THOR Presented by Doug Smith (MET OFFICE) Project coordinator: Detlef Quadfasel (UHAM)

Arctic Ice Cover during Winter 3000 km < 1000 km Winter ice boundaries

Population in the North ~ 400 Mio ~ 40 Mio ~ 4 Mio

Seasonal Ice Cover

Decadal Variability - Trends ?

Ocean Circulation carries Heat to the North … and returns fresh water south Shallow Circulation Deep Circulation

North Atlantic Thermohaline Ocean Circulation and its Impact on Climate: Thermohaline Overturning – at Risk ?

Facts and Figures  FP 7 Collaborative Project – Large Scale  Project lifetime: 4 years, December 2008 – November 2012  Research focus: Stability of the ThermoHaline Circulation  Participants: 20 participating institutions from 9 European countries  5 Core Themes, 12 Work Packages  Project cost: million Euro  EU Funding: 9.27 million Euro

Core Theme 1 MOC Variability Core Theme 3 Observations Core Theme 2 Model Uncertainty Core Theme 5 Technological Advancements Core Theme 4 Prediction & Predictability What is it all about? THOR and its 5 core themes NADW – North Atlantic Deep Water 1 Sv = 10 6 m 3 /s

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-real-time 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

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 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 and heat fluxes of Atlantic waters at Hornbanki section ( ); S. Jónsson (MRI) Transport data sets Hydrography data sets Datasets regularly updated, accessible through project homepage Volume transport of DSOW and EGC at Denmark Strait sill section ( ); D. Quadfasel (IFM-UHAM)

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

Core Theme 4: On-going work – your input?

Core Theme 5: Technological Advancements Real true data transmission from moorings: the Bergen and Kiel system Data assimilation in coupled models: THOR

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