Sea-Level Rise for the Coasts of California, Oregon, and Washington Past, Present, and Future (2012) / Chapter Skim
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4 Sea-Level Variability and Change off the California, Oregon, and Washington Coasts
4 Sea-Level Variability and Change off the California, Oregon, and Washington Coasts
Pages 55-82
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From page 55... ...
. Spatial variability pressures associated with El Niños and other climate in the North Pacific Ocean is associated with climate patterns can significantly elevate sea level along the patterns -- primarily the El Niño-Southern Oscillawest coast of the United States for intervals of several tion (ENSO)
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From page 56... ...
(Bottom) History the tropical Pacific, including sea-level pressure, surface of the PDO index (the principal component of monthly sea wind, sea surface temperature, surface air temperature, surface temperature anomalies in the North Pacific Ocean and cloudiness.
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From page 57... ...
. Recent studies show a decrease during one of the largest El Niños in half a century, in the rate of sea-level rise along the west coast of the seven tide gages along the west coast (San Diego, Los United States since 1993, which is consistent with Angeles, Monterey, Crescent City, Charleston, Astoria, IPCC (2007)
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From page 58... ...
, the difference between mean sea level for 19932009 and sea level during the December 1997 El Niño.
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From page 59... ...
west coast often corresponds Any climate-induced increase in storm frequency to forcing by regional and basin-scale winds associ- and magnitude will induce short-term changes in sea ated with climate patterns such as the PDO and the level. This issue is critical to coastal planners because North Pacific Gyre Mode (e.g., Lagerloef, 1995; Fu storm surges and wind-driven waves are responsible for and Qiu, 2002; Jevrejeva et al., 2006; Cummins and most of the flooding and erosion damage along the west Freeland, 2007; Miller and Douglas, 2007; Di Lorenzo coast of the United States (Armstrong and Flick, 1989; et al., 2008, 2010; Bromirski et al., 2011; Sturges and Domurat and Shak, 1989; Allan and Komar, 2006)
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From page 60... ...
west coast tide gages. California.
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From page 61... ...
. The wind and pressure patterns wave heights at some California locations, but not that elevate sea level above climatological normals along everywhere along the west coast (Allan and Komar, the west coast also may occur in winters when El Niño 2006)
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From page 62... ...
. FIGURE 4.6 Atmospheric circulation during periods of high waves along the central California coast exhibits broad-scale low pressure over the North Pacific.
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From page 63... ...
Several climate models with a deepening of the winter low pressure system over discussed in the IPCC Fourth Assessment Report the North Pacific Basin and partly to the incidence of project that the mid-latitude storm tracks in both some relatively strong El Niño years since 1995. the southern and northern hemispheres will migrate Increases in wind speed and wave heights in the poleward over the 21st century (Meehl et al., 2007)
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From page 64... ...
, resulting in significant vertical land motions in the vicinity of the California, Periods of anomalously high sea levels and wave Oregon, and Washington coasts. In contrast, modern heights along the west coast of the United States ex- melting affects land motions at the ice masses, which hibit considerable variability on synoptic, interannual, are far from the U.S.
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From page 65... ...
First, that melting of Alaska glaciers creates a strong norththe large mass of glaciers and ice sheets generates an south gradient in relative sea-level change along the additional gravitational pull that draws ocean water west coast. The gradient from uniform melting of the closer, raising relative sea level near the ice masses.
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From page 66... ...
(B) Response to uniform melting over the entire grounded portion of the Greenland Ice Sheet.
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From page 67... ...
for 19922008. TABLE 4.1 Ice Loss Rates, Fingerprint Scale Factors, and Adjusted Rates of Relative Sea-Level Rise for Three West Coast Locations North Coast Central Coast South Coast Adjusted Adjusted Adjusted Ice Mass Loss Rate Scale Sea-Level Rise Scale Sea-Level Rise Scale Sea-Level Rise Ice Source (mm yr-1 SLE)
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From page 68... ...
WEST COAST to the oceans and the consequent subsidence of the ocean basins in response to the increased water load Vertical land movements that affect relative sea produce a change in the absolute sea level (or geoid, level may be caused by geologic processes (e.g., glacial an equipotential surface of the Earth's gravity field that isostatic adjustment, tectonics, compaction) or anthro- coincides with the mean sea surface)
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From page 69... ...
They change," "radial displacement," and "vertical motion" differ in the relative thickness of the ice sheet, which also are used interchangeably. in the case of ICE-6G has been adjusted to eliminate The committee compared the GIA predictions of the misfits between the vertical motion predictions of relative sea-level change at 21 tide gage locations in the model and the GPS observation analyses by ArCalifornia, Oregon, and Washington from an ensemble gus and Peltier (2010)
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From page 70... ...
Vertical land motions for the C ascadia The U.S. west coast is characterized by two tec- Subduction Zone and San Andreas Fault Zone are tonically distinct regions: (1)
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From page 71... ...
. To estimate interseismic de Along much of the Oregon and Washington coasts, formation along the Washington and Oregon coasts, the earthquake cycle yields a characteristic pattern of the committee used results from the CAS3D-2 model vertical land movements (Figure 4.11)
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From page 72... ...
be experiencing subsidence. Comparisons of the model San Andreas Fault Zone projections with GPS data are discussed below (see "Current Rates of Vertical Land Motion Along the Unlike the Cascadia Subduction Zone, vertical U.S.
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From page 73... ...
. A comprehensive from the Mississippi Delta and found compaction rates analysis of tectonically induced vertical land motions of 5 mm yr-1 on millennial timescales and more than for the San Andreas Fault Zone has not been done.
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From page 74... ...
west coast (see "Geographic Variation Along the U.S. West Coast" in Chapter 1)
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From page 75... ...
. static adjustment; most GIA models predict subsidence The spatial distribution of published data on verti- south of the Mendocino Triple Junction (gray band cal land motions is not optimal for assessing sea-level in Figure 4.14b; see also Sella et al., 2007; Mazzotti rise along the west coast.
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From page 76... ...
Vertical land motion differs on the west and east side of the Palos Verdes Peninsula. To the west, relative sea level was nearly constant from 1992 to 2000, with most values less than zero.
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From page 77... ...
(A) Map of the west coast of the United States showing major tectonic boundaries and locations of GPS stations color-coded for vertical land motion rates.
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From page 78... ...
The change in relative sea level is what coastal WEST COAST TIDE GAGE RECORDS residents experience and state and local managers factor into planning. To compare west coast sea-level The sea level along the west coast of the United trends with the global sea-level trend, it is necessary to States reflects contributions from both the global sea adjust the relative rates of sea-level rise for changes in level and the local and regional processes discussed atmospheric pressure and vertical land motions, both above.
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From page 79... ...
. The rate of sea-level rise at the tide gage, adData from all CGPS stations within a 15 km radius of justed for vertical land motion and atmospheric the gage also were analyzed to assess the spatial vari- pressure, is the slope of the red line in Figure 4.16, ability of vertical land motions near the tide gages.
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From page 80... ...
80 SEA-LEVEL RISE FOR THE COASTS OF CALIFORNIA, OREGON, AND WASHINGTON -128° -124° -120° -116° Friday Harbor Neah Bay 48° Seattle Astoria 44° Crescent City Cape Mendocino 40° San Francisco Alameda 36° Port San Luis mm/yr 3 0 Santa Monica Los Angeles -3 La Jolla San Diego 32° FIGURE 4.15 Rates of relative sea-level change estimated from long tide gage records (63108 years) analyzed in this report.
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From page 81... ...
to relative sea-level rise for 19922008 by about The highest sea levels recorded along the west coast 42 percent along the north coast (Neah Bay, Washare usually associated with El Niño events, which can ington) , 24 percent along the central coast (Eureka,
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From page 82... ...
When adjusted for vertical land mo Vertical land motions along the west coast of the tions and for atmospheric pressure effects, the rates of United States are caused by a complex combination of relative sea-level rise along the U.S. west coast are lower tectonics, glacial isostatic adjustment, sediment com- than the rate of global mean sea-level rise.
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