In recent years, glaciers near the North and South poles, as well as in mountainous areas, have been shrinking due to the effect of global warming, becoming a significant contributor to the recent sea level rise.
In recent years, glaciers near the North and South poles, as well as in mountainous areas, have been shrinking due to the effect of global warming, becoming a significant contributor to the recent sea level rise. Calving glaciers, which discharge icebergs into an ocean or lake, have retreated more rapidly than those on land because of sections collapsing at the glacier front and due to submarine melting.
It is, however, difficult to directly measure the volume of calving ice and submarine melting because conducting on-site examinations at the glacier front can be dangerous. Conventional methods that measure their volume based on satellite image analysis also yield only low temporal and spatial resolutions and do not allow continuous monitoring.
When icebergs break off into water, the so-called impulse waves or simply, tsunami waves, move over the ocean or lake. In this study, the team including Evgeny Podolskiy and Shin Sugiyama of Hokkaido University and Masahiro Minowa of the Austral University of Chile measured the volume of icebergs that broke off from Bowdoin Glacier, a calving glacier terminating at the head of Bowdoin Fjord. An underwater pressure sensor capable of making 20 measurements per second was placed in front of the glacier to record calving-generated tsunami waves measuring 10 centimeters to 1 meter high. The researchers then compared the data with high-resolution images of the glacier front taken by unmanned aerial vehicles (UAVs) as well as images by a time-lapse camera to find the relationship between calving events and tsunami-wave properties.
Read more at Hokkaido University
Photo: The calving front of Bowdoin Glacier in northwestern Greenland, where icebergs are discharged and ice under the water melts. Photo taken by Shin Sugiyama in 2015.