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 OPC Sacramento 11/29/2010 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 observed Projected envelope of global SLR (2009) 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

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 San Francisco sea level and global estimated sea level rise

highest hourly sea level on record

Extreme sea level occurrences San Francisco highest hourly sea levels have mainly occurred in just a few years

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 San Francisco sea level and global estimated sea level rise

The Satellite Data Fast Rise No Rise Global MSL not evenly distributed

The “Keeling Curve” San Francisco Yearly Mean Sea Level Dave Keeling ( ) 70 ppm (22%) increase in CO 2 since 1957 Pre-industrial levels ~ 275 ppm 315 ppm 385 ppm Numbers fit if 57% of CO 2 stays in atmosphere

Improved Future Sea Level Rise Scenarios cm MSLR likely by 2100 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 SLR based on IPPC GCM output

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

sea level anomalies sea level, observed significant wave height Wave height observed sea level predicted sea level anomalous sea level sea level pressure Flick and Cayan 1980’s Winter 1983 very high waves during high sea level events

San Francisco Bay/Delta Water Levels ~Jan Nasa /ncalifflood_amo_ _lrg.jpg Coincidence of high sea level and storms – major threat

Extreme water levels from San Francisco to Sacramento Extreme elevations are the 99.99th percentile levels for , 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 Tidal range Non-tidal Range (floods)

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 21 st 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 wave- driven 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

Figure 5. Projected total exceedences of San Francisco hourly sea level height (SLH) above historical 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 (Cayan et al. In Review) cm mb

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).

1-2 cm/cy (till ~1800) Global MSL has been ~constant during the rise of civilization 20 cm/cy125 cm/cy Global Mean Sea Level Rise, recent history Start De-glaciation 18,000 yrs ago

Climate change projections sustain(?) present day levels of winter storminess

Sea level pressure Sea level, tide-removed tide prediction Sea level, observed Wave Height Wave height observed sea level predicted sea level anomalous sea level sea level pressure Flick and Cayan 1980’s Winter 1983

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 heavy coastal damage High tide levels vary by about 1 m Highest storm-forced level = 28 cm 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. 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. storms

Water levels, Sacramento I Street gage---floods! Sacramento River water level is dominated by 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 16 cm/cy NOAA hourly data available from SFO 1855-today; SIO 1927-today

cm Estimated sea level rise 2010 Vermeer/Rahmstorf semi-empirical scheme Using several GCM simulated global temperature

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