Vladimir Ryabinin WCRP James Hansen (NASA/GSFC GISS) “Polar Initiative”

History Talk by SPARC at JSC-29 in Arcachon 2008 demonstrating large model errors in polar regions related to treatment of stratosphere in climate models Fast and/or significant changes in the both polar regions noted Coupling stratosphere + ozone with cryosphere Demonstration of the need to use well resolved stratosphere + importance of interactions between various components of the climate system Decision to hold a workshop in 2010 Further consideration and approval at the SPARC SSG-16 in Toronto in Nov 2008 and CliC SSG-5 in Geneva in Dec 2008

Focus Original intention/focus: Why are the poles so different and what is common between them? Why are they so sensitive to GHG increase? This focus is not too new: there have been ACSYS, CliC, IASC, SCAR, IPY, various national programmes, recent events Discussion between SPARC, JPS, and some others: Focus on interaction of polar regions with lower latitudes, processes that affect the poles, interactions between various components of the climate system in the polar regions, oscillations and involved feedbacks that 1) shape the climate change in the polar regions, 2) in understood, observed and modelled well, could contribute to predictability on seasonal, inter-annual, decadal, and centennial scales. Addition to usual identical twins experiments (like CHFP)

SEARCH Sea-Ice Outlook 12 Sep, NSIDC Consistent underestimate of sea-ice extent in the predictions made in August 2009 for September 2009 shows the important role of background meteorological and oceanographic predictions E

WCRP CMIP3: simulated ice extent at mid 21st century relative to (C. Bitz, in press) April

Decadal

Johannessen et al Temperature anomalies

Four leading EOFs of the wintertime (NDJFMA) SAT variability (40N-80N) for Correlation with atmospheric circulation indices PC1 NAO (0.60), AO (0.77) PC2 PNA (-0.48), SLP PC2 (-0.57) PC3 Arctic SAT (0.79) PC4 SCA (0.33) EOF1 and EOF3 explain 94% of the SAT variability north of 60 o N Semenov and Bengtsson (2003)

Coupled model simulation: Arctic sea ice – temperature link Wintertime Arctic SAT and sea ice area Correlation between wintertime Arctic sea ice area and SATs cor (Ice,SAT) = (wintertime) dT/dIce = 1.70 o C/M km 2 (wintertime) Bengtsson, 2004

Coupled model simulation: Barents Sea inflow Annual mean Arctic sea ice area anomalies and oceanic volume flux (upper 125 m) through Spitzbergen-Norway meridional (about 20E) cross-section r = Bengtsson, 2004

Decadal

Some opportunities (in rough terms) Revolution in ocean in-situ observations and their assimilation offering a possibility to initialise the ocean in climate models. Demonstrated impact of the stratosphere on climate. Advances in atmospheric chemistry research. IPY data and possibility of an IPD. Additional predictability associated with warming trends in the climate system and ozone changes. Demonstrated sensitivity of climate models to lower boundary conditions, over the oceans and land. First successful examples showing feasibility of a decadal prediction Need to exchange thoughts and information between various WCRP communities on polar predictability.

First Call Letter to ~ 100 people of two sorts: experts in the above areas + relevant WCRP chairs, asking for ideas on a) processes/feedbacks which are important but less understood and poorly represented in models b) people who know them best and can best review the subject for Centennial time scale Seasonal and decadal time scales c) Ideas how to organize the discussion at the workshop to achieve maximal output and efficiency Fair level of response but with some good ideas.

Methodological issue Instead of addressing gaps in knowledge of polar processes and teleconnections, some respondents embarked on expressing a need for more observations and model improvement. Despite specific recommendations on how to do that may be one of the outcomes of this workshop, the route to them goes through identification of unknown predictable features of the polar climate, so first we would wish to establish what we know about them, what one may expect as predictable feature based on what he or she learnt at the workshop. Nevertheless, many respondent gave excellent suggestions, exactly as requested and expected…

Focus Judah Cohen – snow cover anomalies - modulation of Rossby waves - severity of NH winters. Andrey Prochutinsky, cycles in the Arctic Ocean, propagation of beta-refracted waves in the ocean thermocline. Julie Arblaster - Solar cycle factors acting through UV - ozone – differential heating – amplifying waves modulating forcing – impact of tropospheric circulation – poleward shift of tropical precipitation + direct heating and advection of moisture to precipitation centres leading to strengthening of Hadley and Walker cells – Several: Ozone anomalies and Surface climate in SH Several: Ozone recovery + sea-ice variations

Response Stratosphere – Judah Cohen, Mark Baldwin, Andrew Klekociuk, Julie Arblaster, Adam Scaife Troposphere – Annette Rinke, Ralf Dörsher, Jim Overland Chemical issues – Cecila Bitz, some others Cryo – Cecilia Bitz, Hugues Goosse, Thierry Fichefet, David Holland Oceanic – Andrey Proshutinsky, Hugues Goosse, Thierry Fichefet, Vladimir Ivchenko, Vladimir Zalesny, Igor Polyakov Solar – Kuni Kodera Hydrology – no response 58 people suggested, many new to our community Very weak response from Scandinavia, the region of huge expertise in this subject, which we really wished to engage. Weak response from WCRP project leads!

Proposed way forward Agree on the renewed focus on predictability, as this is a WCRP workshop Approach best respondents and invite them to the Scientific Organizing Committee (SOC) Form SOC Reach out to insufficiently covered areas, write to peple who were proposed as sources of expertise Issue another call Define venue and date (2 nd half 2010), establish a website Engage in the work with SOC on how to get best contributors and extract most useful input from expertise in the many relevant areas of knowledge and research

Proposed SOC Chair: Ted Shepherd (SPARC) Members: Judah Cohen – cryosphere - troposphere Dennis Lettenmaier – polar hydrological feedbacks, GEWEX David Bromwich, CliC Tierry Fichefet – cryospheric links, sea ice and ocean Cecilia Bitz – sea ice Ravishankara – chemistry Andrey Proshutinsky – Arctic Ocean processes Julie Arblaster – solar, troposphere Vladimir Kattsov, JSC Ellie Farahani (secretariat) VR (secretariat)