The Arctic on the Fast Trackof ChangeJulienne Stroeve
Climate change in the Arctic: A Bellwether for thePlanetBellwether (1) - One that serves as aleader or as a leading indicator offuture trendsBellwether (2) - Sheep that leads theherd often wearing a bellInuksuk - a stone landmark used asa milestone or directional marker
Amplified Arctic warming 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
Signs of warmer Arctic: IncreasingGreenland melt2007 Melting Day Anomalies Melting Index Time Series Courtesy M. Tedesco
Speed-up of many of Greenland’s outletglaciers Jacobshavn Glacier retreat: The rapidly• Current mass loss for retreating Jakobshavn Glacier in Greenland is equally split western Greenland drains the central between surface melt/runoff ice sheet 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). 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 warmingclimate McCall Glacier 1958 2003 Muir Glacier 1941 2004 Glacier image archive available from NSIDC
Average mass balance of a few Arcticglaciers Arctic period 1 y = -6.7749 + 0.0033902x R= 0.23585 Arctic period 2 y = 43.522 - 0.02189x R= 0.81179 0.1 0 -0.1 Recent decades show less variability and -0.2 consistent negative trends. -0.3 -0.4 -0.5 1960 1970 1980 1990 2000 2010 Year Mass balance of Arctic glaciers show shift towards acceleration mass loss from 1988 (mass balance is in m of water equivalent)
Permafrost degradation Permafrost regions occupy 24% of the Siberia Northern Hemisphere and occur as far north as 84oN and as far south as 26oN in the Himalayas.
Increases in permafrost temperatureAlaskan permafrost temperatures, 20 m deep temperatures in the active layer Soil and upper permafrost Russian Permafrost Temperature 4 0.2 m; Trend = 0.78°C/decade 3 0.4 m; Trend = 0.79°C/decade 0.8 m; Trend = 0.65°C/decade 2 1.6 m; Trend = 0.55°C/decade Temperature Departure (°C) 3.2 m; Trend = 0.66°C/decade 1 0 -1 -2 -3 -4 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 Year • 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 Courtesy T. Zhang
Infrastructure impacts Chersky, Russia Alaska Alaska Qinghai-Xizang Highway bridge collapse Courtesy T. Zhang
Methane releasing from lakes Methane bubbles trapped in lake ice Lake bubbling with methane in the ArcticBurning methane over athermokarst lake in Siberia (K.Walter) 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
Poster child of climate change: Arctic sea ice• Frozen surface of the ocean – Pancake Ice 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 rise Multiyear Ice Ridged Ice NOAA Ice Floes
Just to be clear, sea ice is noticebergs! Courtesy Sebastian Copeland
Annual sea ice variability February Siberia Siberia Greenland Greenland Septemb erMaximum extent occurs in February/March (14-16 millionkm2 or 5-6 million square miles) , minimum extent occursin September (7-8 million km2 or about 3 million squaremiles)
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)
September 2007: A new recordminimum Alaska Stroeve et al. 2008
What caused the ice cover to drop in2007? • Unusual atmospheric circulation pattern that promoted warm temperatures and strong winds. June and July Sea Ice MotionTemperature Anomaly Strong ice drift away from A very Warm Arctic Siberian coast across the Arctic
What caused the ice cover to drop in2007? • Big culprit was a thin ice pack. Image courtesy of R. Kwok
Some recovery since 2007, but still indecline 1979-2000 2007 2008 2009Variability points to importance of summer circulation influence
Large changes in the distribution of iceage• 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 Only 320,000 km2 of ice 5+ years March Ice Age Distribution (Week 11) 8 7 6 Extent (million sq-km) 5 4 3 2 5+ winter extent 4 winter extent 3 winter extent 1 2 winter extent 1 winter extent 0 Year
Less than 60,000 km2 of 5+ ice left in September2010 End of Summer Ice Age Distribution 8 7 6 Extent (million sq-km) 5 4 3 2 1 0 Year • Less than 15% of the remaining ice is more than 2 years old, compared to 50-60% during the 1980s
Arctic sea routes opening upNW Passage opening up (2007-2010) NSR also open (2008-2010) Conditions in 2007 Conditions in 2008
Continued sea ice loss inevitable• Seasonally ice free Arctic sooner than we expect? Updated from Stroeve et al., 2007
Models suggest ice-free conditions may occurquickly• 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]. September Sea Ice Extent 10 9 Model drop 1.8 million sq km, 2024–2025 8 Observed drop Ice Extent (million sq-km) 7 1.6 million sq km, 2006–2007 6 5 4 3 CCSM3 model 2 simulation Observations 1 0 1900 1920 1940 1960 1980 2000 2020 2040 2060 2080 2100
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)
Today’s Arctic marine use Hard Minerals Maritime Tourism Major Fisheries Zinc & Coal Oil and Gas Summer Sea Lift Exploration/ScienceIn 2004 there were ~5500 ships Nickel & Copper High grade Iron Ore Snapshot of Summer 2004 Traffic ~ 5475 Ships
Distribution of known resourcesUSGS estimated in 2008 that 90 billion barrels of oil,1,700 trillion cubic feet of natural gas and 44 billionbarrels 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 fortravel and hunting, their main livelihood and basis for theircultural identityPhoto 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
Climate impacts for the rest of us Ice albedo feedback: ice edge retreat Sea ice in spring
Ice-Albedo Feedback-Amplifier of ClimateChange 1.0 Snow 0.8 Ice albedo feedback: 0.6 85% Albedo 0.4 7% 0.2 Ocean 0.0 Largest albedo to smallest
Arctic Amplification has already emerged Alaska Autumn (SON) air temperature anomalies: 2004- 2008 minus 1979- 2008 Updated from Serreze et al., 2008
Impact of sea ice loss on landtemperaturesPermafrost contains about 1672 Gt of carbon. Forcomparison, carbon content of Earth’s atmosphere: ~730 Gt today. Courtesy D. Lawrence
Results: Strength of the PCFCumulative NEE (Gt C) PCF Start 2023±4 Date (year) 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• Many components of the Arctic environment are undergoing large changes.• Land and ocean ice loss in the Arctic is consistent with model simulations made with observed records of GHGs.• Sea ice loss is outpacing climate model projections, ice free summers by 2050?• Sea ice loss is already affecting the environmental, biological and societal systems in• the Arctic. ice loss will likely have significant Continued impacts beyond the Arctic.
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