Regional Climate Impacts: Alaska
Alaska
L1 R1
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L6 R6
L7 Over the past 50 years, Alaska has warmed at more
Observed and Projected Temperature Rise in Alaska R7
L8 than twice the rate of the rest of the United States. R8
L9 Its annual average temperature has increased 3.4°F, R9
L10 while winters have warmed even more, by 6.3°F1. R10
L11 As a result, climate change impacts are much more R11
L12 pronounced than in other regions of the United R12
L13 States. The higher temperatures are already causing R13
L14 earlier spring snowmelt, reduced sea ice, wide- R14
L15 spread glacier retreat, and permafrost warming1,2. R15
L16 These observed changes are consistent with climate R16
L17 model projections of greater warming over Alaska, R17
L18 especially in winter, as compared to the rest of the R18
L19 country. R19
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L21 Climate models also project increases in precipita- R21
L22 tion over Alaska. Simultaneous increases in evapo- R22
L23 ration due to higher air temperatures, however, are R23
L24 expected to lead to drier conditions overall, with CIMP3-A4 R24
L25 reduced soil moisture3. In the future, therefore, Alaska’s annual average temperature has increased 3.4ºF over the past R25
50 years. The observed increase shown above compares the average
L26 model projections suggest a longer summer grow- R26
temperature of 1993 to 2007 to a 1960s and 1970s baseline, an increase
L27 ing season combined with an increased likelihood of over 2ºF. The brackets on the thermometers represent the likely range R27
L28 of summer drought and wildfires. of model projections, though lower or higher outcomes are possible. By R28
L29 the end of this century, the average temperature is projected to rise by R29
5 to 13ºF above the 1960s and 1970s baseline.
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L32 Fairbanks Frost-free Season R32
L33 150 Average annual temperatures in Alaska are R33
L34 140 projected to rise about 4 to 7°F by the middle R34
L35 130 of this century. How much temperatures rise R35
Number of Frost-free Days
L36 120 later in the century depends strongly on global R36
L37 110 emissions choices, with increases of 5 to 8°F R37
L38 100 projected with lower emissions†, and increases R38
L39 90 of 8 to 13°F with higher emissions†. Higher R39
L40 80 temperatures are expected to continue to R40
L41 # frost-free days
70 reduce Arctic sea ice coverage. Reduced sea R41
L42 60 ice provides opportunities for increased ship- R42
L43 50 ping and resource extraction. At the same time, R43
L44 40 however, it increases coastal erosion, raises R44
L45 30 the risk of accidents as offshore commercial R45
1904 1914 1924 1934 1944 1954 1964 1974 1984 1994 2004
L46 Year activity increases, and is expected to drive R46
University of Alaska5
L47 major shifts of marine species such as pollock R47
L48 Over the past 100 years, the length of the frost-free season in and other commercial fish stocks. R48
Fairbanks, Alaska, has increased by 50 percent. The trend toward
L49 a longer frost-free season is projected to produce benefits in R49
L50 some sectors and detriments in others. R50
2nd Public Review Draft, January 2009 141
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The U.S. Climate Change Science Program Global Climate Change Impacts in the United States
L1 Summers are becoming longer Insect outbreaks and wildfires are R1
L2 and drier. increasing with warming. R2
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L4 Between 1970 and 2000, the snow-free season Climate plays a key role in determining the extent R4
L5 increased by approximately 10 days across Alaska, and severity of insect outbreaks and wildfires9,10. R5
L6 primarily due to earlier snowmelt in the spring6,7. During the 1990s, for example, south-central Alas- R6
L7 A longer growing season has potential economic ka experienced the largest outbreak of spruce bark R7
L8 benefits, providing a longer period of outdoor and beetles in the world9,11. This outbreak occurred be- R8
L9 commercial activity such as tourism. However, cause rising temperatures allowed the spruce bark R9
L10 there are also downsides. For example, white beetle to survive over the winter and to complete R10
L11 spruce forests in Alaska’s interior are experienc- its life cycle in just 1 year instead of the normal 2 R11
L12 ing declining growth due to drought stress8 and years. Healthy trees ordinarily defend themselves R12
L13 continued warming could lead to widespread death by pushing back against burrowing beetles with R13
L14 of trees9. The decreased soil moisture in Alaska their pitch. From 1989 to 1997, however, the region R14
L15 also suggests that agriculture in Alaska might not experienced an extended drought, leaving the trees R15
L16 benefit from the longer snow-free growing season. too stressed to fight off the infestation. R16
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L21 Alaska Spruce Beetle Infestation R21
L22 Kenai Peninsula, 1971 to 1998 R22
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L49 Berman et al.12 R49
L50 Warming in Alaska has caused insect outbreaks to increase. Red areas indicate spruce beetle infestations on the Kenai Peninsula. R50
142 2nd Public Review Draft, January 2009
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Regional Climate Impacts: Alaska
L1 Prior to 1990, the spruce budworm was not able to Ponds in Alaska are Shrinking (1951-2000) R1
L2 reproduce in interior Alaska9. Hotter, drier sum- Yukon Flats National Wildlife Refuge, northeastern interior R2
L3 mers, however, now mean that the forests there are R3
L4 threatened by an outbreak of spruce budworms13. R4
L5 This trend is expected to increase in the future if R5
L6 summers in Alaska become hotter and drier9. Large R6
L7 areas of dead trees, such as those left behind by R7
L8 pest infestations, are highly flammable and thus R8
L9 much more vulnerable to wildfire than living trees. R9
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L11 The area burned in North America’s northern forest R11
L12 that spans Alaska and Canada tripled from the R12
L13 1960s to the 1990s. Two of the three most exten- R13
L14 sive wildfire seasons in Alaska’s 56-year record R14
L15 occurred in 2004 and 2005, and half of the most R15
L16 severe fire years on record have occurred since R16
L17 199014. Under changing climate conditions, the av- R17
Riordan et al.18
L18 erage area burned per year in Alaska is projected to R18
Ponds across Alaska have shrunk as a result of increased evaporation
L19 double by the middle of this century10. By the end and permafrost thawing. The pond in the top pair of images shrunk
R19
L20 of this century, area burned by fire is projected to from 180 to 10 acres; the larger pond in the bottom pair of images R20
L21 triple under a moderate greenhouse gas emissions shrunk from 90 to 4 acres. R21
L22 scenario and to quadruple under a higher emissions R22
L23 scenario†. Such increases in area burned would millions of waterfowl and shorebirds that winter in R23
L24 result in numerous impacts, including hazardous the lower 48 states. Wetlands are also important to R24
L25 air quality conditions such as those suffered by Native peoples who hunt and fish for their food in R25
L26 residents of Fairbanks during the summers of 2004 interior Alaska. Many villages are located adjacent R26
L27 and 2005, as well as increased risks to rural Native to wetlands that support an abundance of wildlife R27
L28 Alaskan communities because of reduced availabil- resources. The sustainability of these traditional R28
L29 ity of the fish and game that make up their diet15. lifestyles is thus threatened by a loss of wetlands. R29
L30 Such impacts on food security have the potential R30
L31 for significant impacts on health; shifts from a R31
L32 traditional diet to a more “Western” diet are known Thawing permafrost damages roads, R32
L33 to be associated with increased risk of cancers, runways, water and sewer systems, and R33
L34 diabetes, and cardiovascular disease16. other infrastructure. R34
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L36 Permafrost temperatures have increased throughout R36
L37 Lakes are declining in area. Alaska since the late 1970s19. The largest increases R37
L38 have been measured in the northern part of the R38
L39 Across the southern two-thirds of Alaska, the area state20. While permafrost in interior Alaska so far R39
L40 of closed-basin lakes (lakes without stream inputs has experienced less warming than permafrost in R40
L41 and outputs) has decreased over the past 50 years. northern Alaska, it is more vulnerable to thawing R41
L42 This is likely due to the greater evaporation and during this century because it is generally just R42
L43 thawing of permafrost that result from warming17,18. below the freezing point, while permafrost in R43
L44 A continued decline in the area of surface water northern Alaska is colder. R44
L45 would present challenges for the management of R45
L46 natural resources and ecosystems on National Land subsidence (sinking) associated with the R46
L47 Wildlife Refuges in Alaska. These refuges, which thawing of permafrost presents substantial chal- R47
L48 cover over 77 million acres (21 percent of Alaska) lenges to engineers attempting to preserve infra- R48
L49 and comprise 81 percent of the U.S. National Wild- structure in Alaska21. Public infrastructure at risk R49
L50 life Refuge System, provide a breeding habitat for for damage includes roads, runways, and water R50
2nd Public Review Draft, January 2009 143
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The U.S. Climate Change Science Program Global Climate Change Impacts in the United States
L1 Permafrost Temperature and sewer systems. It is estimated that thawing R1
L2 Deadhorse, northern Alaska AK
Permafrost Temperature 65 feet beneath Deadhorse, permafrost would add between $3.6 billion and R2
L3 21 $6.1 billion (10 to 20 percent) to future costs for R3
Temperature at 65.5 ft. depth (oF)
L4 publicly owned infrastructure by 2030 and between R4
L5 20 $5.6 billion and $7.6 billion (10 to 12 percent) by R5
Year
L6 208022. Analyses of the additional costs of perma- R6
Community
L7 19 frost thawing to private property have not yet 2027
Buildings been R7
L8 conducted.
Landing Strip 2022 R8
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2017 R9
L10 Thawing ground also has implications for oil and 2012 R10
L11 17 gas drilling. As one example, the number of days 2007 R11
L12 1980 1985 1990 1995 2000 2005
per year in which travel on the tundra is allowed R12
L13 Year
24
Nunder Alaska Department 0 Natural Resources Feet
of 250 500 750 1000 R13
Brown and Romanovsky 1 inch equals 500 feet
L14 Permafrost temperatures have risen throughout Alaska, with the largest standards has dropped from more than 200 to about
Image dated June 2004 R14
L15 increases in the northern part of the state. 100 days in the past 30 years. This results in a 50 R15
L16 percent reduction in days that oil and gas explora- R16
L17
Changing Permafrost Distribution tion and extraction equipment can be used2,23. R17
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Moderate Warming Scenario
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L20 Coastal storms increase risks to villages R20
L21 and fishing fleets. R21
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L23 Alaska has more coastline than the other 49 states R23
L24 combined. Frequent storms in the Gulf of Alaska R24
L25 and the Bering, Chukchi, and Beaufort seas already R25
L26 affect the coasts during much of the year. Alaska’s R26
L27 coastlines, many of which are low in elevation, are R27
L28 increasingly threatened by a combination of the R28
L29 Busey et al.25 loss of their protective sea ice buffer, increasing R29
L30 The graph shows projected thawing on the Seward Peninsula by the end storm activity, and thawing coastal permafrost. R30
L31 of this century under a moderate warming scenario (Intergovernmental R31
L32 Panel on Climate Change scenario A1B, which is approximately half- R32
way between the low- and high-emissions scenarios† used elsewhere
L33 R33
in this report).
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L36 Adaptation: Keeping Soil Around the Pipeline Cool R36
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L38 When permafrost thaws, it can cause the soil to R38
L39 sink or settle, damaging structures built upon or R39
L40 within that soil. A warming climate and burial of R40
L41 supports for the Trans-Alaska Pipeline System both R41
L42 contribute to thawing of the permafrost around the R42
L43 pipeline. In locations on the pipeline route where R43
L44 soils were ice-rich, a unique above-ground system R44
L45 was developed to keep the ground cool. Thermal R45
L46 siphons were designed to disperse heat to the air R46
L47 that would otherwise be transferred to the soil, and R47
L48 these siphons were placed on the pilings that support R48
L49 the pipeline. While this unique technology added significant expense to the pipeline R49
L50 construction, it helps to greatly increase the useful lifetime of this structure26. R50
144 2nd Public Review Draft, January 2009
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Regional Climate Impacts: Alaska
L1 Projected Coastal Erosion Increasing storm activity in autumn R1
Newtok, western Alaska
L2 in recent years27 has delayed or R2
L3 prevented barge operations that R3
Year
L4 supply coastal communities with R4
Community
L5 Buildings 2027 fuel. Commercial fishing fleets and R5
L6 Landing Strip 2022 other marine traffic are also strongly R6
L7 2017 affected by Bering Sea storms. R7
L8 2012 High-wind events have become R8
L9 2007 more frequent along the western and R9
L10 northern coasts. The same regions R10
L11 N are experiencing increasingly long R11
0 250 500 750 1000 Feet
L12 1 inch equals 500 feet sea-ice-free seasons and hence longer R12
L13 Image dated June 2004 periods during which coastal areas R13
U.S. Army Corps of Engineers28
L14 are especially vulnerable to wind and R14
Many of Alaska’s coastlines are eroding rapidly; the disappearance of coastal
L15 land is forcing communities to relocate. The 2007 line on the image indicates wave damage. Downtown streets in R15
L16 where Newtok, Alaska’s shoreline had eroded to by 2007. The other lines Nome, Alaska, have flooded in recent R16
L17 are projected assuming a conservative erosion rate of 36 to 83 feet per year; years. Coastal erosion is causing the R17
L18 however, Newtok residents reported a July 2003 erosion rate of 110 feet shorelines of some areas to retreat at R18
per year.
L19 average rates of tens of feet per year. R19
L20 The ground beneath several native R20
L21 communities is literally crumbling into the sea, forcing residents to confront difficult and expensive choices R21
L22 between relocation and engineering strategies that require continuing investments despite their uncertain R22
L23 effectiveness (see Society sector). R23
L24 R24
L25 Over the coming century, an increase of sea surface temperatures and a reduction of ice cover are likely R25
L26 to lead to northward shifts in the Pacific storm track and increased impacts on coastal Alaska29,30. Climate R26
L27 models project R27
L28 the Bering Sea R28
L29 to experience the Barrow Annual Number of Storms at Barrow, Alaska R29
(northernmost town in the United States)
L30 largest decreases in R30
L31 atmospheric pres- 35 R31
L32 sure in the Northern Open water (smoothed) R32
L33 Hemisphere, suggest- 30 Freeze up (smoothed)
R33
L34 ing an increase in R34
Number of Storms
Open water (raw)
L35 storm activity in the 25 Freeze up (raw)
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L36 region3. In addition, R36
L37 the longer ice-free 20 R37
L38 season is likely to R38
L39 make more heat and 15 R39
L40 moisture available for R40
L41 storms in the Arctic 10 R41
L42 Ocean, increasing R42
L43 their frequency and/ 5 R43
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L49 The observed increase in coastal storms threatens commercial activity and communities in Alaska. Black R49
and blue lines indicate the number of open-water storms (storms occurring in ice-free water); green and
L50 purple lines indicate the number of freeze-up storms (storms occurring with sea ice present). R50
2nd Public Review Draft, January 2009 145
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The U.S. Climate Change Science Program Global Climate Change Impacts in the United States
L1 Displacement of marine species will and location of the ice edge in spring. As the sea ice R1
L2 affect key fisheries. retreats, the location, timing, and species composi- R2
L3 tion of the blooms changes, reducing the amount of R3
L4 Alaska leads the United States in the value of its food reaching the living things on the ocean floor. R4
L5 commercial fishing catch. Most of the nation’s This radically changes the species composition and R5
L6 salmon, crab, halibut, and herring come from populations of fish and other marine life forms, R6
L7 Alaska. In addition, many Native communities with significant repercussions for fisheries34 (see R7
L8 depend on local harvests of fish, walruses, seals, Ecosystems sector). R8
L9 whales, seabirds, and other marine species for their R9
L10 food supply. Climate change causes significant Over the course of this century, changes already R10
L11 alterations in marine ecosystems with important observed on the shallow shelf of the northern R11
L12 implications for fisheries. Ocean acidification as- Bering Sea are likely to affect a much broader por- R12
L13 sociated with a rising carbon dioxide concentration tion of the Pacific-influenced sector of the Arctic R13
L14 represents an additional threat to cold-water marine Ocean. As such changes occur, the most productive R14
L15 ecosystems32,33 (see Ecosystems sector and Coasts commercial fisheries are likely to become more R15
L16 region). distant from existing fishing ports and processing R16
L17 infrastructure, requiring either relocation or greater R17
L18 One of the most productive areas for Alaska investment in transportation time and fuel costs. R18
L19 fisheries is the northern Bering Sea off Alaska’s These changes also will affect the ability of native R19
L20 west coast. The world’s largest single fishery is the peoples to successfully hunt and fish for the food R20
L21 Bering Sea pollock fishery, which has undergone they need to survive. Coastal communities already R21
L22 major declines in recent years. Over the past are noticing a displacement of walrus and seal R22
L23 decade, as air and water temperatures rose, sea ice populations. Bottom-feeding walrus populations R23
L24 in this region declined sharply. Populations of fish, are threatened when their sea ice platform retreats R24
L25 seabirds, seals, walruses, and other species depend from the shallow coastal feeding grounds on which R25
L26 on plankton blooms that are regulated by the extent they depend35. R26
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Mueter and Litzow36
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As air and water temperatures rise, marine species are moving northward, affecting fisheries, ecosystems, and
L48 coastal communities that depend on the food source. On average, by 2006, the center of the range for the examined R48
L49 species moved 19 miles north of their 1982 locations. R49
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146 2nd Public Review Draft, January 2009
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