Global Sea Level Rise

Laury Miller

NOAA Lab for Satellite Altimetry

Why Measure Sea Level Rise?

Inundation Will Have a Catastrophic Impact

What’s Causing Global Warming?

Net Heat Input Causes Global Warming

Top of Atmosphere

Heat Incoming

Heat Outgoing

Where Does the Heat Go?

Net Heat Input to

Earth System

(Levitus et al., GRL, 2004)

84% -- Saved By The Oceans!

Amount of Heat Absorbed by Parts of Earth Climate System Over Past 40 Years

Church et al., 2004, 2006

Holgate and Woodworth, 20041.8 +/- 0.3 mm/yr (1960 to 2000)

Satellite altimetrySatellite altimetry

What is the most obvious consequence?Mean Sea Level Rise, 1870-2000: ~1.7 mm/yr,

with an increase in the rate of rise

Altimeter Record of Sea Level Rise Over Past 15 Years

Sea Level Rise From Topex & Jason-1: 1993-2007

•Sea Level Rise is spatially, highly non-uniform

GLOSS Tide Gauges

• Tide gauges are important, but primarily for altimeter calibration

Ice Melt

More Water, More Mass

Thermal Expansion, More Volume

Heat

What’s Causing Sea Level Rise?

Sea Level Rise

Sea Level Budget Changes With TimeCurrent Rate Nearly Twice the 20th Century Rate

Largely Due to Volume Changes

Volume

MassVolume

Total Mass

Total

1920 - 1990 1992 - 2003

0.5 mm/yr

1.8 mm/yr

1.3 mm/yr1.5 mm/yr

1.7 mm/yr

3.2 mm/yr

Sources of Ice Melt & Potential Impact on Sea Level

70 m

Antarctica

6 m

Greenland

0.7 m

Mountain Glaciers

The loss poses grave environmental dangers … but not Sea Level Rise … (Archimedes Principle)

Summer 1979

Summer 2003

Arctic Sea Ice Is Disappearing At Record Rate

Cryospheric sea-level rise: glaciers and ice sheets

Glaciers62

Greenland28

Antarctica10

Sea Level Rise (%) [Meier et al., 2007]100% = 1.8 mm a-1

Glaciers70

Greenland20

Antarctica10

Sea Level Rise (%) [IPCC, 2006]]100% = 1.28 mm a-1

Glaciers50

Greenland30

Antarctica20

Sea Level Rise (%) [latest GRACE data)]100% = 2.2 mm a-1

Konrad Steffen, Steve Nerem,CIRES, Univ. of Colorado

Ice Melt Contributions to Sea Level Rise: Glaciers & Ice Sheets

Mountain Glaciers Are Currently the Biggest Source, But Probably Not For Long.

Greenland Is a Growing Worry

Its ice sheets are flowing faster towards the ocean during summer.

Possibly due to surface melt water cascading down crevases and providing lubrication at the ice/rock interface.

How Is The Ocean Heat Distribution Measured?

Argo Profiler Array

Courtesy of Mathieu Belbeoch, Argo Information Center* ice-free oceans

Starting in 2000, Argo Attained Global Coverage of the Oceans* in Nov 2007

How accurate are the projections?IPCC projects sea level to rise ~30-80 cm by 2100

Reconstructed record from tide

gauges

Satellite altimetry

The additional land-ice uncertainty

Model projection

Rahmstorf et al., Science, 2007

Observed sea level is rising at the upper limit of IPCC TAR projection that includes a “land-ice uncertainty”

* 4th Assessment Report

Can We Close the Sea Level Budget?

Jason = +3.6 mm/yr

GRACE = +0.8 mm/yr

Argo = -0.5 mm/yr

Argo + GRACE = +0.6 mm/yr ?

Willis, Chambers & Nerem, JGR, 2008

Mass Sea Level

Volume Sea Level

Total Sea Level