Steffen M Olsen, Polar Oceanography, DMI, Copenhagen DK

1. Trieste, 1-2 October 2013 NACLIM Core Theme 3: People • GEOMAR (6) • MojibLatif (CT/WP lead) • Wonsun Park • Thomas Martin • Fritz Krüger • MPG (2) • Johann Jungclaus • KatjaLohmann • UHAM (1) • Detlef Stammer • Armin Köhl • Xueyuan • DMI (7) • Steffen M. Olsen (CT/WP lead) • Jacob L. Høyer • GormDybkjær • TorbenSchmith Steffen M Olsen, Polar Oceanography, DMI, Copenhagen DK

2. Trieste, 1-2 October 2013 NACLIM Core Theme 3: Structure Initialization of prediction systems with ocean observations WP 3.2 Steffen M. Olsen WP 3.1 MojibLatif Suitability of the ocean observing system components for initialization Impact of Arctic initialization on forecast skill Steffen M Olsen, Polar Oceanography, DMI, Copenhagen DK

3. Trieste, 1-2 October 2013 NACLIM Core Theme 3: WP 3.1 • Objectives • Investigate and quantify the benefit of different components of the ocean observing system for prediction systems (decadal) • Identify necessary enhancements and potential reductions in the present system WP 3.1 Suitability of the ocean observing system components for initialization • Methodology • Perfect model approach, hindcast experiments using the Kiel Climate Model • Re-start simulations with truncated ocean initial conditions corresponding to different ocean regions and observing systems Steffen M Olsen, Polar Oceanography, DMI, Copenhagen DK

4. Trieste, 1-2 October 2013 NACLIM Core Theme 3: WP 3.1 Deliverables D9 (GEOMAR, month 12): Report on the setup of coupled model and hindcasts conducted with initial conditions corresponding to ARGO-like sampling. (In progress, only presenting the model setup, ready by 14/10, MojibLatif & Fritz Krüger) D 26 (GEOMAR, month 24): Report on hindcasts conducted with initial conditions extended to include ”RAPID”, and on the feasibility of decadal forecasts with the current ocean observing system (planned for 2014, MojibLatif & Fritz Krüger) D 39 (GEOMAR, month 36): Report on hindcasts conducted with satellite information D 58 (GEOMAR, month 44): Report on the identifications of potential needs that are not captured by the present ocean observing system for enhancing decadal predictions. Steffen M Olsen, Polar Oceanography, DMI, Copenhagen DK

5. Trieste, 1-2 October 2013 NACLIM Core Theme 3: WP 3.1 activities first year • Designed and performed experiments to detect the influence of data resolution in different regions of ocean for climate predictions. (GEOMAR, D32.9). Is Argo type sampling sufficient? • Control run with present day CO2 concentration, KCM (Kiel climate model) using Echam5 (T42L19) and Nemo (Orca2L31) • Ensemble (10) runs starting all 1.1. every 20 years; • Changing temperature and salinity of restart data of control run by doing an artificial coarsening of restart data: leave only certain amount of initial data and fill missing values. • The strategy for filling ‘missing’ data has shown important for the characteristics of the initial field. Problems encountered includes the lack of smoothness and biases. An associated model ‘chock’ is observed. • In the predictions, the strategy has been shown not to be crucial. However, the error is saturated within app. a year or less considering SST. Steffen M Olsen, Polar Oceanography, DMI, Copenhagen DK

6. Trieste, 1-2 October 2013 NACLIM Core Theme 3: WP 3.1 plans • Improve the experimental design • Get rid of the “initial shock” in the model • Consider restoring for one to a few months • Sensitivity to data coverage • Conduct experiments to address the sensitivity of missing layers (Argo coverage) • Conduct experiments to study the regional sensitivity • Plan experiments for D31.26 (months 24) including RAPID data (fluxes?) Steffen M Olsen, Polar Oceanography, DMI, Copenhagen DK

7. Trieste, 1-2 October 2013 NACLIM Core Theme 3: WP 3.2 • Objectives • To address in detail the Arctic region of sparse data coverage • Establish the impact of Arctic data and initialization of the Arctic region on forecast skill • Explore the potential to constrain the state of the Arctic Ocean using the transport monitoring system at the GSR. WP 3.2 Impact of Arctic initialization on forecast skill • Methodology • Model assessment, arctic sector, GSR, processes limiting the skill • Improving model skill (initial conditions) by parameter optimization using climate observations over the Arctic sector. • Perfect-model approach to potential predictability, data withholding • Improve data availability by constructing an Arctic Surface Temperature dataset Steffen M Olsen, Polar Oceanography, DMI, Copenhagen DK

8. Trieste, 1-2 October 2013 NACLIM Core Theme 3: WP 3.2 Deliverables D10 (DMI, month 12): Assessment of model build-up, storage and release of Arctic Ocean freshwater pools. Done (Steffen Olsen) D27 (UHAM, month 24): Report on the documentation and description of improved model parameters. In progress (Armin Köhl) D28 (DMI, month 24): Report on the documentation and description of the new Arctic Ocean dataset combining SST and IST. In progress (GormDybkjær) D40 (DMI, month 36): Report on the establishment of impact of the Arctic region initialization, and on the sources of predictive skill from data withholding experiments. D51 (DMI, month 44): Assessment of the value of the GSR flux monitoring time series for confining the initial state of the upper Arctic Ocean. Initiated Steffen M Olsen, Polar Oceanography, DMI, Copenhagen DK

9. Trieste, 1-2 October 2013 NACLIM Core Theme 3: WP 3.2 activities first year • Assessed the ability of EC-Earth in building up, sustaining and releasing realistically Arctic Ocean freshwater pools (D32.10): • Strong decadal to multi-decadal variability in arctic storage • Explained by ocean ‘filtering’ of largely uncorrelated variability in multiple exchange systems including sea-ice export • Control on sub-polar dynamics including AMOC variability limited to phases of accumulation of freshwater in the Arctic. • Initiated work to assessed the realism of exchanges with the Arctic Mediterranean in EC-Earth (CMIP5 type ocean models), joint with CT2 (linked to D32.51) • Identified inadequate model representation of the two-way exchange system on the Iceland-Faroe Ridge (Task 3.2.1) • Potential consequences for model variability and sensitivity Steffen M Olsen, Polar Oceanography, DMI, Copenhagen DK

10. Trieste, 1-2 October 2013 NACLIM Core Theme 3: WP 3.2 activities first year • Developed and prepared the processing of an Arctic Surface Temperature dataset (D32.28) • Dataset from 1989 onwards ready by march 2014 • Using the atmospheric component of CESAM and its adjoint, new techniques have been applied in order to optimize model parameters (relates to D32.27, months 24) • Some improvement (error reduced up to 20%) is obtained relative to ‘hand-tuned’ model results. Steffen M Olsen, Polar Oceanography, DMI, Copenhagen DK

11. Trieste, 1-2 October 2013 NACLIM Core Theme 3: WP 3.2 plans Processing of the Arctic Surface Temperature Dataset Investigate methods to reduce biases and errors Consider reduced subsets based on user requirements (weakly mean, night-time data) Include uncertainties (model validation and assimilation) Establish the impact of initialization of the Arctic region and identify the sources of predictive skill from data withholding experiments. Revise and detail the experimental design taking into account results of the assessment D32.10 (months 36). A new control run with present day CO2 is considered. Apply the SPSA method for parameter optimization also in the context of ocean initialization Papers in progress linked to the model assessment: Variability of the Arctic Ocean freshwater storage in a coupled climate model. Olsen, Schmith, Yang and Aakjær. Simulating the exchanges across the Iceland-Faroe Ridge in global models by Olsen, Hansen, Østerhus, Quadfasel, Valdimarsson et al. Steffen M Olsen, Polar Oceanography, DMI, Copenhagen DK

12. Trieste, 1-2 October 2013 NACLIM Core Theme 3: Discussion • Joint mid-year workshop CT1&3 on specific topics: • Sup-polar gyre, control on heat transport • Open invitation (CT2). • Broader cooperation with CT2 on verification of transport variability • Data management • Planned publications related to CT3 • Cooperation with upcoming projects: • ICE-Arc (Ice Climate and Economics in the Arctic, FP7 2014-2018, Jeremy Wilkinson, Cambridge). NACLIM poster/presentation at the kick-off? Steffen M Olsen, Polar Oceanography, DMI, Copenhagen DK

13. Trieste, 1-2 October 2013 End Steffen M Olsen, Polar Oceanography, DMI, Copenhagen DK

14. The research leading to these results has received funding from the European Union 7th Framework Programme (FP7 2007-2013), under grant agreement n.308299 NACLIM www.naclim.eu