Many impacts of climate change have been observed since the term drifted into common usage in the late 1970s and 80s. Although declining animal populations and statistics regarding rising sea levels and global temperatures have taken root in our daily lives and news cycles, many events in recent years have added stark, concrete images to the climate change discussion.
These tableaus range from out-of-the-ordinary polar bear migrations to the polar vortex aching its way across North America in early 2019. There has also been an increase in the discharge of icebergs from tidewater glaciers into Arctic waters by a process known as iceberg calving, and this has become a clear focus (and perhaps a cause for concern) for many scientists investigating the effects of climate change.
While the occurrence of iceberg calving clearly predates recent climate change, increases in calving from Greenland tidewater glaciers have been linked to warming of the adjacent ocean, while in other areas, like the Canadian Arctic, it seems that atmospheric warming (which is largely responsible for driving the retreat of glaciers that terminate on land) may also play a role.
Understanding exactly what is going on in any single location requires continuous monitoring of:
- the flow of the glacier,
- changes in the position and geometry of its terminus,
- local atmospheric and oceanographic conditions, and
- the location, timing, and style of iceberg production at each glacier.
Time-lapse photography is very well suited for monitoring iceberg calving, along with changing conditions on the glacier (like snow cover, surface melting, and glacier flow). It’s also suitable for exploring how factors like tidally induced changes in water level at the glacier terminus and the presence or absence of sea ice in front of the glacier might affect the calving process.
What is ice calving?
Iceberg calving, or glacier calving, is a process where sections of a glacier's ice cliff fracture and break off from the glacier and enter the fjord or ocean into which the glacier drains. The resulting icebergs are different from sea ice, which consists of frozen ocean water. The two often exist in close proximity to each other, however, especially in late winter when bergs calved earlier in the season may be trapped in the sea ice close to the glacier terminus, forming ice melange.
Because glacier flow continually transports ice towards a glacier's terminus, calving is a regular part of the life cycle of glaciers that end in the ocean. It begins with a rift or fracture opening in the glacier’s edge in response to the stresses that exist within the ice, and culminates with the fracture penetrating through enough of the glacier's thickness that bergs can break off.
A common stressor on glacier ice is the accumulation of meltwater in crevasses within the glacier. Because water is denser than ice, the meltwater that accumulates in the crevasses can stress the base of the crevasses enough to widen them through the full glacier thickness, triggering the calving of icebergs.
Calving in the Belcher Glacier
Although calving is a natural process for glaciers to shed mass, the rate at which this process occurs may be affected by such factors as rising air and ocean temperatures, changing sea levels, and changes in the degree to which sea ice may reinforce the terminal ice cliff.
The Belcher Glacier is one such glacier where ice calving has been observed by UAlberta scientists and others. It is a large tidewater glacier that drains the northeastern sector of the Devon Island Ice Cap in Nunavut, Canada. It calves icebergs into the ocean where the glacier terminates, which, in this case, is in Lady Ann Strait.
Stages of ice calving
The images of the Belcher Glacier above, captured over one summer by glaciologists Colleen Mortimer and Martin Sharp of the University of Alberta’s Department of Earth and Atmospheric Sciences, have also been rendered into a time-lapse video to better illustrate the process of glacier calving.
This time-lapse video is made using images collected by a solar-powered camera mounted on the valley wall to the east of the glacier terminus over a time-period from May (end of winter) to the following Fall. The camera's field of view is from east to west across the terminus, from which point the processes of calving could be easily observed for the entire summer season.