Satellites Detect Both Steady and Accelerated Ice Loss

A new study published in Geophysical Research Letters reports the findings of a pair of satellites that measure gravity to get a clearer picture of the continued ice mass loss in Greenland, the Gulf of Alaska, and the Canadian Arctic Archipelago. The study found accelerated ice loss in the Arctic, and steady loss in Alaska, which will have significant implications for sea level rise globally.

Depiction of the GRACE satellites. (Source: NASA Jet Propulsion Laboratory)
Depiction of the GRACE satellites. (Source: NASA Jet Propulsion Laboratory)

The researchers, Christopher Harig and Frederik J. Simmons, both of Princeton University, analyzed data from the two satellites, called the Gravity Recovery and Climate Experiment (GRACE), in order to not only find the current state of ice mass within glaciers and ice sheets, but the changes in mass since 2003.

GRACE’s dual satellites circle the Earth together, and minute fluctuations in their orbit serve as a basis for measuring the Earth’s gravitational field. The two are separated by approximately 137 miles, and as they fluctuate with the changing gravitational pull, the distance between the two varies slightly. (The two satellites are nicknamed Tom and Jerry, a reference to the cartoon cat and mouse.)

Coupling the differing distances with precise GPS locations, GRACE is able to provide a view of the Earth’s gravity with “unprecedented accuracy” as NASA says. This level of detail allows researchers to easily find even minute trends in mass changes.

GRACE is more commonly used over large areas, such as ice sheets, but in this research the authors studied areas “near the [lower] limit that can be resolved by GRACE data.” After thermal expansion, mountain glaciers and ice caps are the second highest contributor to sea level rise, making accurate and efficient study of the mass loss from smaller areas critical for future sea level projections.

The researchers found that the glacial ice on the north region of the Gulf of Alaska was decreasing at a faster rate than the south region. GRACE detected an unexpectedly large ice loss in 2009 which the authors attribute to a lowered albedo after the eruption of Mount Redoubt.

NASA image of Eureka Sound on Ellesmere Island. (Source: Stuart Rankin/Flickr)
NASA image of Eureka Sound on Ellesmere Island. (Source: Stuart Rankin/Flickr)

The Canadian Archipelago as a whole has been losing ice mass steadily. Within it, the Ellesmere Island region was stable in 2003, when the data was first collected, but mass loss has been accelerating since. In 2013, the researchers found that the mass loss within the Ellesmere Island region had dramatically accelerated, but has since continued closer to average. Baffin Island, the second area studied within the Archipelago, also saw significant ice loss but not at the same rate as Ellesmere.

Greenland saw “an order of a magnitude” more total volume ice loss than Baffin and Ellesmere. Partially due to its sheer size, ice loss there is significant; in the previous decade the largest land-based contributor to sea level rise has been Greenland.

As ice mass loss continues in these regions due to natural variability and climate change, it will be important to have accurate and localized data to better prepare for the corresponding sea level rise.  

Visual depiction of sea level rise. (Source: go_greener_oz/Flickr)
Visual depiction of sea level rise. (Source: go_greener_oz/Flickr)

“Worldwide, on the order of 500 million people could be directly impacted by rising sea level by the end of this century. The human impact is combined with a large financial impact as well. So regardless of where people live, I think the impacts of ice loss and sea level rise will be easily seen in the future,” co-author Christopher Harig said in an email to GlacierHub.

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