturbations reality ensemble forecasts Optimal perturbations for decadal climate predictions are: climate perturbations which grow most rapidly consistent with the observational uncertainties useful for:  efficient perturbations in ensemble forecasts  identifying regions where additional observations would be most valuable to improve predictions Core Theme 4: On-going work

Bergen CMEC-EARTHHadGEM1 IPSL CM4MPI Example optimal perturbations in temperature Ed Hawkins UREAD, in prep Core Theme 4: On-going work

Core Theme 5: Technological Advancements Real true data transmission from moorings Data assimilation in coupled models

Core Theme 5: On-going 1. Real true data transmission from moorings The Bergen System (accomplished)

Core Theme 5: On-going 1. Real true data transmission from moorings The Kiel System (testing)

Core Theme 5: On-going 2. Data assimilation in THOR coupled model coupling: replacement of seaice- and ocean- compartments of the PlanetSimulator by MITogcm plus seaice configuration: coarse resolution setup with an atmosphere on a T21 grid and 5 sigma levels, and the MITogcm on a 5.625º grid having the North Pole shifted to Greenland, using 15 vertical levels testing: coupled system with single CPU on a notebook, performance is approx. 30 model years/day