Satellite Images Show Walruses Gathered on Coast Due to Sea Ice Loss
Pacific walruses are being forced to gather in huge numbers in coastal areas to rest because of shrinking amounts of sea ice, according to a study.
The groups of animals were big enough to be spotted from space using imagery collected from various satellites orbiting the Earth.
The study was carried out by two researchers from the U.S. Geological Survey Alaska Science Center and aimed to evaluate how satellite imagery could be used to monitor the animals.
They looked at different types of satellite imagery with a range of different pixel resolutions using archived data between 2018 and 2020.
They found that both optical and radar imagery with resolutions of around 10 meters were useful in detecting the presence of walrus groups as well as the size of these groups near Point Lay in Alaska.
Point Lay is located on the coast of the Chukchi Sea between the west coast of the U.S. and the east coast of Russia.
Troublingly, the researchers also said that the animals were using coastal gathering areas "more often and in larger numbers" between feeding sessions. Historically, sea ice would have provided a resting area closer to their feeding grounds.
"Since 2007, during most years, sea ice has retreated northward beyond the continental shelf in the late summer and autumn, leaving Pacific walruses with no ice on which to rest between foraging bouts," the study states.
The change in the distribution of sea ice has "resulted in larger numbers coming ashore for longer periods on both the U.S. and Russian coasts of the Chukchi Sea."
The study, titled Evaluation of Satellite Imagery for Monitoring Pacific Walruses at a Large Coastal Haulout, was published on October 23 in the journal Remote Sensing. Pictures can be found here and here.
According to data from the National Snow and Ice Data Center, the average extent of Arctic sea ice has been decreasing at a rate of around 10 percent every decade since the early 1980s. NASA puts the figure at closer to 13 percent.
The loss of sea ice is driven in part by something called ice-albedo feedback. White sea ice tends to reflect the vast majority of sunlight that hits it. The darker sea water, on the other hand, tends to absorb most of it.
This means that the more the ice melts, the more this effect is pronounced in a pattern that reinforces melting.
