IMPACTS OF A WARMING ARCTIC · IMPACTS OF A WARMING ARCTIC 39 Northward Shifting Treeline ©2004, ACIA/ Map ©Clifford Grabhorn Climate change is projected to cause vegetation shifts

IMPACTS OF A WARMING ARCTIC

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Northward Shifting Treeline

©2004, ACIA/ Map ©Clifford Grabhorn

Climate change is projected tocause vegetation shifts becauserising temperatures favor taller,denser vegetation, and will thuspromote the expansion of forestsinto the arctic tundra, and tundrainto the polar deserts.

Current Arctic Vegetation Projected Vegetation, 2090-2100

Present day natural vegetationof the Arctic and neighboringregions from floristic surveys.

Projected potential vegetation for2090-2100, simulated by the LPJDynamic Vegetation Model drivenby the Hadley2 climate model.

Ice Polar Desert / Semi-desertTundraBoreal ForestTemperate Forest

Ice Polar Desert / Semi-desertTundraBoreal ForestTemperate ForestGrassland

©2004, ACIA/ Maps ©Clifford Grabhorn


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©2004, ACIA/ Map ©Clifford Grabhorn Note: The arrows depicting CO2 and CH4 are not drawn to scale.

The projected reduction in tundra and expansion of forest will cause a decrease in surface reflec-tivity, amplifying global warming because the newly forested areas are darker and more texturedand thus will absorb more solar radiation than the lighter, smoother tundra.

Vegetation Change


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Seasonal Switch from Carbon Sink to Carbon Source

©2004, ACIA


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Changing Landscape Dynamics with Warming

In northern Norway, Sweden, and Finland, many areas of discontinuous permafrost have small hills or mounds with wet depressions, each with characteristicvegetation (left). As climate warms, permafrost thaws and the wet areas increase in extent. The more productive vegetation captures more carbon dioxidebut the greater extent of wet areas leads to greater methane emissions (middle) (this is already being observed). Eventually (right), the permafrost thawscompletely, and the balance between methane emissions and carbon dioxide drawdown depends on subsequent drainage and precipitation.

©2004, ACIA


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This schematic illustrates the projected upslope and northward displacement of vegetation zones in the Arctic as a result offuture warming. Note the difference in altitude of vegetation boundaries on north and south facing slopes. The altitudinal andlatitudinal zones are analogous, but not identical.

©2004, ACIA

Vegetation Zone Shift

North American Forest Distribution andProjected Shifts to Aspen Woodland as Climate Warms

Eurasian Forest Distribution

As climate warms, the boundaries offorest types are expected to shift.Although precipitation is projected toincrease, in some areas the increasewill be insufficient to keep upwith the increased evaporationthat accompanies rising airtemperatures. Thus, someareas will become too dryto support closedcanopy boreal forestand are projected toconvert to a moreopen formation ofaspen woodland,sometimes referredto as “parkland”.These areas areshown in red onthe map, which isderived from amodel scenariounder twice pre-industrial carbondioxide concentra-tions, which couldoccur as early as themiddle of this century.

This map of forest types inEurasia illustrates how climateaffects forest distribution. Inthe colder northern part of theregion, there is a southward displacement of forest types

compared to the western part.As climate warms, some

areas that are currentlysparsely vegetated areexpected to becomemore heavily vegetat-ed, with both positiveand negative conse-quences for theregion and theworld.

Potential future aspen parkland

Forest - TundraLichen WoodlandClosed Forest

Forest - TundraSparse Northern TiagaMiddle and Southern TaigaSparce Forest and Meadow

Current



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Projected


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White Spruce Response to Warming

The graph shows the historic and projected relationshipbetween white spruce growth and summer temperature incentral Alaska. A critical temperature threshold wascrossed in 1950, after which the growth began to fall. Theprojection of the Canadian climate model (CGCM2) sug-gests that this species is likely to be eliminated in theregion by the latter part of this century.

Siberian Larch and Warm Season Temperature

The graph shows the historical relationship between growth ofSiberian larch and warm season temperature and two futurewarming scenarios in Russia’s Taymir Peninsula. These treesrespond positively to temperature increases. The warmer of thetwo scenarios above (ECHAM/OPYC3) would roughly double thegrowth rate and make this marginal site a productive forest. (The “site” is actually an average of four climate stations on theTaymir Peninsula.) The CSM_1.4 scenario would eliminate periodsduring which growth is severely limited by temperature.

©2004, ACIA ©2004, ACIA


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Black Spruce Response to Warming

The graph shows the relationship of summer temperaturesat Fairbanks, Alaska and relative growth of black spruce,historically and for two future warming scenarios.Average summer temperature is an excellent predictor ofblack spruce growth, with warm years resulting in stronglyreduced growth. By 2100, temperatures projected by bothscenarios would not allow the species to survive.

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The graph shows the area of North American boreal forestthat burned each year, in millions of hectares. The averagearea burned has more than doubled since 1970, coincidingwith climatic warming in the region.

Boreal Forest Burned in North America

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Spruce Bark Beetle OutbreaksSouthern Kenai Peninsula

©2004, ACIA

The relationship of the spruce bark bee-tle to climate involves three factors,including two direct controls on insectpopulations and an indirect control ontree resistance. First, two successive coldwinters depress the survival rate of thebark beetle to a level low enough thatthere is little outbreak potential the fol-lowing summer. However, winters havebeen abnormally warm for decades inthe North American Arctic, so the condi-tions for this control have not been metfor some time. Second, the bark beetlenormally requires two years to completeits life cycle, but in abnormally warmsummers, it can complete its life cycle inone year, dramatically increasing thepopulation and the resulting damage.


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The colors indicate the change in the number of days in the growing season from the pres-ent to 2070-2090 under the Hadley 3 climate scenario. An average of three climatemodel's results suggests about a 20-30 day increase in the growing season for areas northof 60˚ latitude. The growing season is defined as the number of consecutive days in whichthe minimum temperature is above 0˚C.

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+60

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+30

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0

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Projected Change in Growing Season Length by 2070-2090Minimum Temperature greater than 0˚C

(days)



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Arctic Marine Food Web

©2004, ACIA

Research in the Beaufort Sea suggests that ice algae at the base of the marine food webmay have already been profoundly affected by warming over the last few decades.


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Past and potential future development of cod andshrimp harvest off Greenland with climate change.

Observed and Projected Harvests

©2004, ACIA

Mixing Waters and Fish Drift Routes

The main water masses in the Iceland-EastGreenland-Jan Mayen areas. The red arrows indicatethe main drift routes of larvae and fish less thanone year old.

©2004, ACIA


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Historic Changes in Migration Routes

Spawning areasJuvenile areasMain feeding areas Spawning migrationsFeeding migrationsSpawning migrations

(d)

(e)

(a)

(b)

(c)©2004, ACIA/ Map ©Clifford Grabhorn

Herring Spawning Stock and Temperature

Norwegian spring spawning herring stocks increased greatlyduring the warming period of the 1920s-1930s and thendeclined rapidly beginning in the late 1950s. Overfishing wasthe primary cause of the collapse of the population, althoughclimatic cooling was probably a contributing factor.

©2004, ACIA

Changes of migration routes (left), and feeding and win-tering areas of Norwegian spring spawning herring duringthe latter half of the 20th century. (a) Normal migrationpattern during the warm period before 1965. (b-c) After apulse of sea ice and freshwater from the Arctic sent cold,low-salinity water into the East Greenland and the EastIcelandic currents, until the stock collapsed in 1968. (d)During years of low stock abundance (1972-1986). (e) Thepresent day migration pattern.


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Eastern Bering Sea Catch, 1954-2000

©2004, ACIA

Western Bering Sea Catch, 1965-2001

©2004, ACIA

In the Bering Sea, rapid climate change is already apparent, and its impacts significant. The Bering Sea is experiencing a major warming inbottom water temperature that is forcing cold-water species of fish and mammals northward and/or into decline. The first concern of BeringSea fisheries management is thus likely to be managing for the ecosystem reorganization that is and will continue to be taking place as aresult of climate change.


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Possible Changes in Fish Distribution

Possible changes in the dis-tribution of selected fishspecies the Norwegian andBarents Seas resulting froman increase in ocean temper-ature of 1 to 2˚C.



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The production of farmed Atlantic salmon and rainbowtrout 1988-2003. The red line is a projection for 2004-2006. The projected decrease reflects problems causedby fish diseases and economic issues. Climate changeadds additional uncertainties.

Possible Changes in Faroe Island Aquaculture Production

©2004, ACIA


Long-distance animal migration routes are sensitiveto climate-related changes such as alterations inhabitat and food availability. The amplification of warming in the Arctic thus has global implications forwildlife.

Knots

GLOBAL

Terns

Whales


REGIONAL LEVEL

Polar BearsTrees and shrubs

Whales

BirdsSalmonReindeer

At the regional level, vegetation and the animals associated with it will shift inresponse to warming, thawing permafrost, and changes in soil moisture andland use. Range shifts will be limited by geographical barriers such as moun-tains and bodies of water. Shifts in plankton, fish, and marine mammals andseabirds, particularly those associated with the retreating ice edge, will resultfrom changes in air and ocean temperatures and winds.


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LANDSCAPE LEVEL

At the landscape level, shifts in the mosaic of soils and related plant and animal communities will be associated with warming-driven drying of shallow ponds, creation of new wet areas, land use change, habitat fragmentation, and pests and diseases.These changes will affect animals' success in reproduction, dispersal, and survival, leading to losses of northern species andrange extensions of southern species.



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Changes in snow conditions, ice layers, the cavity beneaththe snow, summer temperatures, and nutrient cycling acton individual plants, animals, and soil microorganismsleading to changes in populations. It is at the level of theindividual animal and plant where responses to the cli-mate take place leading to vegetation shifts across theearth.

PLOT LEVEL

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Cascading Impacts in a Changing Climate

Population dynamics (number of individuals in a particular area)of Svalbard reindeer and sibling voles on Svalbard, along withobserved (circles) and projected (squares) changes in vegetation.

©2004, ACIA


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Kitikmeot Inuit Observations of Impacts of Warming on Caribou

©2004, ACIA

Climate-induced changes to arctic tundra are projected to cause vegetation zones to shift significantly northward, reducing thearea of tundra and the traditional forage for these herds. Freeze-thaw cycles and freezing rain are also projected to increase.These changes will have significant implications for the ability of caribou and reindeer populations to find food and raise calves.Future climate change could thus mean a potential decline in caribou and reindeer populations, threatening human nutrition formany indigenous households and a whole way of life for some arctic communities.


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Caribou Ranges and Indigenous Peoples of North America

Sub-species


This chart (right) apportions annual averageharvest of the Porcupine Caribou Herd innorthwestern Canada and northeastern Alaskaby user group. Approximately 89% of the har-vest is taken in Canada, and more than 90% ofthe total harvest is taken by indigenous com-munities.

Harvest of Porcupine Caribou Herd by User Group

©2004, ACIA


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Potential Climate Change Impacts on the Porcupine Caribou Herd

Climate ChangeCondition

Higher plant growthrate

Core calving groundsmove further north

Less use of foothillsfor calving

Higher calf growth rate

Lower predation risk Higher June calf survival

Cows replenish protein reserves faster

Higher probability ofpregnancy

Concern over development onnorthern portion ofpresent core calvingarea

Earlier SnowMelt on Coastal

Plain

Warmer, DrierSummer

Warmer, Wetter Autumn

Warmer, WetterWinter

Warmer Spring

Overall Effect

Earlier peak biomass

More use of coastal zone while in Alaska

More dependence on insect relief areas, especially from mid- to lateJuly

Plants harden earlier

Reduction in mosquito breedingsites

Significant increase in oestrid activity

Greater frequency of fire on winter range

Fewer “mushroom” years

More frequent icingconditions

Deeper denser snow

More freeze / thawdays, snow forms icelayers

Faster spring melt

Calving rangeimproves, summer,autumn and winterranges probably lowerquality

Extremes (such asvery deep snow or very late melt) hard to adapt to

Need to factor climate changeimpacts on harvestlevels

Need to communicateimpacts of climate onharvest patterns andtiming

Need to set up monitoring programs

Seasonal distributionless predictable, timing less pre-dictable

Improved June condi-tion but later summerreduced condition,more rapid weightloss in winter andearly spring

High pregnancy ratesbut overall lower survival and recruitment; Shiftmortality later in year(late winter, spring);Herd more likely todecline

Need to assess habitatprotection in relationto climate trends

Move to windsweptslopes

Accelerated weightloss in spring

Faster spring migration Lower productivity dueto high springmortality

Higher wolf predationdue to use ofwindswept slopes

Concern over timingand location of springmigration in relationto harvest

Later to leave winter range

Increased use of lowsnow regions

Greater over-winterweight loss

Maternal bond broken earlier

Caribou abandonranges with severesurface icing

Unknown Unknown Protection of lowsnow regions

Movement out ofAlaska earlier in season

Increased harassmentresulting in lower bodycondition

Lower probabilityof pregnancy

Protection of insectrelief areas important

Impact on Habitat Impact onMovement

Impact on BodyCondition

Impact onProductivity

ManagementImplications

©2004, ACIA


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Tanana River Ice Break-up Dates

The graph shows the ice break-up dates for the Tanana River atNenana, Alaska over the last 80 years. Though there is consid-erable variability from year to year, there is a trend toward earlier break-up by over a week.

Day of the Year

©2004, ACIA

Freshwater Food Web

©2004, ACIA

Warming is very likely to accelerate rates of contaminant transfer to the Arcticand increased precipitation is very likely to increase the amount of persistentorganic pollutants and mercury that are deposited in the region. Increasingcontaminant levels in arctic lakes will accumulate in fish and other animals,becoming magnified as they are transferred up the food chain.


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Fish Growth Rate and Temperature

These growth curves (in percent per day) for various fishspecies illustrate that growth typically increases with risingtemperature up to a certain point and then declines astemperature continues to rise. Northern species (A. Arcticchar, B. lake cisco, C. lake trout, and D. brook trout - all inblue) are grouped toward the lower temperatures on theleft, and have a more peaked curve, indicating only narrowand typically low temperature ranges over which optimalgrowth is achieved. This suggests that their ability toadapt to a warming climate is likely to be quite limited.The unlabeled growth curves are for various lower latitudespecies.

©2004, ACIA

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IMPACTS OF A WARMING ARCTIC · IMPACTS OF A WARMING ARCTIC 39 Northward Shifting Treeline ©2004, ACIA/ Map ©Clifford Grabhorn Climate change is projected to cause vegetation shifts