www.clivar.org

Ocean ReanalysisD. Stammer

• Continued development of ocean synthesis products and reanalysis; some now are truly global, including sea ice, multi-decadal; new EU Arctic reanalysis effort just started.

• Exploration of use of syntheses for initialization.

• Continuation on joint evaluation efforts and improvements.

• Reprocessing of input data sets and prior error information. • 8 Community White paper contributions to OceanObs’09.

• First coupled assimilation efforts exist; more developments are ongoing (K7; GFDL; KlimaCampus, ….).

Ocean synthesis/reanalysis

Ocean synthesis/reanalysis

Annual CLIVAR/GODAE Ocean Synthesis Workshops Intercomparison of products from multiple groups Evaluation of product quality and skill Identification of system strengths and weaknesses Definition of climate-relevant indices and standards for assessment GSOP participation in WCRP Earth System Initialization for Decadal Predictions Workshop, Nov 2009 – KNMI, Utrecht, The Netherlands.

GSOP participation in St. Michaels (MD) Workshop on: Decadal Climate Variability Decadal Climate Predictability and Prediction

WGOMD-GSOP Workshop on Decadal Variability, Predictability and Predictions: Understanding the Role of the Ocean, Boulder, Sept. 2010

Need for Climate-oriented Ocean Data Synthesis

Ongoing Ocean SynthesisOngoing Ocean Synthesis

• Several global ocean data assimilation products are available today that in principle can be used for climate studies. Basin panels were encouraged to enhance their usage.

• Underlying assimilation schemes range from simple and computationally efficient (e.g., optimal interpolation) to sophisticated and computationally intensive (e.g., adjoint and Kalman smoother).

• We need to evaluate the skill of each of those estimates in simulating the true ocean and for initialisation of predictions (EasyInit).

(Trenberth et al.)

SSH Error Sources: instrumental errors

(Trenberth et al.)

Improved Heat Content Estimate

Domingues et al. (2008)

Global Heat Content Anomaly (1022 J)

No Modelz-Level Model

EN3 DePreSys

MITMOMPOPOPA/NEMO

ERA40NCEP

Mercator URDG SODA GFDL GODAS K-7

HOPE

ECMWF INGV

3D-Var/OI 4D-Var.25ox.25o

1ox1o

2ox2o

CORE

GECCO

Bias corr.E-P.

Relax.

Relax.

Relax.Relax.QSCATGPCP

DATADATA

Example: The GECCO State Estimate

• Part of the ECCO Consortium Effort (see ecco-group.org).• Ocean synthesis, performed over the period 1952 through 2001 on

a 1º global grid with 23 layers in the vertical, using the ECCO/MIT adjoint technology (now extended to present globally).

• Optimization started from Levitus and NCEP forcing and uses state of the art physics modules (GM, KPP).

• The models adjoint (obtained using TAF) is used to bring the model into consistency with most of the available ocean observations over the full period by adjusting control parameters.

• So fare control parameters: initial temperature and salinity fields, surface forcing. Now also included: mixing parameters.

• Note: the final run is a free forward run.

Comparison GECCO - ObservationsComparison GECCO - Observations

Topex/Poseidon (1993-2001)GECCO Model (1992-2001)

(Köhl et al., 2007)

Total Trend 1992 – 2001 (cm)

Halosteric Trend

Thermosteric Trend

Steric Trend

GECCO

ECCO-SIO/50y + Ref.

Bryden et al. (2005)

Ocean synthesis/reanalysis

12m-rm seasonal anom: NATL Averaged temperature over the top 300m

1950 1960 1970 1980 1990 2000Time

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

ukdpukoicfcs2cfas2ecco50y

gfdlsodaecmfaecmfcukgs

ingvmri-eccoSIOcfasamct2

mct3eccoJPLaeccoJPLceccoMITGMAO

sdv ensm = 0.164s/n ensm = 1.620

sdv all = 0.206s/n all = 2.028

spread = 0.101

N. Atlantic Temp(0-300 m)

WCRP enablinginitialized predictions

Global Synthesis and Observations PanelIntercomparison of the Indonesian Throughflow (ITF) Transport Estimated by

Ocean Data Assimilation (ODA) Products (Joint GSOP-IOP activity)

• No substantial weakening associated with the 1976 “climate shift”: Wainwright et al. (2008) reported a 2.5-Sv reduction based on an analysis of IX1 XBT data (Fremantle – Sunda Strait).

• Decadal signals of 10-15 year periods.• A consistent strengthening during 1992-2000: consistent with observed wind and SSH

Five-year low-pass ITF transport

anomaly (color curves) and their

ensemble average (14 synthesis

products) (black curve)

SODAECMWF GECCO

SODA ECMWFGECCO

Trend in Sea Level 1992-2001 (cm/yr)

SODA

ECMWF GECCOSODA

ECMWF

ECMWFGECCO

GECCO

Trend in Sea Level 1962-2001 (cm/yr)

Next GSOP Efforts

• Chairs: B. Sloyan, K. Haines (WOAP member), D. Stammer

• Implementation of OO’09 Outcome (jointly with OOPC)

• Reanalaysis of global historic hydrography

• Reanalysis of XBT data

• Analyze global budgets and sea level

• EazyInit: Providing initial conditions for seasonal- to decadal predictions.

• Improving initial conditions and initializations.

• Preparing for Coupled Data assimilation

www.clivar.org

Thank you