Climate Change Impacts
Climate change presents significant risks to our nation's natural and cultural resources. Although climate change was once believed to be a future problem, there is now unequivocal scientific evidence that our planet's climate system is warming (Intergovernmental Panel on Climate Change, 2007). While many people understand that human emissions of greenhouse gases have contributed to recent observed climate changes, fewer are aware of the specific impacts these changes will bring.
To document these impacts, the National Park Service created a series of regional summaries to provide scientific findings about climate change and its effect on the national parks. The following are excerpts from Understanding the Science of Climate Change: Talking Points - Impacts to Alaska Maritime and Transitional (Natural Resource Report NPS/NRPC/NRR-2010).
From 1949 to 2009, regional mean annual temperatures for the Arctic, Interior, and West Coast of Alaska increased by 1.4 to 2.5°C (2.5 to 4.5°F) and the greatest change in mean seasonal temperatures (2.3 to 4.9°C, 4.1 to 8.8°F) was observed in the winter (Alaska Climate Research Center 2010).
Maximum temperature increases were observed throughout Alaska; the greatest increases were observed during the spring with an average increase of 0.46°C (0.83°F) per decade (Keyser et al. 2000). Average maximum temperatures increased per decade 0.14°C (0.25°F) in the summer and 0.24°C (0.43°F) in the winter (Keyser et al. 2000).
The greatest temperature increases in the Alaska Maritime and Transitional bioregion were observed during winter months. Air temperatures increased by 1.1 to 2.9° C (~ 2.0 to 5.2°F) between 1951 and 2001 (Hartmann and Wendler 2005). From the period 1948 to 2009, temperature increases throughout the region ranged from 0.5 to 2.7°C (0.1 to 4.9°F). The greatest temperature increases were observed in Talkeetna (+2.7°C, or 4.9°F), a community on the transitional area between maritime and boreal climate. Observed temperatures increased the least in the community of Kodiak (0.5°C, or 0.1°F), on the shores of Kodiak Island in the Gulf of Alaska, where temperatures are heavily moderated by ocean processes (Alaska Climate Research Center, Geophysical Institute et al. 2009).
In southern and southeast Alaska the annual mean diurnal temperature range (difference between daily maximum and minimum temperatures) decreased by 0.9 °C (1.62 °F), and the winter diurnal temperature range decreased by 1.8 °C (3.24 °F), between 1949 and 1998 (Stafford et al. 2000). Four of the 25 locations used in the study showed significant decreases for all seasons: Anchorage, Juneau, Seward, and Talkeetna (Stafford et al. 2000).
THE WATER CYCLE
The melting rate of glaciers throughout Alaska has increased in recent decades, as has their contribution to sea level rise (Dyurgerov and Meier 2000; Larsen et al. 2007a). From the mid 1990s to the early 2000s, the rate of glacial thinning in Alaska tripled compared to the mid 1950s to mid-1970s time period; the loss of ice during this period was equivalent to nearly twice the estimated annual loss of ice from the Greenland Ice Sheet. Over the last half of the 20th century, Alaska glaciers contributed the largest single measured glaciological contribution to sea level, with a total annual volume change of -52 ± 15 km3/year (12.3 ± 3.6 miles3) water equivalent, which equates to a rise in sea level of 0.14mm ± 0.04 mm/year, (0.006 ± 0.002 in/year). (Arendt et al. 2002).
The estimated total volume change of the Harding Icefield and associated glaciers, more than 50% of which are contained in Kenai Fjords National Park, decreased by 34 km3 (8.1 miles3), with an average decrease in elevation of 21 m (68.7 ft), between the 1950s and the mid-1990s (Aðalgeirsdóttir et al. 1998); this rate of thinning increased by 1.5 times between the mid-1990s and 1999 (Vanlooy et al. 2006).
The terminus of Exit Glacier, a main attraction in Kenai Fjords National Park, retreated a distance of 500m (1,635ft) and thinned by 80 to 90m (262 to 294ft) in the lower region between 1950 and 1990 (Aðalgeirsdóttir et al. 1998).
Between 1950 and 1996, over 80% of wetland sites surveyed on the Kenai Peninsula had experienced some degree of drying and nearly 66% of wetland sites had decreased in area (Klein et al. 2005).
Climate has demonstrably affected terrestrial ecosystems through changes in the seasonal timing of life-cycle events (phenology), plant-growth responses (primary production), and biogeographic distribution (Parmesan 2006; Field et al. 2007). Statistically significant shifts in Northern Hemisphere vegetation phenology, productivity, and distribution have been observed and are attributed to 20th century climate changes (Walther et al. 2002; Parmesan and Yohe 2003; Parmesan 2006).
Between 1980 and 2000, a trend toward earlier spring budburst and increased maximum leaf area at high northern latitudes was observed, mainly due to changes in temperature (Lucht et al. 2002).
On the Kenai Peninsula, wooded regions increased in area by 28% between 1950 and 1996,while open, wet, and watered areas decreased in size. Type shifts from wetlands to upland habitats were observed during the same time period (Klein et al. 2005).
Comparisons of historical (ca. late 1800s to early 1900s) photographs with current (2004 to 2006) photos reveal that following glacial retreat in national parks in southwest Alaska, coastal areas experienced a striking level of vegetation colonization, but vegetation colonization in higher elevation areas was less marked (Jorgenson and Bennett 2006).
Shrub expansion into uplands was documented along granitic ridges, where shrub cover increased from less than 50% between 1928 and 1929 to over 75% between 2004 and 2006 (Jorgenson and Bennett 2006). A preliminary comparison of aerial photographs from 1950 to 2005 in Kenai Fjords National Park documented conversion of two to 14% of barren areas to shrub cover, for all fjords studied. In Northwestern fjord, an area that is experiencing rapid glacial retreat, 39% of the areas that were once ice-covered have been converted to shrublands (Boucher et al. 2009).
A meta analysis of climate change effects on range boundaries in Northern Hemi-sphere species of birds, butterflies, and alpine herbs shows an average shift of 6.1 kilometers per decade northward (or meters per decade upward), and a mean shift toward earlier onset of spring events (frog breeding, bird nesting, first flowering, tree budburst, and arrival of migrant butterflies and birds) of 2.3 days per decade (Parmesan and Yohe 2003).
An 84% decline in Kittlitz's murrelets (Brachyramphus brevirostris), a diving seabird of relatively low abundance found only in Alaska and eastern Siberia, was observed in Prince William Sound from 1989 (6400 birds observed) to 2000 (1000 birds observed). During this period, bird distribution in the sound shifted from a fairly dispersed pattern to concentration in the northwest region. Fjords from which this species disappeared had receding glaciers as of the late 1980s, or had no direct glacial input, indicating a link between the decline of Kittlitz's murrelets and glacial recession (Kuletz et al. 2003).
Tree-ring records indicate that spruce bark beetle outbreaks have occurred on the Kenai Peninsula approximately every 52 years for the past 250 years, following 5 to 6 years of warm summer temperatures and mild winters. These warm temperatures likely influence spruce beetle population size through a combination of increased overwinter survival, a doubling of the maturation rate from 2 years to 1 year, and regional drought-induced stress of mature host trees; if the recent warming trend continues, endemic levels of spruce beetles will likely be high enough to perennially thin forests as soon as the trees reach susceptible size (Berg et al. 2006).
Relocating indigenous communities represents a large financial cost for governments, but also impacts the communities themselves, potentially resulting in loss of integral cultural elements such as access to traditional use areas for subsistence activities, loss of history and sense of intact community, and potential loss of social networks and extended kin support (Callaway 2007).
Some traditional subsistence practices are more expensive and time-consuming than in the recent past, due to difficult hunting conditions associated with climate change impacts. These changes can place a strain on subsistence communities, and in some cases can be a deterrent to engaging in traditional hunting at all; for example, as sea ice conditions change, marine mammals may follow sea ice retreat, altering their distribution and taking them out of range for some hunters (Berman and Kofinas 2004; Callaway 2007; Hanna 2007).
With increasing temperatures and more snow-free days, the length of the potential summer tourist season in Alaska is increasing (Alaska Climate Research Center 2009; Dye 2002).
A study at Kenai Fjords National Park determined sea level rise and wave height increases could impact park resources through erosion and loss of gravel beaches along rocky coastlines. These pocket beaches are currently used recreationally by sea kayakers (Pendleton et al. 2006).
This report is available from the Natural Resource Publications Management website. Please cite this publication as:
Jezierski, C., R. Loehman, and A. Schramm. 2010. Understanding the science of climate change: Talking points - impacts to Alaska Maritime and Transitional. Natural Resource Report NPS/NRPC/NRR-2010/223. National Park Service, Fort Collins, Colorado.
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