Coastal Impacts, Adaptation, and Vulnerabilities - Climate ...

46 Coastal Impacts, Adaptation, and Vulnerabilitiessurge, is expected to substantially increase the frequency of flooding in major metropolitanareas in the U.S. northeast in the 21st century (Kirschen et al., 2008) and in California(Moser & Tribbia, 2006).Flooding and erosion are significant problems for many Native American villages inAlaska from the combined effects of sea-level rise, loss of protective sea ice (ACIA, 2005;Polyak et al., 2009), major storms, heavy inland rainfall that causes rivers to flood downstream,and accelerated melting of snow and ice (GAO, 2003, 2009).2.7 Temperature Change Impacts with a Focus on AlaskaTemperature TrendsIn Alaska, temperature increases melt permafrost and sea ice, which will exacerbate acceleratingcoastal erosion rates, especially on the North and West Coast.Temperature increases affect coasts due to sea-level rise associated with ocean thermalexpansion and terrestrial ice melt (see section 2.2). In addition to multi-year trends,water temperature variations occur seasonally. Changes can be small and difficult todetect (Willis et al., 2008), but they do contribute to overall coastal water level and, whencombined with other factors, could contribute to increased water levels. Biological activity(section 3.1) in coastal regions is likely to be adversely affected by temperatureincreases (Vaquer-Sunyer & Duarte, 2011). When combined with other stressors, coastalmarine productivity could become increasingly threatened.Much of the ocean off of the U.S. West Coast is an upwelling zone. The eastern PacificOcean circulation is manifested in this region as the southward-flowing Californiacurrent. The southward movement of an ocean current along a western coastal marginresults in surface waters moving away from the coast, which draws cool water up fromdeeper waters. Altering the strength of the ocean circulation will alter the upwellingregime; this linkage to atmospheric circulation represents the primary mechanism foraltering West Coast ocean temperature. Currently, the response of this circulation regimeto projected climate forcing is not well known. For most West Coast areas, datasuggest no change or a decrease in sea surface temperatures, measured by season. Onlyin southern California are increasing trends observed, and only during the strongestseason, autumn, and the weaker season, winter (Pardo et al., 2011); however, decreasingcoastal ocean temperatures could result in decreased regional precipitation by reducingevaporation and, in the same manner as a temperature increase, could act to stress themarine biota. At the same time, a cooler ocean surface could act to reduce the intensity ofcoastal storms. Finally, cooler waters could also lead to an increase in the occurrence offog, which impacts the transportation sector.The nearshore waters of the U.S. Atlantic and Gulf of Mexico coasts are much warmerwaters than the waters of the U.S. West Coast. Like the West Coast, ocean temperaturesalong the U.S. East Coast are largely a function of ocean circulation patterns, in this case,the Gulf Stream. In the Atlantic, a primary response to a change in ocean temperaturesis a change in hurricane formation and trajectory. Warmer waters favor hurricane formation,longevity, and power, but recent work suggests that atmospheric responses towarm waters of the “Atlantic Warm Pool,” which include the Gulf of Mexico, Caribbean