The Contribution of Alaska's GlaciersThe Contribution of Alaska's Glaciers to Global Sea Level Rise to Global Sea Level Rise

Keith Echelmeyer, William Harrison, Keith Echelmeyer, William Harrison, Craig Lingle, Martin Truffer, Anthony Craig Lingle, Martin Truffer, Anthony

Arendt, Virginia Valentine, Sandy Arendt, Virginia Valentine, Sandy ZirnheldZirnheld

University of Alaska FairbanksUniversity of Alaska Fairbanks

Outline

• IntroductionIntroduction• Measuring volume changesMeasuring volume changes• Alaskan glacier changesAlaskan glacier changes• Future changesFuture changes• Effects of glacier changesEffects of glacier changes

Glaciers in the Arctic

Total volume corresponds to ~8 m of sea level

Mike Fleming, USGS

Measuring changes: The traditional method

Laser altimetry system

Calculating volume changes

about 100 glacier measured(out of several thousand)

Regional volume change

Total volume change

• 3300 km3300 km33 since 1950s since 1950s• enough to cover state of Alaska in 7 enough to cover state of Alaska in 7 ft of waterft of water(or Texas in 15 ft)(or Texas in 15 ft)

Contribution to Rising Sea Level

Time Period

Volume Change

(km3 WE/yr)

(mm/yr Sea Level

EQ)

Early: 1950s to 1990s -46 7

0.13 0.02

Recent: 1990s to 2001 -88 28

0.24 0.08

Assessing future changes

• Use models to relate climate to current and Use models to relate climate to current and past mass balancepast mass balance• Derive sensitivity factors for glaciers in Derive sensitivity factors for glaciers in different climate regimes (see Arendt et al different climate regimes (see Arendt et al poster)poster)• These models only apply to current glacier These models only apply to current glacier geometrygeometry• Long term predictions need to take glacier Long term predictions need to take glacier dynamics into accountdynamics into account

Complications

• Glaciers with flow instabilities can show a Glaciers with flow instabilities can show a variety of complex behavior:variety of complex behavior:• Surging glaciersSurging glaciers• Tidewater glaciersTidewater glaciers

Austin Post, USGS

1964 1965

Surging glaciers

Surge:Surge:• no appreciable change in total massno appreciable change in total mass• complete reversal of geometrycomplete reversal of geometry• quasi periodic phenomenonquasi periodic phenomenon• not (or weakly) related to climatenot (or weakly) related to climate

Tidewater glacier cycle: Glacier Bay

120 km

Tidewater glaciers

Tidewater glacier cycle:Tidewater glacier cycle:

• very rapid retreat (decades)very rapid retreat (decades)

• slow advance (centuries or more)slow advance (centuries or more)

• not directly related to climatenot directly related to climate

Effects of volume change

• Sealevel rise: currently ~0.24 mm/a

• Coastal currents

Alaska Coastal Current

Effects of volume change

• Sealevel rise: currently ~0.24 mm/a

• Coastal currents

• Isostatic uplift

Larsen et al, 2003

Conclusions

• Alaska provides the biggest current glacial contribution to sea level rise• Assessing the reactions to future climate change requires regional mass balance models• Glacier dynamics can pose significant challenges for such an assessment

Thank you

Glacier changes

Glacier-wide Average Annual Thickness Change (m/yr)-3

-2

-1

0

1

1950s to early 1990searly 1990s to 2001

-8

-6

-4

-2

0

(source: IPCC 2001)

Variations of the Earth’s surface temperature: past 1000 years.

Fiord

Nunatak Fiord

Dennis Trabant, USGS

Russell

Hubbard

Glacier

Russell

Fiord

Yakutat Bay

Yakutat Airport

Nunatak Fiord

~1130

1790

~18601895

5 milesSituk River

Grand Pacific Glacier

Glacier trim line (~1000 m asl)

Example of modern tidewater glacier retreat:

Columbia Glacier