SEA LEVEL CHANGE AND TRANSPORTATION PLANNING by Bob Dean University of Florida SEA LEVEL CHANGE AND TRANSPORTATION PLANNING by Bob Dean University of Florida

Questions to Address (1) What is the Long-term History of Sea Level Change? (2) Is Global Sea Level Currently Rising? If so, What is the Rate? (3) Is Global Sea Level Accelerating? If so, What is the Rate? (4) Prognosis for Future Sea Level Rise Rates. (5) Relevance to ransportation System Design

Questions to Address (The Engineering Response) (1) Incorporate Effect in Initial Design (2) Retrofit at Some Future Time An Afterthought: Possible Role of Sunspots on Global Climate Change

Relative Sea Level Rise: Definitions Relative Sea Level Rise (RSLR) = Global Sea Level Rise + Local Effects Global = Eustatic Local = Tectonic + Compaction + Post Glacial Rebound + Subsidence + …….

Components of Eustatic SLR (1)Thermal expansion of water (2) Alpine glaciers (3) Ice Sheets: Greenland, and Antartica

Sea Level Change Over the Last 500 Million Years

Sea Level Change Over the Last 1 Million Years

Sea Level Rise Over the Last 24,000 Years

Sea Level Rise Over the Last 8,000 Years

World Wide Distribution of Long- Term Tide Gages

Relative Sea Level Change Based on Tide Gage Data

RSL Change: Juneau, AK An Example of Post Glacial Rebound

RSL Change: Adak, AK Note Tectonic Effects

RSL Trends in Alaska StationTrend (mm/year)Period Of Analysis Adak Anchorage – 1999 Cordova – 1999 Juneau – 1999 Ketchikan – 1999 Kodiak – 1999 Nikiski Sand Point – 1999 Seldovia – 1999 Seward – 1999 Sitka – 1999 Skagway Unalaska – 1999 Valdez – 1999 Yakutat

Subsidence Subsidence can be substantial exceeding the eustatic component significantly Long Beach, CA: > 6 m due to hydrocarbon extraction Tokyo: 3.5 m due to water extraction Osaka: > 2 m due to water extraction Coastal Louisiana: Up to 1 m per century due to natural and anthropogenic causes

Subsidence Due to Natural and Human Causes

Production Rates and Bottom Hole Pressure Reduction. Valentine Oil Field, LA a) Production Rates of Oil, Gas and Water b) Reduction in Bottom Hole Pressure

Eustatic Sea Level Rise Estimates Sea Level Rise Rate (mm/yr) Years No. of Tide Stations Investigators Barnett Barnett Gornitz & Peltier & Trupin & Douglas, et al Unal &

Average Sea Level Rise Over the Last 120 Years

Is Global Sea Level Rising? Yes. Over the Past Century, the Rate Has Been Between 1 and 2 mm/year (I Like 1.2 mm/year). A Caveat: Most Tide Gages Are Located Near Areas of Ground Water Extraction. Effect on Gage Readings?

Is Sea Level Rise Accelerating? Rate of CO 2 Increase, Mauna Loa, HI

Average Global Temperature Change

Some Predictions and Considerations of Future Sea Level Rise, 1980’s

Sea Level Rise Projections (IPCC) Long-term Eustatic Rate

Is Sea Level Accelerating?

Long Term RSLR at Several Locations

IPCC Estimates of Future SLR Date of IPCC Prediction Time Period (Years) IPCC Sea Level Rise Ranges IPCC Mid Range Estimate to cm to 95 cm 50 cm to cm to 88 cm49 cm

Probabilities of Sea Level Rise: 2000 to 2200

Is Sea Level Accelerating? (1)There are Indications of Sea Level Acceleration Although They Are Weak and do not Appear to be Increasing (2)Probably Won’t Know About Anthropogenic Effects Definitively for 30 or More Years

Will Sea Level Rise Accelerate in the Future? Probably, However, the Timing and Rates are Extremely Uncertain As Support, the Predicted Rates of Acceleration Have Decreased Since 1984 When Some Early Predictions Started

Engineering Responses * Some Highways: Increase Protection as Need Becomes Apparent * Bridges and Other Infrastructure Less Suited for Retrofitting: Allow for RSLR in Original Design

Example/Discussion Coastal Highways * Base design on predictions of local RSLR * Usually, not readily retrofitted during design life * Flooding of special concern if evacuation route * If evacuation route, design for upper limit of probabilities

Example/Discussion Revetment Protecting a Coastal Highway * Several coastal engineering options for retrofitting during design life, including * Adding more and heavier armor units * Beach nourishment to reduce size of waves

Summary Sea level has changed over millions of years under natural forcing Current rates of eustatic sea level rise are between 1.2 to 2.0 mm/yr There is not consensus of an acceleration of eustatic sea level rise nor of the role of human activity Transportation and design should understand coastal engineering options for retrofitting during design life Transportation planning and design should include local relative sea level rise if critical to the performance

Possible Role of Sunspots in Eustatic Sea Level Rise

Solar Forcing and Glaciation Stages

Sunspot History: 1700 to 2006

Recent Sunspot Activity

Correlation Between Sunspot Numbers and Solar Flux

Yearly Sunspot Numbers: 1610 to 2000

Reconstructed Temperature: 0 to 2000 AD (Note “Little Ice Age” Period)

QUESTIONS?

Example of Acceleration Concerns of Sea Level Rates (1983)

Is Sea Level Rise Accelerating? Consider: and evaluate a and b from the data on the following slide. b is an acceleration term.

Is Sea Level Rise Accelerating? This leads to: Where Is the average of the time period over which is determined. Solving for a and b from the data yields very unrealistic results signifying that the data are not well conditioned for this purpose.

Engineering Response NRC Report (1984) “The Prognosis for Sea Level Rise Should Not be a Cause for Alarm or Complacency”

Measurement of Sea Level Change

Outline (1) Definitions (2) Discuss Magnitudes of Relative Sea Level Rise (3) Is the rate of sea level rise increasing (4) Engineering responses to sea level rise (NRC Report)

Examples of Subsidence Due to Ground Fluid Extraction LocationCause of SubsidenceCharacterization of Subsidence Terminal Island, CAHydrocarbon Extraction> 6 m Tokyo, JapanGround Water Extraction> 4 m Osaka, JapanGround Water Extraction> 2 m Coastal LouisianaNatural Compaction and Extraction of Hydrocarbons Up to 1 m/year