A time-lapse video tweeted by NASA Earth captures decades of movement in our planet’s cryosphere. Glaciologist and University of Alaska Fairbanks faculty member, Mark Fahnestock appears in the video, describing the changes and the significance of the data. According to Fahnestock, the images taken from space are a product of the Landsat Program, a joint NASA/USGS program, which uses satellites to create a record of Earth’s landscape. Landsat, whose first iteration launched in 1972, is the longest ongoing space-based record of its kind.
The nearly five-minute video provides a glimpse of the land record from Landsat. The time-lapse footage has a frenetic feel to it as the satellite imagery improves with each generation of technology. It shows decades of change in ice cover on glaciers, including the Alsek, Columbia, and Taku Glaciers. Fahnestock noted the changes seen in the Hubbard and Malaspina Glaciers in particular. He draws attention to the time-lapse video of the Hubbard Glacier, in which the glacier can be seen spreading into a neighboring river moving trees, other material, and altering the environment. Fahnestock calls the Malaspina Glacier a “large puddle of ice” and describes how the time-lapse of this glacier helped him understand the looping patterns in moraines, or materials deposited by a moving glacier.
He credits remote sensing with expanding the field of observation glaciology. Fahnestock explains that these time-lapse videos have given glaciologists a better understanding of changes in ice cover. Landsat has provided them with a long record of changes, which allows researchers to recognize long-term trends in ice cover fluctuations and separate the trends from shorter periods of warm or cold years. Satellite observations of glaciers are mentioned in the IPCC’s latest output, Special Report on the Ocean and Cryosphere in a Changing Climate, which further stresses the significance of this kind of data.
According to Fahnestock, these time-lapse videos provide a historical record of how quickly glaciers are melting or in some cases, where glaciers are thickening. These changes in ice cover are visible in the video by NASA Earth, even to the untrained eye. Fahnestock addresses criticism he has received from other researchers––that he watches the videos too quickly. He says, “I like to see the fluid nature of the ice. It lets you see the ice on the land as sort of this very active participant in what’s going on.”