simulations, they obtained sea-level rise estimates of 3–12 cm by 2030 and 11–30 cm by 2050, relative to 2008, for the 11 locations.
Sea-level rise along the west coast of the United States differs from global mean sea-level rise because of local steric (primarily thermosteric) contributions, dynamic height differences caused primarily by changes in winds, the gravitational and deformational effects of modern land ice melting, and vertical land motions along the coast (see Chapter 4). The committee projected the contributions of these components to sea-level rise off the California, Oregon, and Washington coasts for the years 2030, 2050, and 2100, relative to year 2000. The local steric and wind-driven contribution was estimated using GCMs; the land ice contribution, adjusted for gravitational and deformational effects, was extrapolated; and the contribution from vertical land motion was estimated using Global Positioning System (GPS) data. Values for the individual contributions are summarized in Table 5.3 and discussed below.
Steric and Dynamic Ocean Height Effects
The local steric and wind-driven components were determined from the same CMIP 3 global ocean models used to calculate the steric contribution to global sea-level rise. Thirteen of the CMIP 3 models examined in Pardaens et al. (2010) include global annual averages of the steric contribution and wind-driven dynamic ocean heights on a 1° latitude by 1° longitude grid. From this data set, the committee selected the ocean model grid points closest to the coastlines of California, Oregon, and Washington at each latitude, developing a time series for each model at each latitude. To obtain values
TABLE 5.3 Regional Sea-Level Rise Projections (in cm) Relative to Year 2000
|Steric and dynamic oceana||3.6 ± 2.5||0.0-9.3 (B1-A1FI)||7.8 ± 3.7||2.2-16.1 (B1-A1H)||20.9 ± 7.7||9.9-37.1 (B1-A1F1)|
|Non-Alaska glaciers and ice capsb||2.4 10.2||4.4 ± 0.3||11.4 ±1.0|
|Alaska, Greenland, and Antarctica with sea-level fingerprint effectc|
|San Francisco, CA||7.8||6.1-9.6||17.6||12.7-22.3||57.6||37.3-76.1|
|Los Angeles, CA||8.0||6.3-9.6||17.9||13.0-22.3||58.5||38.6-76.4|
|Vertical land motiond|
|North of Cape Mendocino||-3.0||-7.5-1.5||-5.0||-12.5-2.5||-10.0||-25.0-5.0|
|South of Cape Mendocino||4.5||0.6-8.4||7.5||1.0-14.0||15.0||2.0-28.0|
|Sum of all contributions|
|Seattle||6.6 ± 5.6||-3.7-22.5||16.6 ± 10.5||-2.5-47.8||61.8 ± 29.3||10.0-143.0|
|Newport||6.8 t 5.6||-3.5-22.7||17.2 ± 10.3||-2.1-48.1||63.3 ± 28.3||11.7-142.4|
|San Francisco||14.4 ± 5.0||4.3-29.7||28.0 ± 9 2||12.3-60.8||91.9 ± 25.5||42.4-166.4|
|Los Angeles||14.7 ± 5.0||4.6-30.0||28.4 ± 9.0||12.7-60.8||93.1 - 24.9||44.2-166.5|
a Projection indicates the mean and ± standard deviation computed for the Pacific coast from the gridded data presented in Pardaens et al. (2010) for the A1B scenario. Ranges are the means for B1 and A1Fl using the scaling in Table 10.7 of IPCC (2007; see also Table 5.1 of this report): (B1/A1B) = (0.1/0.13); (A1Fl/A1B) = (0.17/0.13).
b Extrapolated based on ice loss rates for glaciers and ice caps except Alaska, Greenland, and Antarctica. No ranges are given because these sources are assumed to have a small or uniform effect on the gradient in sea-level change along the U.S. west coast (see “Sea-Level Fingerprints of Modern Land Ice Change” in Chapter 4).
c Extrapolation based on ice loss rates and gravitational attraction effects for Alaska, Greenland, and Antarctica. Ranges reflect uncertainty in ice loss rates.
d Assumes constant rates of vertical land motion of 1.0 ± 1.5 mm yr-1 for Cascadia and -1.5 ± 1.3 mm yr-1 for the San Andreas region. The signs were reversed to calculate relative sea level. Uncertainties are 1 standard deviation.