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Julienne Stroeve's lecture at the Longmont Public Library
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The Arctic on the Fast Track of Change
Julienne Stroeve
Climate change in the Arctic: A Bellwether for the Planet
Bellwether (1) - One that serves as a leader or as a leading indicator of future trends
Bellwether (2) - Sheep that leads the herd often wearing a bell
Inuksuk - a stone landmark used as a milestone or directional marker
Air Temperature: A1B Scenario by 2100
Global mean warming of ~2.8oC (or ~5F);Much of land area warms by ~3.5oC (or ~6.3F)
Arctic warms by ~7oC (or ~12.6F)
IPCC-AR4 ensemble mean, A1B Scenario, courtesy M. Holland
Amplified Arctic warming
Signs of warmer Arctic: Increasing Greenland melt
2007 Melting Day Anomalies
Melting Index Time Series
Courtesy M. Tedesco
Speed-up of many of Greenland’s outlet glaciers
• Current mass loss for Greenland is equally split between surface melt/runoff and ice discharge across calving fronts.
• Future prediction of Greenland’s contribution to sea level rise is difficult because it is unclear how these outlet glaciers will respond.
• Melting of Greenland would produce 7.2 m sea level rise (or about 24 ft).
Jacobshavn Glacier retreat: The rapidly retreating Jakobshavn Glacier in
western Greenland drains the central
ice sheet
Image courtesy NASA Earth Observatory, Cindy Starr, based on data from Ole Bennike and Anker Weidick (Geological Survey of Denmark and Greenland) and Landsat data.
Glacier Fluctuations: clear indicators of a warming climate
1958 2003
McCall Glacier
1941 2004
Muir Glacier
Glacier image archive available from NSIDC
Average mass balance of a few Arctic glaciers
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
1960 1970 1980 1990 2000 2010
Arctic period 1Arctic period 2
y = -6.7749 + 0.0033902x R= 0.23585
y = 43.522 - 0.02189x R= 0.81179
Year
Mass balance of Arctic glaciers show shift towards acceleration mass loss from 1988 (mass balance is in m of water equivalent)
Recent decades show less variability and consistent negative trends.
Permafrost degradation
Permafrost regions occupy 24% of the Northern Hemisphere and occur as far north as 84oN and as far south as 26oN in the Himalayas.
Greenland
SiberiaAlaska
Increases in permafrost temperature
• Alaska: 4 to 6oC increase in 20th Century, 2 to 3oC in last 30 years
• Siberia: >3oC increase from mid-1950s to 1990
• Canadian Arctic: 1 to 3oC increase in past several decades
• Tibetan Plateau: up to 1.0oC increase since 1970s
Russian Permafrost Temperature
-4
-3
-2
-1
0
1
2
3
4
1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000
Year
Te
mp
era
ture
De
par
ture
(°C
)
0.2 m; Trend = 0.78°C/decade
0.4 m; Trend = 0.79°C/decade
0.8 m; Trend = 0.65°C/decade
1.6 m; Trend = 0.55°C/decade
3.2 m; Trend = 0.66°C/decade
Alaskan permafrost temperatures, 20 m deep Soil temperatures in the active layer and upper permafrost
Courtesy T. Zhang
Infrastructure impactsChersky, Russia
Qinghai-Xizang Highway bridge collapse
Alaska
Alaska
Courtesy T. Zhang
Methane releasing from lakes
Burning methane over a thermokarst lake in Siberia (K. Walter)
Methane bubbles trapped in lake ice
Lake bubbling with methane in the Arctic
Courtesy K. Walter
“Greening” of the Arctic
Trends in vegetation synthetic activity from 1982–2005 (GIMMS-G AVHRR Vegetation indices)
Significant positive trends
Significant negative trends
Courtesy S. Goetz, Woods Hole
Greenland
Poster child of climate change: Arctic sea ice• Frozen surface of the ocean –
originates within ocean Does not include land ice
(glaciers, ice sheets) Does not include other floating
ice (ice shelves, icebergs) If sea ice melts, sea level will not
riseNOAA
Pancake Ice
Ridged IceIce Floes
Multiyear Ice
Just to be clear, sea ice is not icebergs!
Courtesy Sebastian Copeland
Annual sea ice variability
Maximum extent occurs in February/March (14-16 million km2
or 5-6 million square miles) , minimum extent occurs in September (7-8 million km2 or about 3 million square miles)
February
September
Gre
en
lan
d
Gre
en
lan
d
Siberia Siberia
Alaska
Alaska
Recent changes in Arctic sea ice• Previous studies have indicated a decline in annual Arctic sea ice cover since
the late 1970s at a rate of -3%/decade or a loss in ice area of nearly 300,000 sq-km [e.g. Parkinson et al., 1999; Cavalieri et al., 1997; Bjorgo et al., 1997].
Current trend since 1979 is now at -4.3 % per decade
Losing the summer sea ice cover
Time-series of September ice concentration during the modern satellite data record (1979 to 2010)
Stroeve et al. 2008
September 2007: A new record minimum
Alaska
Sib
eria
Greenland
What caused the ice cover to drop in 2007?• Unusual atmospheric circulation pattern that promoted
warm temperatures and strong winds.
A very Warm ArcticStrong ice drift away from Siberian coast across the Arctic
Sea Ice MotionJune and July Temperature Anomaly
What caused the ice cover to drop in 2007?
• Big culprit was a thin ice pack.
Image courtesy of R. Kwok
Some recovery since 2007, but still in decline
1979-2000
2009
20072008
Variability points to importance of summer circulation influence
Large changes in the distribution of ice age
• Unfortunately we don’t have long-term records of Arctic-wide ice thickness measurements.
• Tracking the age of the sea ice is one means to look a past thickness distribution, since older ice tends to be thicker.
Spring 1986 Spring 1990 Spring 2007
Maslanik et al., 2007
Very little old ice left
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
0
1
2
3
4
5
6
7
8
March Ice Age Distribution (Week 11)
5+ winter extent4 winter extent3 winter extent2 winter extent1 winter extent
Year
Ex
ten
t (m
illio
n s
q-k
m)
Only 320,000 km2 of ice 5+ years
Less than 60,000 km2 of 5+ ice left in September 2010
• Less than 15% of the remaining ice is more than 2 years old, compared to 50-60% during the 1980s
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
0
1
2
3
4
5
6
7
8End of Summer Ice Age Distribution
Year
Ext
ent
(mil
lio
n s
q-k
m)
Arctic sea routes opening up
NW Passage opening up (2007-2010)
Conditions in 2007
NSR also open (2008-2010)
Conditions in 2008
Peering into the Future
Continued sea ice loss inevitable• Seasonally ice free Arctic sooner than we expect?
Updated from Stroeve et al., 2007
1900 1920 1940 1960 1980 2000 2020 2040 2060 2080 21000
1
2
3
4
5
6
7
8
9
10September Sea Ice Extent
Ice
Ext
ent
(mill
ion
sq
-km
)
Models suggest ice-free conditions may occur quickly
• Climate models suggest once the sea ice cover is thinned sufficiently, a strong “kick” from natural variability can initiate a rapid slide towards ice-free conditions in summer [e.g. Holland et al., 2006].
CCSM3 model simulationObservations
Model drop1.8 million sq km, 2024–2025
Observed drop1.6 million sq km, 2006–2007
The set up looks right
• Mean thickness (70-90N) in CCSM3 before abrupt change: 1.71 m
• Mean thickness (70-90N) from ICESat in Spring 2007: 1.75 m (data from D. Yi and J. Zwally)
Increased Access to the Arctic
Zinc & Coal
Today’s Arctic marine use
Snapshot of Summer 2004
Traffic ~ 5475 Ships
Hard Minerals
Nickel & Copper
High grade Iron Ore
Maritime Tourism
Major Fisheries
Oil and GasSummer Sea LiftExploration/Science
In 2004 there were ~5500 ships
Distribution of known resourcesUSGS estimated in 2008 that 90 billion barrels of oil, 1,700 trillion cubic feet of natural gas and 44 billion barrels of natural gas liquids may be found in the Arctic, of which ~84% occurs offshore.
Oil Gas
Impact on polar bears and other Arctic species
Polar bears under pressure
• For every week a bear has not been hunting, it is 22 pounds lighter. The bear’s reproductive
system is strongly linked to their fat stores.
• The offshore ice-based ecosystem is sustained by upwelling nutrients that feed the plankton, shrimp, and other small organisms, which feed the fish. These in turn feed the seals, which feed the bears.
Seals also feeling impacts
• Lack of sea ice the last 2 years in the Gulf of St. Lawrence led to loss of thousands of baby harp seals.
• Canada Fisheries reported that on the first day of spring 2010, there were only 600 seals in the gulf, when normally there are 30,000.
Seal image courtesy Sebastian Copeland
Community impactsMany Arctic indigenous communities rely on sea ice for travel and hunting, their main livelihood and basis for their cultural identity
Photo by Craig George
Impacts of changing sea ice on food resources• Reductions in sea ice
are shrinking the marine habitat for ice-dependent seals, walrus, polar bears and some seabirds.
• Sea-ice is thinner and now drifts far away during the summer, taking with it the seals, walrus and polar bears upon which the village’s Inuit residents rely for food.
Courtesy S. Gearheardt
Safety issues• Changes in sea ice -
local and regional thinning, unusual cracks, changes in the timing of break up and freeze up are already having a serious impact on travel safety. Before venturing
onto ice in fall or spring, hunters are encouraged to test its stability with a harpoon.
Courtesy S. Gearheardt
Community locations threatened• Native communities are facing erosion problems and relocation
of communities (at huge costs) as a result. Lack of sea ice cover exposes shoreline to waves and storms.
Photo Craig George
Sea ice in spring
Climate impacts for the rest of us
Ice albedo feedback: ice edge retreat
Ice-Albedo Feedback-Amplifier of Climate Change
Ice albedo feedback:
Largest albedo to smallest
0.0
0.2
0.4
0.6
0.8
1.0
Alb
edo
Snow
Ocean
85%
7%
Autumn (SON) air temperature anomalies: 2004-2008 minus 1979-2008
Updated from Serreze et al., 2008
Arctic Amplification has already emerged
SiberiaG
reen
land
Alaska
Impact of sea ice loss on land temperatures
Permafrost contains about 1672 Gt of carbon. For comparison, carbon content of Earth’s atmosphere: ~730 Gt today.
Courtesy D. Lawrence
Results: Strength of the PCF
PCF Start 2023±4
Date (year)
Cum
ulat
ive
NE
E (
Gt C
)
Paper in Tellus-B
Impacts on precipitation/snow cover• A warmer atmosphere changes atmospheric
circulation and is able to hold more water vapor and thus could lead to more precipitation, especially in autumn and winter.
Courtesy of Rutgers University Climate Lab
Final Statements
• Continued ice loss will likely have significant impacts beyond the Arctic.
• Land and ocean ice loss in the Arctic is consistent with model simulations made with observed records of GHGs.
• Many components of the Arctic environment are undergoing large changes.
• Sea ice loss is already affecting the environmental, biological and societal systems in the Arctic.
• Sea ice loss is outpacing climate model projections, ice free summers by 2050?
Climate Change and Colorado’s Future
•
LearnMoreAboutClimate.Colorado.edu
• New website that localizes climate change for Colorado
• Video series
• Scientists & citizens explain how climate
change is affecting our state
• Educator Resources
• Lesson plans & resources to help bring climate change to the
classroom • Plus resources to help citizens in making green choices