Understanding the causes and future direction of the present rapid thinning of Jakobshavn Isbræ, Greenland

The calving front of Jakobshavn Isbræ retreated by 10 km within only five years. (click to enlarge)

Jakobshavn Isbrae is the fastest outlet glacier of the Greenland ice sheet. During the the last 10 years it has been thinning substantially. Coinciding with the surface drawdown was the retreat of the calving front by 10 km, and a doubling of flow speed to approximately 14 km/year.

We will extract a detailed quantitative flow history of this system from the GPS and theodolite measurements, satellite imagery, and aerial photography, spanning 20 years.  These measurements will be interpreted through finite element modeling efforts designed to address the three dimensional nature of the ice flow in this system, requiring a full solution of the mass, momentum and energy balance equations.

We will determine the role of ice dynamics in the thinning seen in this system, and therefore bracket the contributions of surface mass balance and basal melting; we will quantify the flow resistance provided by the rapidly disappearing floating tongue in this system, thus addressing connections to possible ocean forcing; and we will measure the ongoing changes in the velocity field in detail, so that modeling may more effectively limit the possible directions of the future evolution of this system. In addressing all of these goals with a coordinated field, remote sensing, and modeling effort, we will make progress toward the goal of understanding changes in the mass of the Earth's ice cover and the potential impact of those changes on sea level and society.

This project is conducted in close collaboration with a NASA-funded project.