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…

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: 1) determine the value of synthesis to arctic

environmental science2) begin uncovering the best way to carry out arctic

system synthesis

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 “Ah ha“ factor

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

Sea ice(5-3)

P-E(6-2)

Population(0-3)

Econ.Product.

(1-4)

MarinePrimary

Prod.(1-2)

THC(3-3) Permafrost

(2-3)

Terrest. ice(3-2)

Terrest.Biomass

(2-3)

+

+--

-

- -

+

++

+ -

++

++

+

-

+

--

+

+-

(in – out)

weakstrong

The Arctic Systemtoday

P-E(6-2)

Population(0-3)

Econ.Product.

(1-4)

MarinePrimary

Prod.(1-2)

THC(3-3)

Terrest.Biomass

(2-3)

++

+ -

+

-+

(in – out)

weakstrong

The Arctic System…in a few centuries???

AtmosphericCarbon

Sea LevelRise

4xCO23xCO2

2100 AD

4xCO2

2130 AD

NCAR CCSM coupled atmosphere-ocean simulation(Jonathan Overpeck, Bette Otto-Bleisner and Jeff Kiehl; In prep.)

Simulated Climate Change: next 130 yrs.

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

The Last Interglacial

The last time the Arctic warmed above modern…

Ice model fig from: K. Cuffey and S. Marshall, Nature 404, 2000

Greenland130kyrs ago

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

Dye 3

Summit

Summer (JJA) surface air temperature anomalies - 130ka versus the future

Last Interglacial

3xCO2

2100 AD

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

Wetter

DryerTalikPermafrost

Seasonally frozen soil

Time

Permafrost Response to Disturbance (e.g., fire, logging, agriculture or climate warming) Given a positive surface energy balance

(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

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 System Synthesis… selected impacts

Arctic

Global

“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”

Arctic System Synthesis - conclusion

Despite fact that much remains to be done

+6 meters

So, who cares about the arctic anyhow?

Is there a point of no return? If so, when?