Comprehensive Study of Greenland’s Outlet Glacier Dynamics
12.02.2008 - Other
A comprehensive new study documents in detail the dynamics of parts of Greenland's ice sheet. The rapid thinning and velocity increase on major Greenland outlet glaciers during the last two decades may indicate that these glaciers have become unstable. Scientists wanted to assess whether these recent trends deviated from longer-term behaviour. Their study, published online in the Journal of Glaciology (PDF), focuses on Jakobshavn Isbrae, Greenland's fastest moving and largest glacier, measuring four miles wide.
These outlet glaciers are quite important because their response to climate change can occur much more rapidly than that of the interior ice, which means they can therefore contribute to short-term changes in sea level. Moreover, the rapid thinning of peripheral outlet glaciers could be the initiator of an increased discharge of interior ice. This would lead to potentially severe impacts on global sea level rise as more ice is discharged into the oceans.
Scientists used a wide variety of techniques, including field mapping, ground surveys, remote sensing, satellite imaging and the application of digital techniques in order to glean "hidden" data from historic aerial photographs that were taken as much as 60 years ago. They were able to reconstruct the history of the glacier and the changes in its dynamics since the Little Ice Age.
It's the first time such a glacier is studied in detail over such a long period of time. Classically, scientists have assessed changes in glaciers by observing mainly their front zone, where iceberg calving occurs. This time, scientists had the opportunity to build a more comprehensive record, including long-term time series of surface elevation, calving-front and ice-marginal positions and ice-velocity changes.
This new study shows that glaciers do not necessarily react to climate change as a single, monolithic entity. Two different parts of the same glacier do not necessarily behave in the same way. This goes to show that the models used currently don't usually include the complexity of nature involved in ice dynamics. This research will thus give ice sheet modelers more precise and detailed data.
