1. Towards a High-Resolution Global-Ocean and Sea-Ice Data Synthesis Seminar presented at UC, Irvine on May 2, 2007 Dimitris Menemenlis Jet Propulsion Laboratory Outline: Background and Motivation ECCO2 project description Some early science results http://ecco2.org/

2. Summary of 22-23 January 2007 ECCO2 meeting Overview and Motivation ECCO, ECCO-GODAE, ECCO2 (Wunsch, MIT) The only way to understand the complete, global, time- evolving ocean circulation is to use all available data and all available theory. ECCOn seeks the best possible estimate of the time-evolving ocean circulation, its influence on climate, chemistry, biology, etc., understanding of predictability, and determination of what we do not understand. A two+ generation problem! ECCO2 and NASA satellite missions (Fu, JPL) Observations of mesoscale and sub-mesoscale ocean variability are a key requirement for understanding regional and global climate processes. For this reason, wide swath altimetry has been endorsed by the NRC Decadal Survey as a possible new NASA mission. ECCO2 provides a framework for utilizing high-resolution data from existing and future NASA satellite missions. Estimated sea level trend, spatial mean removed (Wunsch, Ponte, and Heimbach, 2007). Ground tracks of TOPEX/Jason tandem mission superimposed on satellite imagery of sea surface temperature.

3. ECCO2: High-Resolution Global-Ocean and Sea-Ice Data Synthesis MIT Marshall, Heimbach, Hill Wunsch JPL Fu, Kwok, Lee Menemenlis Zlotnicki GSFC Rienecker Suarez ARC Henze, Taft HARVARD Tziperman GFDL Adcroft ARGONNE Hovland, Utke Objective: synthesis of global-ocean and sea-ice data that covers the full ocean depth and that permits eddies. Motivation: improved estimates and models of ocean carbon cycle, understand recent evolution of polar oceans, monitor time-evolving term balances within and between different components of Earth system, etc. Velocity (m/s) At 15 m depth

4. Summary of 22-23 January 2007 ECCO2 meeting Assimilation and Modeling Towards an ECCO2 release (Menemenlis/Zhang, JPL) A first least squares minimization of the global-ocean and sea-ice cube sphere (CS510) model resulted in a 64% decrease of cost function wrt temperature and salinity climatologies. These state estimates are already being used in a host of science applications Eddy permitting state estimation (Mazloff/Heimbach, MIT) Adjoint method state estimation in the presence of vigorous mesoscale eddy variability has been shown to be possible in a regional, high-resolution, Southern Ocean model configuration. ECCO2 high resolution modeling (Hill/Menemenlis/Henze) High-resolution global-ocean and sea-ice simulations are being used to estimate error statistics, to experiment with multiscale assimilation, to improve parameterizations of unresolved processes, and to drive the development of petabit/petaflop infrastructure.

5. Using model Green’s functions to fit an eddy-permitting global- ocean and sea-ice model to satellite and in-situ data 1992 20022005 140Sv 170Sv Drake Passage Transport Baseline Optimized A Green’s function approach is being used to fit a high-resolution configuration of the MITgcm to satellite and in-situ ocean and sea ice data. Top panel shows temperature difference in top 700 m between WGHC climatology and a 1992-2002 baseline integration driven by NCEP. Bottom panel shows temperature difference from WGHC for an integration whose initial conditions, surface boundary conditions, and internal model parameters have been calibrated using 30 forward sensitivity integrations (H. Zhang). This first optimization improves Southern Ocean circulation and stratification (M. Schodlok) … … but it degrades Arctic Ocean sea ice distribution and freshwater budget (R. Kwok and A. Nguyen). RGPS RGPS Baseline Optimized November 1997 April 1998 April 1998 April 1998 Optimized minus Baseline time-mean wind difference

6. http://ecco2.jpl.nasa.gov/products/output/cube/ Towards obtaining the first optimized solution, some fifty forward sensitivity integrations have been computed and are available for analysis.

7. 25ºS to 78ºS 1/6º horizontal grid spacing 42 depth levels with partial cells i.e., 1/3 grid points of global config. KPP and GM-Redi Bulk formulae and sea-ice model Southern Ocean State Estimate Mazloff and Heimbach, MIT Currently optimizing year 2005. First guess initial conditions and open boundary conditions derived from coarse-resolution ECCO solution. First guess atmospheric state from NCEP reanalysis. Data constraints: mean and time- variable sea surface height, sea-ice concentration, in-situ temperature and salinity profiles, sea surface temperature, and hydrographic climatology.

8. Cost associated with misfit to sea surface height anomaly Iteration 4; Mean = 1.1 Cost change Iteration 4 - Iteration 0

9. 1/4°1/8° 1/16° 1/4°1/8°1/16° Investigating global ocean model solution convergence Hill, Menemenlis, Ciotti, and Henze. Investigating solution convergence in a global ocean model using a 2048- processor cluster of distributed shared memory machines. J. Scientific Programming, 2007.

10. Depth of ocean surface turbulent mixing layer

11. Summary of 22-23 January 2007 ECCO2 meeting Early User Applications Subtropical mode water (Maze, MIT) Eddy propagation velocity (Fu, JPL) GRACE data constraints (Zlotnicki, JPL) Errors estimates (Forget, MIT) Eddy parameterizations (Ferreira, MIT) Arctic freshwater budget (Condron, WHOI) Arctic sea ice budget (Kwok, JPL) Sea ice data/model comparison (Nguyen, JPL) Carbon cycle modeling (Manizza, MIT) Eddy variability in Indian Ocean (Lee, JPL) Darwin project (Hill, MIT) Southern Ocean (Schodlok, JPL) MITgcm assimilation efforts (Cornuelle, SIO) Adjoint assimilation efforts (Edwards, UCSC )

12. Mode water formation (Marshall, Maze, and Hill, MIT) Objective is to study the dynamics of eighteen-degree mode water formation in the North Atlantic through analytical, numerical and observational approaches. Marshall (2005). CLIMODE: a mode water dynamics experiment in support of CLIVAR. Clivar Variations, vol.3, pp. 8-14.

13. Eddy sea surface variability and propagation velocity from altimetry cm 10 km/day Observing and Modeling Ocean Eddies Containing 90% of the kinetic energy in the ocean, ocean eddies (storm of currents) with scales from 10-100 km, are difficult to observe and simulate. Using data from TOPEX/Poseidon, Jason, and ERS radar altimeters, the energy level and propagation velocity of eddies were estimated and compared to a high-resolution simulation from the MIT-JPL ECCO Model. Shown below is an example in the Argentine Basin. L-L. Fu & D. Menemenlis ECCO2 simulation cm Coastal tides not included in the model

14. Estimating global hydrographic variability (Forget and Wunsch, MIT) Objective is to estimate the three-dimensional global oceanic temperature and salinity variability, omitting the seasonal cycle, both as a major descriptive element of the ocean circulation and for use in the error estimates of state estimation. Forget and Wunsch. Estimated global hydrographic variability. J. Phys. Oceanogr., 2007. Variance of T at 200m (left) and 400m (right) in ( o C) 2 as estimated from the data (upper) and as simulated by an ECCO2 simulation (lower).

15. Total eddy heat transport Eddy heat transport in top 200m Total meridional heat transport G&W Most of the meridional eddy heat flux is achieved in the top 200m of the ocean! by diabatic eddies! David Ferreira Not yet adequately parameterized in large- scale coarse-resolution models

16. ~3400 km3/yr (0.1 Sv) freshwater added from 54 arctic rivers for 11 years into cube 47. Approx. 60% of discharge is from May-July Surface salinity anomalies (cube 47-cube 43) (negative = fresher) River discharge penetrating into interior. 1992 2002 Mackenzie Ob and Yenisey Lena A. Condron and P. Winsor, WHOI

17. Interpretation of ICESat altimetric and reflectivity profiles Kwok (JPL), et al. Objective is to provide an assessment of the ICESat altimeter for studying the Arctic Ocean and to examine the magnitude of the large- and small-scale expressions of geophysical processes embedded in the elevation profiles. Kwok, Cunningham, Zwally, Yi (2006). ICESat over Arctic sea ice: Interpretation of altimetric and reflectivity profiles. J. Geophys. Res., vol. 111, doi:10,1029/2005JC003175.

18. Synthesis of the Arctic System Carbon Cycle McGuire (Fairbanks), Follows, Manizza (MIT), et al. Objective is to study Arctic region carbon cycle, including (a) exchanges between marine and terrestrial carbon pools and (b) possible exchanges between these large carbon reservoirs and the atmosphere. ECCO2 solutions will be used to drive offline carbon/biogeochemistry models leading to improved estimates and models of air-sea-land-ice exchanges of CO2 in the presence of realistic eddying flows and with active biological and chemical processes.

19. Prochlorococcus analogs Synechococcus & small eukaryotes Diatoms Other large eukaryotes Darwin project (Follows and Hill, MIT)

20. Summary ECCO2 project aims to produce increasingly accurate syntheses of all available global-scale ocean and sea-ice data at resolutions that start to resolve ocean eddies and other narrow current systems. A first public ECCO2 ocean state estimate, obtained using model Green’s functions, is scheduled for this summer. Adjoint state estimation in the presence of vigorous eddying circulation has been successfully demonstrated. A number of early user projects have started using pre-release ECCO2 solutions. http://ecco2.jpl.nasa.gov/products/