Field Notes: The Polar Field Services Newsletter

Calving Glaciers

In the past 100 years, glacial retreat has resulted in the formation of many freshwater lakes into which tumble mini-icebergs from the glacier in a process known as calving. As the ice chunks break away from the glacier, they—along with surface melting—contribute to the overall loss of glacial mass. Given the relatively recent phenomenon of freshwater glacial calving (as compared with tidewater calving, where a glacier terminates into an ocean fjord), scientists don’t yet understand the dynamics of how calving speeds up the rate by which glaciers recede.

Aerial photo of the glacial terminus by Chris Larsen

Aerial photo of the Yakutat glacial terminus (Chris Larsen). Glaciologist Roman Motyka and a team are studying the dynamics of glacial calving in freshwater lakes.

Enter University of Alaska glaciologist Roman Motyka and his research team. Through an extensive, three-year, National Science Foundation-funded research project on Yakutat Glacier in southeastern Alaska, the team is investigating how much of this glacier’s ice is wasting away due to calving versus surface ice loss. According to maps and old photos, the small pond at the foot of Yukatat Glacier expanded from a tiny seminal lake in 1900 to its present seven-mile-long lake.

“Why are these particular glaciers wasting away so fast?” asked Motyka. “What are the dynamics on these ice-marginal lakes, and as the lakes grow, will there be an acceleration of wastage, or not?”

Martin Truffer drills into the glacier to install monitoring equipment.

Martin Truffer drills into the glacier to install monitoring equipment.

Motyka and his team spent two weeks in May installing extensive monitoring equipment on the glacier to collect data including:

  • Thinning rates through surface mass balance, laser profiling, and photogrammetry
  • Ice thickness and bed geometry by radio echo sounding (RES) and lake bathymetry
  • Ice velocity and strain rates by continuous and campaign-style GPS, and by remote-sensing techniques
  • Changes in terminus position by photogrammetry
  • The lake environment, including water level fluctuations and water temperature.

    Team member Barbara Truessel sets up one continuous GPS unit in May

    Team member Barbara Truessel sets up one continuous GPS unit in May.

 

Barbara Truessel and Andy the Heli Pilot at the Mass Balance site.

Barbara Truessel and Andy the helo pilot at the Mass Balance site.

The collected data will be used to develop a lake glacier calving “law” that can be incorporated into dynamical models of glacier flow. The team will compare their observational and modeling results with data from other glaciers around the world through international collaborations.

The team will head back out to the field in July.