Transcript 13 DAN cayan_OPC_sealevel_nov21 - CAL

OPC
Sacramento
11/29/2010
Sea Level Rise threat to California
Dan Cayan
Scripps Institution of Oceanography, UC San Diego
and USGS
Thanks to Reinhard Flick California Boating and Waterways
Sponsors:
California Energy Commission
NOAA RISA program
USGS CASCADE study
Observed SFO (left) and
modeled Global (right). Sea
level rise estimates based
upon an envelope of output
from several GHG emission
scenarios
Projected envelope of
global SLR (2009)
observed
Climate models only provide loose
guidance on the amount of sea level
rise—full physics models are still
under development.
But it is quite likely that rates
will increase greatly in future decades
San Francisco sea level and global estimated sea level rise
rise of sea level
along California
coast has followed
closely the
Estimated global
SLR rate
recent two decades
have not seen
Much rise along
California coast
however
highest hourly sea level on record
Extreme sea level occurrences
San Francisco
highest hourly
sea levels
have mainly
occurred in
just a few
years
San Francisco sea level and global estimated sea level rise
rise of sea level
along California
coast has followed
closely the
Estimated global
SLR rate
recent two decades
have not seen
Much rise along
California coast
however
The Satellite Data 1992-2009
Global MSL not evenly distributed
The “Keeling Curve”
385 ppm
Numbers fit if 57% of CO2
stays in atmosphere
San Francisco Yearly Mean Sea Level
315 ppm
Dave Keeling (1928-2005)
70 ppm (22%) increase in CO2 since 1957
Pre-industrial levels ~ 275 ppm
Improved Future Sea Level Rise Scenarios
60-140 cm MSLR
likely by 2100
SLR based on IPPC
GCM output
Cayan, D., M. Tyree, M. Dettinger, H. Hidalgo, T. Das, E. Maurer, P. Bromirski, N. Graham, and R. Flick,
Climate Change Scenarios and Sea Level Rise Estimates for California 2008 Climate Change Scenarios Assessment
Based on
Rahmstorf, 2007, A Semi-Empirical Approach to Projecting Future Sea-Level Rise, Science
Projected sea level
San Francisco
Under projected global
warming, such as in
the GFDL A2 simulation
sea level rises considerably
by 2100, in this scenario by
approximately 0.9m.
high sea level events,
exceeding high threshold
occur increasingly often and
persist for longer durations.
during high sea levels, the sea is often not quiescent
Winter 1983
sea level pressure
anomalous sea level
sea level anomalies
predicted sea level
observed sea level
sea level, observed
very high waves
during high sea level events
Wave height
significant wave height
Flick and Cayan 1980’s
San Francisco Bay/Delta
Water Levels
Coincidence of high sea level
and storms – major threat
~Jan 3 2006
Nasa
http://earthobservatory.nasa.gov/Newsroom/NewImages/Images
/ncalifflood_amo_2006004_lrg.jpg
Non-tidal
Range (floods)
Tidal range
Extreme water levels from San Francisco to Sacramento
Extreme elevations are the 99.99th percentile levels for 1993-2002, relative to the mean low river flow, from all data
within that span (may be different numbers of observations due to different recording gaps). Mean low river flow
reference levels were estimated as the mean of the all of the data from the low river flow period during 1991 and 1992.
SUMMARY
Sea level along the California coast has risen about 7” over the last 100yrs, nearly
same as global rate.
Global warming causes sea level rise (SLR) through two processes:
a) thermal expansion of the ocean, b) melting land ice adding water to global ocean.
Recent studies have predicted much higher sea level rise for the 21st Century than the
IPCC, exceeding 3 feet if greenhouse gas emissions continue to escalate
SLR causes inundation, but does not, by itself, cause beach erosion and flooding.
Run-up of big waves during high tides causes erosion and flooding. SLR worsens
effects of waves as time goes by.
Big storms, high tides and El Niño conditions will likely continue be the most potent
combination leading to coastal damage and erosion during the next few decades.
The key to understanding the coastal effects of future SLR is to measure the wavedriven beach and cliff erosion and flooding _today_ so we can construct data-based
models of shoreline retreat. What is needed is repeated LiDAR beach and cliff
retreat monitoring, along with wave data (CDIP) to connect the measured changes
with the waves.
Storm runoff will exacerbate high sea levels in estuaries—in particular the San
Francisco Bay/Delta
Reserve Slides
cm
mb
Figure 5. Projected total exceedences of San Francisco hourly sea level height (SLH) above
historical 99.99 percentile (black), and number that are coincident with sea level pressure
anomalies less than -7mb. Projected sea level from GFDL model weather and Nino3.4 SST
with a linear trend of 30cm over 2000-2100. (Cayan et al. In Review)
Projected sea levels
from the B1 and A2 emission
scenarios using the Rahmstorf
(2007) scheme for each of the
three models. Both the original
Rahmstorf (dashed curves) and a
version adjusted for the affect of
reservoirs and dams (solid) are
shown. Historical (blue) and
projected simulations (red shades)
are shown along with observed
global sea level (aqua).
Global Mean Sea Level Rise, recent history
125 cm/cy
20 cm/cy
1-2 cm/cy (till ~1800)
Start
De-glaciation
18,000 yrs ago
Global MSL has been ~constant during the rise of civilization
Climate change
projections
sustain(?)
present day
levels of
winter storminess
Winter 1983
sea level pressure
anomalous sea level
Sea level pressure
Sea level,
tide-removed
predicted sea level
tide prediction
observed sea level
Sea level, observed
Wave height
Wave Height
Flick and Cayan 1980’s
Sacramento+San Joaquin Flows during High San Francisco Sea Levels
simulated by Bay watershed model driven by GFDL A2 simulation
marked increase in number and intensity
Coincidence of storms and high tides in Winter 1983 -- heavy coastal damage
storms
Two high tides and two low
daily tides, unequal in
amplitude.
Monthly tidal changes
dominated by spring-neap
cycle, with two periods of
relatively high tides
(springs) around full and
new moon. One spring tide
range per month is usually
higher than the other on
this coast.
High tide levels vary by about 1 m
Highest storm-forced level = 28 cm
The highest monthly tides
in the winter and summer
months are higher than
those in the spring and fall
as a result of lunar and
solar declination effects.
Sacramento River water level is dominated by floods
Water levels, Sacramento I Street gage---floods!
Sacramento peak flows during the New Years 1997 storm were almost as large as the 1993 Mississippi peak flood flows
Orographic precipitation in Sierra Nevada:
Dettinger, M.D., et al. 2004: Winter orographic-precipitation ratios in the Sierra Nevada – large-scale atmospheric
circulations and hydrologic consequences. J. Hydrometeorology. 5(6), 1102–1116.
Atmospheric Circulation
during large low frequency
wave episodes is similar
for No Calif and Hawaii
This pattern must produce
long fetch, high westerlies
many of the same cases
that affect Hawaii also
affect No Calif
San Francisco & La Jolla Sea Level
4.0
San Francisco & La Jolla Annual Mean Sea Level
Feet (MLLW)
3.5
Trends 1927-2009
19 cm/cy SFO
cm/cy
21 cm/cy16
SIO
3.0
2.5
2.0
1850
1870
1890
1910
1930
1950
1970
NOAA hourly data available from SFO 1855-today; SIO 1927-today
1990
2010
Estimated sea level rise 2010
150
Vermeer/Rahmstorf semi-empirical scheme
Using several GCM simulated global temperature
100
cm
50
0
Coastal Impacts of Sea Level Rise and Storms
• Sea cliff retreat and beach erosion
• Storm surge related flooding
•Wave-induced structural damages
• Inundation of lowlands and coastal wetlands
• Saltwater intrusion into estuaries and freshwater aquifers
• Increased threat to San Francisco Bay/Delta levy system