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1
Introduction
S
ea-level change is one of the most visible con- of the coast. For example, significant development
sequences of changes in the Earth's climate. A along the edge of central and southern San Francisco
warming climate causes global sea level to rise Bay--including two international airports, the ports of
principally by (1) warming the oceans, which causes San Francisco and Oakland, a naval air station, free-
sea water to expand, increasing ocean volume, and ways, housing developments, and sports stadiums--has
(2) melting land ice, which transfers water to the ocean. been built on fill that raised the land level only a few
Tide gage and satellite observations show that global feet above the highest tides. The San Francisco Inter-
sea level has risen an average of about 1.7 mm yr-1 national Airport will begin to flood with as little as
over the 20th century (Bindoff et al., 2007), which is 40 cm of sea-level rise (Figure 1.2), a value that could
a significant increase over rates of sea-level rise during be reached in several decades (Figure 1.1).
the past few millennia (Shennan and Horton, 2002; Coastal infrastructure and ecosystems are already
Gehrels et al., 2004). Projections suggest that sea level vulnerable to high waves during ocean storms (e.g.,
will continue to rise in the future (Figure 1.1). How- Figure 1.3), especially when storms coincide with high
ever, the rate at which sea level is changing varies from tides and/or El Niño events. For example, a strong El
place to place and with time. Along the west coast of Niño, combined with a series of large storms at times of
the United States, sea level is influenced by changes in high astronomical tides, caused more than $200 million
global mean sea level as well as by regional changes in dollars in damage (in 2010 dollars) to the California
ocean circulation and climate patterns such as El Niño; coast during the winter of 19821983 (Griggs et al.,
gravitational and deformational effects of ice age and 2005). Higher sea levels and heavy rainfall caused
modern ice mass changes; and uplift or subsidence flooding in low-lying areas and increased the level
along the coast. The relative importance of these factors of wave action on beaches and bluffs (Storlazzi and
in any given area determines whether the local sea level Griggs, 2000). More than 3,000 homes and businesses
will rise or fall and how fast it will change. were damaged, 33 oceanfront homes were completely
Sea-level change has enormous implications for destroyed, and roads, parks, and other infrastructure
coastal planning, land use, and development along was heavily damaged. The damage will likely increase
the 2,600 km shoreline of California, Oregon, and as sea level continues to rise and more of the shoreline
Washington (referred to hereafter as the U.S. west is inundated.
coast). Rising sea level increases the risk of flooding, In November 2008, Governor Arnold
inundation, coastal erosion, wetland loss, and saltwater Schwarzenegger issued Executive Order S-13-08 di-
intrusion into freshwater aquifers in many coastal com- recting California state agencies to plan for sea-level
munities (e.g., Heberger et al., 2009, 2011). Valuable rise and coastal impacts.1 Included in the executive
infrastructure, development, and wetlands line much
1 See .
9
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10 SEA-LEVEL RISE FOR THE COASTS OF CALIFORNIA, OREGON, AND WASHINGTON
FIGURE 1.1 Estimated, observed, and projected global sea-level rise from 1800 to 2100. The pre-1900 record is based on geological
evidence, and the observed record is from tide gages (red line) and satellite altimetry (blue line). Example projections of sea-level rise
to 2100 are from IPCC (2007) global climate models (pink shaded area) and semi-empirical methods (gray shaded area; Rahmstorf,
2007). SOURCES: Adapted from Shum et al. (2008), Willis et al. (2010), and Shum and Kuo (2011).
order was a request that the National Research Council fornia, Oregon, and Washington for 2030, 2050, and
(NRC) establish a committee to assess sea-level rise in 2100 (see Box 1.1 for the committee charge). The years
California to inform state planning and development for the assessment represent planning horizons: 2030
efforts. Prior to release of the NRC report, the state is a typical planning horizon for many local managers;
agencies were instructed to incorporate sea-level-rise 2050 is the latest date for which conventional popula-
projections into their planning process. The range of tion projections are available; and 2100 is the limit
projections adopted by California as interim values are beyond which uncertainties become too high for plan-
1321 cm for 2030, 2643 cm for 2050, and 78176 cm ning.2 The report primarily focuses on how much sea
for 2100 (CO-CAT, 2010). level is likely to rise globally (Task 1) and along the west
Following the California executive order, the states coast of the United States (Task 2). Processes that have
of Oregon and Washington, the U.S. Army Corps of only transient effects on sea level (e.g., tides, tsunamis)
Engineers, the National Oceanic and Atmospheric were considered only if the nature of the process affects
Administration, and the U.S. Geological Survey joined trends in sea level (e.g., changes in frequency of inten-
California in sponsoring this NRC study. These agen- sity of storms [Task 2a]). Coastal impacts or measures
cies need sea-level information for a variety of purposes, to lessen them were considered only in the context of
including assessing coastal hazard vulnerability, risks, summarizing what is known about how coastal habi-
and impacts; informing adaptation strategies; and im- tats and natural and restored environments respond to
proving coastal hazard forecasts and decision support and protect against future sea-level rise and storms
tools. (Tasks 2b and 2c).
This report provides an assessment of current
2 Jeanine Jones, California Department of Water Resources,
knowledge about changes in sea level expected in Cali-
personal communication, December 3, 2008.
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DISCLAIMER: The inundation data used in these maps do not account for shoreline protection or wave activity. These maps
INTRODUCTION
are for informational purposes only. Users agree to hold harmless and blameless the State of California and its representatives 11
and its agents for any liability associated with the use of the maps. The maps and data shall not be used to assess actual
coastal hazards,insurance requirements, or property values or be used in lieu of Flood Insurance Rate Maps issued by the
Federal Emergency Management Agency (FEMA).
South
San Francisco
San Francisco
Bay
Millbrae
NORTH
0 1.5 3 MILES
Sea level rise data provided by:
FIGURE 1.2 Expected inundation of low-lying areas, including the San Francisco International Airport (center), in the San Francisco
Bay Area with a Knowles,
SOURCE: 40 cmN. rise in
2008. sea S.W.
Siegel, level
and(light blue
P. A. M. shading).
Bachand, 2002. SOURCE: Bay Conservation and Development Commission,
12 SEA-LEVEL RISE FOR THE COASTS OF CALIFORNIA, OREGON, AND WASHINGTON
FIGURE 1.3 High surf during a high tide of nearly 2.7 m removed the front lawn of the Pacific Sands Resort at Neskowin, Oregon,
on January 9, 2008. SOURCE: Courtesy of Armand Thibault.
BOX 1.1
Committee Charge
The committee will provide an evaluation of sea-level rise for California, Oregon, and Washington for the years 2030, 2050, and 2100. The evalu-
ation will cover both global and local sea-level rise. In particular, the committee will
1. Evaluate each of the major contributors to global sea-level rise (e.g., ocean thermal expansion, melting of glaciers and ice sheets); combine
the contributions to provide values or a range of values of global sea-level rise for the years 2030, 2050, and 2100; and evaluate the uncertainties as-
sociated with these values for each timeframe.
2. Characterize and, where possible, provide specific values for the regional and local contributions to sea-level rise (e.g., atmospheric changes
influencing ocean winds, ENSO [El Niño-Southern Oscillation] effects on ocean surface height, coastal upwelling and currents, storminess, coastal
land motion caused by tectonics, sediment loading, or aquifer withdrawal) for the years 2030, 2050 and 2100. Different types of coastal settings will
be examined, taking into account factors such as landform (e.g., estuaries, wetlands, beaches, lagoons, cliffs), geologic substrate (e.g., unconsolidated
sediments, bedrock), and rates of geologic deformation. For inputs that can be quantified, the study will also provide related uncertainties. The study
will also summarize what is known about
a. climate-induced increases in storm frequency and magnitude and related changes to regional and local sea-level rise estimations (e.g.,
more frequent and severe storm surges);
b. the response of coastal habitats and geomorphic environments (including restored environments) to future sea-level rise and storminess
along the west coast;
c. the role of coastal habitats, natural environments, and restored tidal wetlands and beaches in providing protection from future inundation
and waves.
INTRODUCTION 13
and California (e.g., Cayan et al., 2009), and numerous Uncertainty in projecting climate-related sea-level
studies have been published on individual contributors changes arises from three sources: internal variability of
to sea-level change along the U.S. west coast. The the climate system, which fluctuates on interannual to
committee also analyzed tide gage records and Global multidecadal and longer timescales and on regional to
Positioning System data from California, Oregon, and global spatial scales; model uncertainty; and scenario
Washington for their local (around the station) and uncertainty (Hawkins and Sutton, 2009). The first is
regional (along the coast of one or more states) trends, particularly important for projections based on extrapo-
and extracted regional information from satellite lation of observations because observational records
altimetry data and glacial isostatic adjustment models.
tend to be short relative to the timescale of variability in
The most challenging aspect of the committee the climate system. Models have uncertainties because
charge was the projections of sea level for 2030, 2050, they are mathematical approximations that depart in
and 2100. The numerical global climate models devel- important ways from the actual system. Uncertainty
oped for the IPCC Fourth Assessment Report3 project in models used to describe key elements of sea-level
global sea-level rise to 2100. However, they do not change results from uncertainties in model parameters
account for rapid changes in the behavior of ice sheets (e.g., initial conditions, boundary conditions) as well as
and glaciers as melting occurs (ice dynamics) and thus structural uncertainties from incomplete understanding
likely underestimate future sea-level rise. The new suite of some climate processes or an inability to resolve the
of climate models for the Fifth Assessment Report was processes with available computing resources (Knutti et
not available at the time of writing this report. Conse- al., 2010). Finally, future emissions of greenhouse gasses
quently, the committee projected global sea-level rise and other factors that drive changes in the climate sys-
(Task 1) using model results from the IPCC Fourth tem depend on a collection of human decisions at local,
Assessment Report, together with a forward extrapola- regional, national, and international levels, as well as po-
tion of land ice that attempts to capture an ice dynamics tential but unknown technological developments. The
component. The committee also considered results IPCC deals with this uncertainty by providing a range
from semi-empirical projections, which are based on of possible futures (scenarios) based on assumptions
the observed correlation between global temperature about trends in concentrations of greenhouses gases and
and sea-level change (e.g., Vermeer and Rahmstorf, other influences on the climate (e.g., Moss et al., 2010).
2009). For the projections of sea-level rise along the This report uses both model and extrapolation
U.S. west coast (Task 2), the committee derived local approaches to make projections. Each approach has
values using regional ocean information extracted from different uncertainties (e.g., extrapolations take no
global models, GPS data from along the coast, and ice account of emission scenarios), which were combined
loss rates of large or nearby glaciers. into a single uncertainty range for the projections. Al-
though isolating the various sources of uncertainty may
Uncertainty have been useful for some applications (e.g., evaluating
costs and risks of various mitigation strategies), it was
In the IPCC Fourth Assessment Report, the major not required in the committee charge and would have
components of global sea-level rise were estimated at required a different analysis approach.
the 90 percent confidence level (Bindoff et al., 2007).
That is, values given as x ± e mean that there is a 90 per- OVERVIEW OF SEA-LEVEL CHANGE
cent chance that the true value is in the range x - e to
x + e. This report follows the IPCC convention unless Sea level is neither constant nor uniform every-
specified otherwise. where, but changes continually as a result of interact-
ing processes that operate on timescales ranging from
hours (e.g., tides) to millions of years (e.g., tectonics).
3 More than 20 such models from around the world were Processes that affect ocean mass, the volume of ocean
analyzed and compared through the World Climate Research water, or sea-floor topography cause sea level to change
Program's Coupled Model Intercomparison Project (CMIP3). See on global scales. On local and regional scales, sea level is
.
14 SEA-LEVEL RISE FOR THE COASTS OF CALIFORNIA, OREGON, AND WASHINGTON
also affected by vertical land motions and local climate that period, ice sheets covered much of North America,
and oceanographic changes. The primary factors that northern Europe, and parts of Asia, and sea levels were
contribute to global and local sea-level change are illus 125135 m lower than present (Peltier and Fairbanks,
trated in Figure 1.4 and discussed below. 2006; Clark et al., 2009). The onset of deglaciation
more than 20,000 years ago (Peltier and Fairbanks,
Global Sea-Level Change 2006) caused sea level to rise at an average rate of about
10 mm yr-1 (Alley et al., 2005). Empirical and glacial
Global sea level has varied significantly through- isostatic modeling studies suggest that the rate of ice
out Earth's history. Sediment and ice-core records of melt dropped significantly 7,000 years ago (Gehrels,
these changes provide a pre-anthropogenic context 2010), then declined steadily to a value of zero change
for understanding the nature and causes of current around 2,000 years ago (Fleming et al., 1998; Peltier,
and future changes. Over the past 2.5 million years, 2002b; Peltier et al., 2002). Geological data from salt
large continental ice sheets grew during long inter- marshes show a clear acceleration from relatively low
vals of cold global temperatures (glacial periods or ice rates of sea-level change during the past two millennia
ages) and retreated during intervals of warm global (order 0.25 mm yr-1; Figure 1.5) to modern rates (order
temperatures (interglacial periods). Traces of paleo- 2 mm yr-1) sometime between 1840 and 1920 (Kemp
shorelines, found along many of the world's coastlines, et al., 2011).
provide robust evidence that global mean sea level was Since the industrial era began, changes in global
at least 6 m higher during the last interglacial period sea level have been driven in part by the accumulation
(~116,000130,000 years ago) than at present (Kopp et of greenhouse gases in the atmosphere, which trap
al., 2009). During the Last Glacial Maximum (~26,000 heat and raise global temperatures. The primary pro-
years ago), approximately 40 × 106 km3 of sea water was cesses responsible for modern sea-level rise are thermal
transferred to the continents and stored as ice. During expansion of ocean water and melting from glaciers,
Oceanatmosphere
interaction Terrestrial water
Ice storage
melting
Gravitational
attraction of ice Groundwater withdrawal
Ocean circulation
Density
changes
Glacial isostatic Uplift and
adjustment subsidence
FIGURE 1.4 Processes that influence sea level on global to local scales. SOURCE: Modified from Milne et al. (2009).
INTRODUCTION 15
Sea-Level Estimates
Proxy reconstructions
0.2
Observations (tide gauges)
Sea Level (m)
Model
0.0
-0.2
rate of
sea-level 0 mm/yr +0.6 mm/yr -0.1 mm/yr +2.1
rise (mm/yr)
0 500 1000 1500 2000
Year (AD)
FIGURE 1.5 Sea-level estimates for the past 2000 years, adjusted for glacial isostatic effects, from proxy (geological) evidence
(blue), tide gage observations (green), and modified semi-empirical model hindcasts (red). Dotted red line shows where the model
hindcast deviates from the proxy record. The lower panel shows rates of sea-level change in mm yr-1 based on the proxy reconstruc-
tions. SOURCE: Data from Jevrejeva et al. (2008), Vermeer and Rahmstorf (2009), and Kemp et al. (2011).
ice caps, and the Greenland and Antarctic ice sheets circulation are driven primarily by changes in winds
(Figure 1.6). Changes in the amount of water stored in and ocean surface density associated with the El Niño-
land reservoirs have a smaller effect on global sea level. Southern Oscillation (ENSO), which has a period of 2
In general, groundwater extraction transfers water to to 7 years, and the Pacific Decadal Oscillation, which
the ocean and causes sea level to rise, and filling of land has a typical period of several decades. During a strong
reservoirs causes sea level to fall. El Niño, a pulse of warm water in the eastern equatorial
Pacific moves northward, forming a bulge in sea level
Local and Regional Sea-Level Change Along the along the California, Oregon, and Washington coasts.
U.S. West Coast The low atmospheric pressures and west-southwest
winds induced by an El Niño further elevate sea levels,
Relative (or local) sea level is the mean level of the which can reach 30 cm above normal levels for several
sea with respect to the land, both of which change with months (Komar et al., 2011). Sea level is lower along
time, as summarized below. the U.S. west coast during cooler La Niña conditions.
Large storms raise coastal sea level for the dura-
Changes in Ocean Levels tion of the storm, usually several hours. The path and
propagation speed of storms dictate wind direction and
Sea level in the Pacific Ocean is affected by ocean changes in barometric pressure, which in turn influence
circulation, short-term climate variations, storms, and wind waves and high water. The strongest winds and
gravitational and deformational effects of land ice hence the biggest waves along the west coast of the
changes. Changes in ocean circulation affect regional United States are typically generated during winter
sea level on seasonal to decadal and longer timescales storms. Large waves along the California coast are
by redistributing ocean mass and altering seawater tem- also generated by tropical storms that reach the eastern
perature and salinity patterns. These changes in ocean Pacific in summer and early fall.
16 SEA-LEVEL RISE FOR THE COASTS OF CALIFORNIA, OREGON, AND WASHINGTON
FIGURE 1.6 IPCC (2007) estimates of the primary contributions to global mean sea-level change for 1961 to 2003 (blue) and
for 1993 to 2003 (brown), compared to the observed rate of global sea-level rise from tide gages and satellite altimetry. The bars
represent the 90 percent error range. The relative contributions of these components has changed in recent years, as discussed in this
report. SOURCE: Figure 5.21 from Bindoff et al. (2007).
Finally, the large mass of glaciers and ice sheets last ice age, tectonics, compaction of sediments, and
exerts an additional gravitational pull that draws ocean the removal or addition of fluids from underground
water closer. As the ice melts, the gravitational pull de- reservoirs. During the last glacial maximum, the weight
creases, ice melt is transferred to the ocean, and the land of the ice depressed the land under the ice mass. As
and ocean basins deform in response to the loss of land the ice melted, the land beneath rose at rates up to
ice mass. These gravitational and deformational effects 50100 mm yr-1 (e.g., Shaw et al., 2002), and the ocean
create regional patterns of sea-level change. Modern floor subsided as ice melt was added to the ocean basins,
melting of ice masses that are nearby (Alaska glaciers) exerting a considerable load (on the order of 100 t m-2
or large (Greenland and Antarctic ice sheets) has the for a sea-level rise of 100 m; Figure 1.7). These isostatic
largest effect on sea level in the northeast Pacific Ocean, adjustments produced a characteristic pattern of sea-
reducing the land ice contribution to local sea-level rise level change, with land uplift and relative sea-level fall
on the order of tens of percent. The influx of fresh melt near the major ice centers, and relative sea-level rise
water to the ocean also decreases seawater salinity and everywhere else. Box 1.2 illustrates the effect of glacial
thus density near shore, which further contributes to isostatic adjustment on relative sea level along the west
regional sea-level variations. coast of the United States over the past 18,000 years.
The west coast of the United States is tectoni-
Changes in Land Levels cally active, straddling three plate boundaries: the
North American and Pacific plates, which slide past
Regional and local land motion along the U.S. one another along the San Andreas Fault Zone in
west coast is caused by the ongoing response of the California, and the Juan de Fuca plate, which subducts
solid earth to a massive loss of ice at the end of the under the North American plate along the Cascadia
INTRODUCTION 17
along the San Andreas Fault Zone have less impact on
sea level because the primary motions are horizontal
and much of the fault is further inland.
Land subsidence resulting from sediment compac-
tion and fluid (water, petroleum) withdrawal may cause
relative sea level to rise. Compaction is particularly
important in deltas and other coastal wetlands, where
sediments have high water contents. Withdrawal of
groundwater and petroleum increases the effective
stresses in the surrounding sediments, resulting in
consolidation and subsidence, which may be partially
reversed by returning fluids to the subsurface.
GEOGRAPHIC VARIATION ALONG THE
U.S. WEST COAST
How much coastal inundation can be expected
with sea-level rise depends on the local geomorphology,
which varies significantly along the west coast of the
United States. The geomorphologic features along
the coast are primarily the result of a collision between
the North American and Pacific plates that began more
than 100 million years ago and created steep coastal
mountains, uplifted marine terraces, and sea cliffs.
Over time, coastal lowlands developed, dominated
by long sandy beaches, estuaries, and other wetlands.
Most of the California coastline (72 percent or about
1,265 km) is characterized by steep, actively eroding sea
cliffs, including about 1,040 km of relatively low-relief
FIGURE 1.7 Response of the solid earth (brown) to the growth cliffs and bluffs, typically eroded into uplifted marine
and melting of an ice sheet (blue) at increasing distances from terraces (Figure 1.9), and 225 km of high-relief cliffs
the ice (A, B, and C). The addition of an ice sheet causes the and coastal mountains (Figure 1.10). The remain-
land below it to subside and pushes (red arrow) a peripheral
bulge outward. With deglaciation, the subsurface material flows
ing 28 percent of the coastline is relatively flat and
back toward the area formerly covered by ice until equilibrium comprises wide beaches, sand dunes, bays, estuaries,
is again reached. SOURCE: Modified from Kemp et al. (2011). lagoons, and wetlands.
The coast of Oregon is dominated by resistant
volcanic headlands separated by areas of lower relief.
Subduction Zone offshore Washington, Oregon, and The latter are characterized by uplifted marine ter-
northernmost California (Figure 1.8). In subduction races, valleys where rivers emerge at the shoreline, and
zones, strain builds within the fault zone, causing the associated estuaries, sand spits, beaches, and dunes.
land to rise slowly before subsiding abruptly during a The most extensive sand spits occur along the north-
great (magnitude greater than 8) earthquake. The last ern Oregon coastline. The longest continuous beach
great earthquake in the region occurred in 1700, caus- extends about 96 km, from Coos Bay to Heceta Head,
ing a sudden rise in relative sea level of up to 2 m due near Florence. The largest coastal dune complex in the
to subsidence (Atwater et al., 2005). Since that event, United States backs this region (Figure 1.11). Many
much of the coastline of northern California, Oregon, of the estuarine wetlands have been diked, primarily
and Washington has been slowly rising. Land motions to provide pasturelands.
18 SEA-LEVEL RISE FOR THE COASTS OF CALIFORNIA, OREGON, AND WASHINGTON
BOX 1.2
Changes in Relative Sea Level Along the U.S. West Coast Since the Last Glacial Maximum
During the last ice age, northern Washington was covered by the Laurentide Ice Sheet. When the ice sheet retreated, coastal areas that had been
depressed under the weight of the ice sheet were flooded. Relative sea level peaked in that area about 17,000 years ago, reaching values of about 90 m
above present in Anacotes (#1 in the Figure) and about 40 m above present in Seattle (#2). Subsequent glacio-isostatic uplift caused relative sea level
to fall to its lowest levels about 12,000 years ago (about -40 m in Anacortes and -55 m in Seattle). Relative sea level then rose as ice meltwater was
transferred to the oceans and the Laurentide Ice Sheet peripheral bulge began to collapse, causing coastal subsidence.
Glacio-isostatic contributions were much lower in southern Washington, Oregon, and northern California (#3#9 in the Figure) than for northern
Washington, but they were still a dominant influence on sea level. In this area, rates of relative sea-level rise slowed as the effects of glacio-isostatic
subsidence decreased. In Eureka, California (#7), for example, relative sea level rose at an average rate of about 7.5 mm yr-1 between 10,000 and 6,000
years before present, then rose at a decreasing rate.
1. Anacortes, WA
220
90
-40
2. Seattle, WA
40
-10
-60
3. Long Beach, WA
10
-45
-100
4. Pacific City, OR
10
-20
Relative Sea Level (meters)
-50 Index Point
5. Waldport, OR
10
Terrestrial Limiting
-20 Marine Limiting
-50 ICE-5G VM5a
6. Coos Bay, OR
10
ICE-6G VM5a
-20
-50
7. Eureka, CA
10
-20
-50
8. Sacramento/San Joaquin Valley, CA
10
-20
-50
9. South San Francisco Bay, CA
10
-20
-50
18 12 6 0
Age (ka)
FIGURE Reconstruction of changes in relative sea level over the past 18,000 years for nine locations in Washington, Oregon, and California. Green crosses
(index points) represent former sea levels inferred from dated organic sediment in salt and fresh water marshes. Limiting data are from marine shells
(blue crosses) and terrestrial peat (orange crosses) that must have been laid down below and above mean sea level, respectively. Red and black lines are
model predictions (Peltier and Drummond, 2008; Argus and Peltier, 2010; Peltier, 2010). SOURCE: Data provided by Richard Peltier, University of Toronto.
INTRODUCTION 19
FIGURE 1.8 Major tectonic features along the western United States. Subduction of the oceanic Juan de Fuca and Gorda plates
beneath the North American Plate occurs along the Cascadia Subduction Zone, which extends more than 1,000 km from Mendocino,
California, to Vancouver Island. South of Cape Mendocino, the North American and Pacific plates slide past one another along the
San Andreas Fault Zone. The land west of the San Andreas Fault, from San Diego to Cape Mendocino, is moving northwest relative
to the rest of North America. SOURCE: U.S. Geological Survey, .
The shoreline of southern Washington is domi- ORGANIZATION OF THE REPORT
nated by depositional landforms. Beaches, mostly
backed by dunes, some developed, extend northward This report evaluates changes in sea level in the
about 100 km from the mouth of the Columbia River global oceans and along the coasts of California,
to the mountainous Olympic Peninsula (Figure 1.12). Oregon, and Washington for 2030, 2050, and 2100.
The Long Beach Peninsula near the Columbia River Chapter 2 describes methods for measuring sea level
and Grays Harbor include some of the most extensive and presents recent estimates of global sea-level rise.
wetlands in Washington, outside of Puget Sound. Chapter 3 updates the IPCC (2007) estimates of the
Some of these wetlands are being restored (e.g., Fig- major components of global sea-level change--thermal
ure 1.13). Small coastal developments are present on expansion of ocean water, melting of glaciers and ice
portions of the peninsula and on the low-lying coastal sheets, and transfers of water between land reser-
areas to the north. voirs and the oceans. Chapter 4 assesses the factors
that influence sea-level change along the U.S. west
20 SEA-LEVEL RISE FOR THE COASTS OF CALIFORNIA, OREGON, AND WASHINGTON
FIGURE 1.9 Uplifted marine terraces, Santa Cruz County, California. SOURCE: Copyright 20022012 Kenneth & Gabrielle Adelman,
California Coastal Records Project, .
FIGURE 1.10 Steep rocky cliffs of the Marin Headlands north of San Francisco, California. SOURCE: Copyright 20022012 K
enneth
& Gabrielle Adelman, California Coastal Records P
roject, .
INTRODUCTION 21
FIGURE 1.11 Oregon Dunes National Recreation Area. The largest coastal dune field in the United States has developed along the
central Oregon coast and extends inland up to 3 km. SOURCE: Gary Griggs, University of California, Santa Cruz.
FIGURE 1.12 Long Beach Peninsula, Washington. Sandy beaches backed by dunes dominate the southern coast of Washington.
SOURCE: Courtesy of Phoebe Zarnetske, Oregon State University.
22 SEA-LEVEL RISE FOR THE COASTS OF CALIFORNIA, OREGON, AND WASHINGTON
FIGURE 1.13 Tidal wetlands along the mouth of the Nisqually River, Washington, are being restored following removal of a dike
built a century ago to drain the area for cattle ranching. SOURCE: Courtesy of Carl Safina; photo taken for the PBS television series
Saving the Ocean.
coast, including regional changes in ocean circulation, Hawaii, appears in Appendix D. Chapter 5 summarizes
climate-induced changes in storms, gravitational and
recent projections of global and regional sea-level rise
deformational effects of land ice change, and vertical and presents the committee's projections for 2030,
land motions. It also summarizes the results of the 2050, and 2100. The method used to project the cryo-
committee's analysis of tide gage and GPS records spheric component of global sea-level rise is described
from the California, Oregon, and Washington coasts, in Appendix E. Chapter 5 also describes what rare,
which is discussed in detail in Appendix A. Sea-level extreme events, such as a great earthquake along the
data from the northeast Pacific Ocean is presented in Cascadia Subduction Zone, might mean for local sea-
Appendix B. Data and uncertainties associated with level rise. Chapter 6 summarizes the literature on natu-
the analysis of gravitational and deformational effects ral shoreline responses to and protection from sea-level
of land ice change are given in Appendix C. The tide change. Biographical sketches of committee members
gage and vertical land motion analyses draw on leveling are given in Appendix F, and a list of acronyms and
data, and a description of leveling data compiled and abbreviations appears in Appendix G.
analyzed for California by James Foster, University of
