Arctic System Synthesis: Is the Arctic Headed Toward a New State? Jonathan Overpeck, ARCSS Committee*, ARCSS Synthesis retreat participants* * See abstract for the names and affiliations…

• The synthesis was initiated in 2003 by the ARCSS Committee Quick - why an ARCSS Arctic System Synthesis? • The synthesis was initiated in 2003 by the ARCSS Committee • The synthesis was designed to be non-programmatic, and is viewed as an experiment to: determine the value of synthesis to arctic environmental science begin uncovering the best way to carry out arctic system synthesis The “Ah ha“ factor 3) identify key arctic system unknowns (e.g., for the new ARCSS Science Plan, due next year) 4) learn something new about how the arctic system works, and what it means for the future

The 2003-04 ARCSS Arctic System Synthesis • An adaptive process - the participants guided both the goals and the process (and soon, the final products…)

The 2003-04 ARCSS Arctic System Synthesis • An adaptive process - the participants guided both the goals and the process (and soon, the final products…) • Quickly converged on the value of “the big question,” which focused several days of plenary and breakout group discussions… “Is the Arctic System moving to a new state outside the envelop of the natural glacial-interglacial cycle?”

Includes the biosphere and humans too! Cartoon drafted by E. Carmack

The Arctic System today + - Sea ice THC Permafrost P-E Biomass (5-3) P-E (6-2) Population (0-3) Econ. Product. (1-4) Marine Primary Prod. (1-2) THC (3-3) Permafrost (2-3) Terrest. ice (3-2) Biomass + - Blue components affect other components more than they are affected, whereas yellow impacted more than they impact. (in – out) weak strong

The Arctic System… in a few centuries??? + - + - + + + THC Atmospheric (3-3) Atmospheric Carbon + - P-E (6-2) Terrest. Biomass (2-3) + - + Marine Primary Prod. (1-2) Sea Level Rise Econ. Product. (1-4) + Population (0-3) + weak strong (in – out)

Simulated Climate Change: next 130 yrs. NCAR CCSM coupled atmosphere-ocean simulation (Jonathan Overpeck, Bette Otto-Bleisner and Jeff Kiehl; In prep.) 4xCO2 3xCO2 2100 AD 2130 AD

What happened the last time the arctic warmed above 20th century levels?? The Last Interglacial

The last time the Arctic warmed above modern… Much (up to 3/4ths) of the Greenland Ice Sheet melted • How do we know? - ice cores, or lack thereof - raised shorelines and coral reefs around the world (indicating up to 6m sea level rise) Camp Century Summit Dye 3 Greenland 130kyrs ago Ice model fig from: K. Cuffey and S. Marshall, Nature 404, 2000

Summer (JJA) surface air temperature anomalies - 130ka versus the future 3xCO2 2100 AD Last Interglacial 4xCO2 2130 AD

Current Greenland Summer Melt 2002 all-time record melt area Melting up to an elevation of 2000 m 16% increase from 1979 to 2002 130,000 years ago, Greenland may have melted by 2/3rds in 500 years or less

Is the current summer-time Arctic sea ice area retreat a sign of things to come too? • Downward trend in ice extent ~ 3 % per decade • Size of Colorado and New Hampshire (National Snow and Ice Data Center, University of Colorado, Boulder)

Permafrost Last 50 years has seen large warming of permafrost in many parts of the Arctic Photo credits: Larry Hinzman

Permafrost Response to Disturbance (e. g Permafrost Response to Disturbance (e.g., fire, logging, agriculture or climate warming) Given a positive surface energy balance Wetter Dryer Seasonally frozen soil Talik Permafrost Time (Larry Hinzman, et al. 2003; and unpublished)

Arctic System Synthesis… the Ah ha’s • arctic IS likely being driven to a new seasonally ice-free state • current patterns of system change are likely a sign of things to come • feedbacks generally positive in Arctic; cloud feedback are not likely to prevent state change These guys just didn’t wait long enough…

Arctic System Synthesis… the Ah ha’s • arctic IS likely being driven to a new seasonally ice-free state • current patterns of system change are likely a sign of things to come • feedbacks generally positive in Arctic; cloud feedback are not likely to prevent state change • must therefore look outside arctic for possible thermostats - e.g., decreased poleward heat transport by atmosphere and/or oceans

Arctic System Synthesis… the Ah ha’s • arctic IS likely being driven to a new seasonally ice-free state • current patterns of system change are likely a sign of things to come • feedbacks generally positive in Arctic; cloud feedback are not likely to prevent state change • must therefore look outside arctic for possible thermostats - e.g., decreased poleward heat transport by atmosphere and/or oceans • change likely to accelerate across poorly understood thresholds

Arctic System Synthesis… selected impacts Northern lives/lifestyles/culture Costs to both existing and future infrastructure Biodiversity Global climate change - possibly abrupt Release of stored carbon to atmosphere Sea level rise - possibly abrupt Lack of predictability for all stakeholders Arctic IPCC95 best estimates 1-3.5 by 2100 Volcanoes - all the news is not bad news... Global

Arctic System Synthesis - conclusion “Our analysis of current trends, models, and feedback mechanisms leads us to state--with 80/20 confidence--that the arctic system is moving toward a new state outside known cycles, and that this change will impact the Earth system” Despite fact that much remains to be done

So, who cares about the arctic anyhow? Is there a point of no return? If so, when? +6 meters