Florida Sea Level Rise:Past, Present, and Future

George A. Maul, PhDDepartment of Marine and Environmental Systems

Florida Institute of Technology

Laser Day

November 19, 2014

Outline of the Talk

Eustatic Historical Sea Level Change Relative Sea Level (RSL) Change What is Happening Around Florida? Global Sea Level Change Today Projections of Future Sea Level Questions & (maybe…) Answers

Eustatic Sea Level Over Time

Global Sea Level last 24,000 years

Maximum rate of rise ~3 feet per century

18,000 ypp

Florida coast 20 and 10 kiloyears before the present

Ice Age Mammoth from Melbourne FL

What is Mean Sea Level?

Surveyors define it as the average of the hourly water heights at a tide gauge for 19 years.

Questions: What is a tide gauge? What tide gauge? Why 19 years? Which 19 years (epoch)?

Captain James Cook’s sea level mark in Tasmania

Measuring Relative Sea Level

Typical Tide Gauge Virginia Institute of Marine Science

Calculating Annual Mean Relative Sea Level

𝑀𝑆𝐿𝑦𝑒𝑎𝑟=∑1

8760 𝐻𝑜𝑢𝑟𝑙𝑦 h𝐻𝑒𝑖𝑔 𝑡h𝑜𝑢𝑟𝑠𝑝𝑒𝑟 𝑦𝑒𝑎𝑟

Key West sea level rose steadily during 1846-1992

Factors Affecting Relative Sea Level Change

 RSL = Height thermal expansion

+ Height land motion

+ Height glacial melt

+ Height ocean circulation

+ Height winds

+ Height barometric pressure

+ Height tides

+ Residual

We’ll examine each of these next

CORS

Thermal Expansion and Ice Sheet Contributions

Global estimates from NASA

Deep Ocean Thermal Expansion ≈+0.06

feet/century

Like Mathematics?

𝐿𝑖𝑛𝑒𝑎𝑟 𝐿𝑒𝑎𝑠𝑡−𝑆𝑞𝑢𝑎𝑟𝑒𝑠𝐸𝑞𝑢𝑎𝑡𝑖𝑜𝑛 :𝑦=𝑎𝑥+𝑏

to be a minimum𝜕𝜕𝑎∑ ¿¿

∑ 𝑥𝑦−𝑎∑ 𝑥2−𝑏∑ 𝑥=0𝑎𝑛𝑑∑ 𝑦−𝑎∑ 𝑥−𝑛𝑏=0

yy

x

Vertical Land Motion

VLM (ft/cen) Method Source

-0.16±0.52 CORS NASA, JPL

+0.12±0.60 GPS Sella et al.

-0.14±0.16 Tide Gauge Zervas et al.

+0.10±0.14 Models Maul&Martin

No statistically significant evidence of Florida VLM

Sella et al., 2007

1.65 ft/cen

Ocean Circulation(increased Florida Current geostrophic velocity vg = lower Florida sea level)

1990 1995 2000 2005 2010 2015 2020500

600

700

800

900

1000

1100

1200

1300

1400

1500

14.1693

19.1693

24.1693

29.1693

34.1693

39.1693

f(x) = − 0.0209997594154088 x + 74.050986171138R² = 0.00220953152536763

Florida Current Volume Transport

Year

mill

ions

of

cubi

c fe

et p

er s

econ

d

106

m3s

-1

𝑓 𝑣𝑔=𝑔∆h∆ 𝑥

~ 0.01 ft/century

Inverted Barometer Effect

1900 1920 1940 1960 1980 2000 202029.95

30.00

30.05

30.10

30.15

1014.11

1015.11

1016.11

1017.11

1018.11

1019.11

1020.11

Annual Average Sea Level PressureiCOADS 24-26°N, 80-82°W

Year (1913-2013)

SLP

(in

. H

g)

SLP

(m

b)

(decreasing atmospheric sea-level-pressure = rising sea level)

;

~ +0.03 ft/century

RSL Trends at Selected Florida Stations

Ensemble Average = 0.73±0.09 feet/century

Florida Vertical Land Movement

-0.02±0.15 feet/century

Station Longitude(°W)

Latitude(°N)

Trend (feet/century)

SE(feet/century)

Epoch N(years)

Cedar Key 83.03 29.14 0.53 ±0.06 1939-2012

61

Fernandina Beach 81.46 30.67 0.65 ±0.04 1898-2012

94

Key West 81.81 24.56 0.74 ±0.03 1913-2012

99

Mayport 81.43 30.39 0.77 ±0.06 1929-2000

71

Miami Beach 80.16 25.73 0.75 ±0.09 1932-1980

44

Pensacola 87.21 30.40 0.71 ±0.05 1924-2012

85

St. Petersburg 82.63 27.76 0.82 ±0.05 1947-2012

66

MEAN ± SD     0.73±0.09      

Global Sea Level Trendfrom satellite altimetry

global average trend1.02±0.13 feet/century

regional trends in sea level 1992-2012No evidence of Florida sea level falling 1992-

2012

Projections for Global Sea Level Rise

Maximum rate of rise during last

18000 years

IPCC projected sea level to 2100

NOAA projected sea level to 2100

3.3 feet

Projected effect of a 3 foot relative sea level rise on Florida

At the current rate of Florida sea level rise of 0.75 feet per century, this will take ~400 years.

Key West Sea Level Revisited

No Statistically Significant Evidence of Accelerated Sea Level Rise

1900 1920 1940 1960 1980 2000 2020-1.6

-1.4

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0

f(x) = 0.00750977224738412 x − 15.8335322785428R² = 0.889240375646381f(x) = 14.7330738580848 ln(x) − 112.799674879319R² = 0.889130344795913f(x) = 1.81846774057477E-06 x² + 0.000373080934125301 x − 8.83306447502973R² = 0.889274783460185

Key West Sea Level

Year

NA

VD

'88

Hei

gh

t (f

eet)

Summary

Sea Level Is Always Changing Complex Measurement Problem

Vertical Land Motion Thermal Expansion Glacial Melt

Projections NOAA, IPCC, others Key West – no acceleration

Advising Coastal Managers Applying Global Projections Locally Coastal Infrastructure Lifetime It is tough to make

predictions, especially about the future.