Transcript Quick - why an ARCSS Arctic System Synthesis?

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 science
2) 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
THC
The Arctic System
today
+
-
Sea ice
(5-3)
+
(3-3)
Permafrost
(2-3)
+
+
- -
-
P-E
+
(6-2)
-
+
- +
-
+
Terrest.
Biomass
-
(2-3)
-
+
+
Terrest.
ice
(3-2)
+
+
weak
strong
(in – out)
Marine
Primary
Prod.
Population
(0-3)
+
+
Econ.
Product.
(1-4)
(1-2)
The Arctic System…
in a few centuries???
THC
(3-3)
+
Atmospheric
Carbon
-
P-E
+
(6-2)
Terrest.
Biomass
-
(2-3)
+
Marine
Primary
Prod.
Sea Level
Rise
(1-2)
+
Population
weak
strong
(in – out)
(0-3)
+
Simulated Climate
Change: next 130 yrs.
NCAR CCSM coupled
atmosphere-ocean
simulation
(Jonathan Overpeck, Bette OttoBleisner and Jeff Kiehl; In prep.)
3xCO2
2100 AD
4xCO2
4xCO2
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
Camp Century
• How do we know?
- ice cores, or
lack thereof
- raised shorelines and
coral reefs around
the world (indicating
up to 6m sea level
rise)
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., fire,
logging, agriculture or climate warming)
Given a positive surface energy balance
Wetter
Seasonally frozen soil
Talik
Dryer
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 icefree 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 icefree 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 icefree 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
Arctic
infrastructure
Biodiversity
Global climate change - possibly abrupt
Release of stored carbon to atmosphere
Sea level rise - possibly abrupt
Global
Lack of predictability for all stakeholders
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