2014/07/16 Council Agenda Packet

21: NORTHWEST evaluation calculated projected sea level rise and ranges for the years 2030, 2050, and 2100 (relative to 2000) based on latitude for Washington, Oregon, and California (see Figure 21.3).50 In addition to long-term climate -driven changes in sea level projected for the Northwest, shorter -term El Nino conditions can increase regional sea level by about 4 to 12 inches for periods of many months.5o53 Northwest coastal waters, some of the most productive on the West Coast,54 have highly variable physical and ecological con- ditions as a result of seasonal and year-to-year changes in up - welling of deeper marine water that make longer -term changes difficult to detect. Coastal sea surface temperatures have in- creased55 and summertime fog has declined between 1900 and the early 2000s, both of which could be consequences of weaker upwelling winds.56 Projected changes include increas- ing but highly variable acidity,57'58'59 increasing surface water temperature (2.2°F from the period 1970 to 1999 to the period 2030 to 2059),60 and possibly changing storminess.61 Climate models show inconsistent projections for the future of North- west coastal upwelling.12'62 Consequences and Likelihoods of Changes In Washington and Oregon, more than 140,000 acres of coastal lands lie within 3.3 feet in elevation of high tide.63 As sea levels continue to rise, these areas will be inundated more frequently. Many coastal wetlands, tidal flats, and beaches will probably decline in quality and extent as a result of sea level rise, particularly where habitats cannot shift inland because of topographical limitations or physical barriers resulting from human development. Species such as shorebirds and forage fish (small fish eaten by larger fish, birds, or mammals) would be harmed, and coastal infrastructure and communities would be at greater risk from coastal storms.64 Ocean acidification threatens culturally and commercially significant marine species directly affected by changes in ocean chemistry (such as oysters) and those affected by changes in the marine food web (such as Pacific salmon65). Northwest coastal waters are among the most acidified worldwide, especially in spring and summer with coastal upwelling5859'66 combined with local factors in estuaries.57'58 Increasing coastal water temperatures and changing ecological conditions may alter the ranges, types, and abundances of marine species.67'68 Recent warm periods in the coastal ocean, for example, saw the arrival of subtropical and offshore marine species from zooplankton to top predators such as striped marlin, tuna, and yellowtail more common to the Baja area.69 Warmer water in regional estuaries (such as Puget Sound) may contribute to a higher incidence of harmful blooms of algae linked to paralytic shellfish poisoning,7° and may result in adverse economic impacts from beach closures affecting recreational harvesting of shellfish such as razor clams.'' Toxicity of some harmful algae appears to be increased by acidification.'2 Rising Sea Levels and Changing Flood Risks in Seattle Figure 21.4. Areas of Seattle projected by Seattle Public Utilities to be below sea level during high tide (Mean Higher High Water) and therefore at risk of flooding or inundation are shaded in blue under three levels of sea level rise,'$ assuming no adaptation. (High [50 inches] and medium [13 inches] levels are within the range projected for the Northwest by 2100; the highest level [88 inches] includes the compounding effect of storm surge, derived from the highest observed historical tide in Seattle79). Unconnected inland areas shown to be below sea level may not be inundated, but could experience problems due to areas of standing water caused by a rise in the water table and drainage pipes backed up with seawater. (Figure source: Seattle Public Utilities80). Many human uses of the coast — for living, working, and recreating — will also be negatively affected by the physical and ecological consequences of climate change. Erosion, inundation, and flooding will threaten public and private property along the coast; infrastructure, including wastewater treatment plants;7'73 stormwater outfalls;74'75 ferry terminals;76 and coastal road and rail transportation, especially in Puget Sound.77 Municipalities •from Seattle74 and Olympia,75 Washington, to Neskowin, Oregon, have mapped risks from the combined effects of sea level rise and other factors. U.S. GLOBAL CHANGE RESEARCH PROGRAM 493 CLIMATE CHANGE IMPACTS IN THE UNITED STATES