SEA LEVEL CHANGE AND TRANSPORTATION PLANNING

byBob Dean

University of Florida

SEA LEVEL CHANGE AND TRANSPORTATION PLANNING

byBob 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 EffectsGlobal = EustaticLocal = 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, AKAn Example of Post Glacial Rebound

RSL Change: Adak, AKNote Tectonic Effects

RSL Trends in AlaskaStation Trend (mm/year) Period Of Analysis

Adak -2.63 1957 - 1999

Anchorage + 2.67 1972 – 1999

Cordova + 6.97 1964 – 1999

Juneau -12.69 1936 – 1999

Ketchikan - 0.11 1919 – 1999

Kodiak - 12.08 1975 – 1999

Nikiski - 10.71 1973 - 1999

Sand Point + 0.07 1972 – 1999

Seldovia - 9.03 1964 – 1999

Seward - 1.46 1964 – 1999

Sitka - 2.17 1938 – 1999

Skagway - 12.69 1936 - 1999

Unalaska - 6.44 1957 – 1999

Valdez - 0.34 1973 – 1999

Yakutat - 5.75 1940 - 1999

Subsidence

• Subsidence can be substantial exceeding the eustatic component significantlyLong Beach, CA: > 6 m due to hydrocarbon extractionTokyo: 3.5 m due to water extractionOsaka: > 2 m due to water extractionCoastal 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

1.43 1881-1980 152 Barnett2.27 1930-1980 152 Barnett1.2 1880-1982 130 Gornitz &2.4 1920-1970 40 Peltier &

1.75 1900-1979 84 Trupin & 1.8 1880-1980 21 Douglas, et al

1.62 1807-1988 213 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?R

ate

of C

O2 I

ncr

ease

, M

aun

a L

oa, H

I

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

1995 1990 to 2100

15 cm to 95 cm

50 cm

2001 1990 to 2100

8 cm to 88 cm 49 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/DiscussionCoastal 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/DiscussionRevetment 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

Su

nsp

ot H

isto

ry:

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.

dSa bt

dt

Is Sea Level Rise Accelerating?

This leads to: dSa bt

dt

Where t 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.

dS

dt

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

Location Cause of Subsidence Characterization of Subsidence

Terminal Island, CA Hydrocarbon Extraction > 6 m

Tokyo, Japan Ground Water Extraction > 4 m

Osaka, Japan Ground Water Extraction > 2 m

Coastal Louisiana Natural Compaction and Extraction of Hydrocarbons

Up to 1 m/year