Transcript Storminess and Extreme Coastal Water Levels: Historical

Storminess and Extreme Coastal Water
Levels: Historical Observations and Future
Projections for the California Coast
Patrick Barnard
USGS Coastal and Marine Geology Program
Pacific Coastal and Marine Science Center, Santa Cruz, CA
Sea Level Rise
•Rate of global SLR has increased by
50% over last two decades
•West Coast sea level rise has been suppressed
for the last thirty years due to prevailing wind
patterns in the Eastern Pacific
•The global sea level rise signal is NOT
spatially uniform due to variations in
prevailing wind patterns, ocean
temperature and salinity (‘steric
effect’), and gravitational forces
Bromirski et al., JGR 2011
NOAA, 2011
•The current cold phase of the PDO may continue
to suppress sea levels for a decade or more
Coastal Water Level Factors for California
•Regional:
• Ocean circulation and wind
patterns
• Storminess*
• Tectonics (large-scale)
•Local:
• Subsidence
• Local tectonic deformation
• Fluvial discharge AND sediment
supply changes
Poland and Ireland, 1988
Subsidence in San Jose (1933-1969)
National Research Council study (due Summer 2012) will provide guidance
on West Coast SLR, including relative land movement, ocean circulation,
and storminess.
What is an extreme storm?
•Difficult to define
•Wave height/energy
•Wind speed/direction
•Atmospheric pressure
•Wave direction
•Storm duration
•Beach state
•Water level
•Largest waves = ~10 m (mean of
the highest 1/3, 1 in 100 = ~15 m)
•Elevated water levels
•Tide level (~2 m variation)
•Seasonal variations (up to ~30
cm)
•Surge (up to ~1 m)
•Wave set-up (up to ~1.7 m)
•Worst case = ~5 m static
water level increase on local
beaches
•Wave run-up can add an
additional 5 m!
Capitola, January 2008
Components of Total Water Level Predictions
breaker zone
swash zone
wave run-up
hR
wave set-up
hwv
wind set-up
hwn
barometric set-up
hDp
tide difference
htide
sea level rise
hslr
waves increase in height towards
breaking zone (shoaling)
H decreases rapidly due to
breaking
Hbr
dbr
MSL (datum)
(adapted from Frisby and Goldberg, 1981)
Bolinas Lagoon
Bathtub model (SLR + MHHW)
Physics included (SLR + Extreme Event)
Historical Trends in Storminess
•The frequency and intensity
of extreme storms in the
North Pacific increased over
the latter half of the 20th
century
•Trends of increased average summer,
winter and extreme wave energy for
much of U.S. West Coast
Allan and Komar, JCR 2006
Graham and Diaz, 2001
Changing El Niño Styles
Lee and McPhaden, GRL 2010
•
Two types of El Niños
– Classic/EP-El Niño
– El Niño Modoki/CP-El Niño
•
CP
EP
High sea levels tempered
during CP-El Niño but waves
equally powerful
CP-El Niño Intensity
•
The intensity of CP-El Niños
has increased over last three
decades- linked to global
climate change
•
California had extreme beach
erosion in 2009-10
EP-El Niño Intensity
Lee and McPhaden, GRL 2010
Future Projections for the CA Coast
•
Intergovernmental Panel on Climate
Change (IPCC) recently confirmed link
between climate change and frequency
of extreme storms
•
National Research Council study will
provide guidance on West Coast SLR
•
Most recent suite of climate models
show no clear trend in extreme events
for the CA coast
Assessing California’s Coastal Vulnerability
to Climate Change (SLR + Storms)
•
Process-based models that account for all aspects of future coastal
water levels, especially due to extreme storms
•
Models driven by output from the latest Climate Models, with
downscaled winds and pressure fields
•
Inclusion of regional and local sea level rise factors that affect
coastal vulnerability
•
State-wide, systematic approach to assess the impact of climate
change, including sea level rise AND storms
•
State-wide, comprehensive monitoring of waves, water levels and
coastal change
For more information, contact Patrick Barnard: [email protected]