The Contribution of Alaska's Glaciers to Global Sea Level Rise Keith Echelmeyer, William Harrison, Craig Lingle, Martin Truffer, Anthony Arendt, Virginia Valentine, Sandy Zirnheld University of Alaska Fairbanks

Outline Introduction Measuring volume changes Alaskan glacier changes Future changes Effects of glacier changes

Glaciers in the Arctic Total volume corresponds to ~8 m of sea level Greenland 1,64 Mio km2 Canadian Arctic 0.108 Mio km2 Alaska 0.09 Mio km2 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 km3 since 1950s enough to cover state of Alaska in 7 ft of water (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 past mass balance Derive sensitivity factors for glaciers in different climate regimes (see Arendt et al poster) These models only apply to current glacier geometry Long term predictions need to take glacier dynamics into account

Complications Glaciers with flow instabilities can show a variety of complex behavior: Surging glaciers Tidewater glaciers

1965 1964 Austin Post, USGS

Surging glaciers Surge: no appreciable change in total mass complete reversal of geometry quasi periodic phenomenon not (or weakly) related to climate

Tidewater glacier cycle: Glacier Bay 120 km

Tidewater glaciers Tidewater glacier cycle: very rapid retreat (decades) slow advance (centuries or more) not directly related to climate

Effects of volume change Sealevel rise: currently ~0.24 mm/a Coastal currents

Alaska Coastal Current Greenland 1,64 Mio km2 Canadian Arctic 0.108 Mio km2 Alaska 0.09 Mio km2

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

Variations of the Earth’s surface temperature: past 1000 years. (source: IPCC 2001)

1895 ~1860 1790 Situk River ~1130 Yakutat Airport 5 miles Hubbard Glacier 1895 ~1860 1790 Russell Nunatak Russell Nunatak Fiord Fiord Fiord Fiord Yakutat Bay Situk River ~1130 Yakutat Airport 5 miles Dennis Trabant, USGS

Grand Pacific Glacier Glacier trim line (~1000 m asl)

Example of modern tidewater glacier retreat: Columbia Glacier