Conical clues of volcanic activity speckle the Aleutian Islands, a chain that spans the meeting place of the Pacific Ring of Fire and the edge of the Arctic. (The chain also spans the U.S. state of Alaska and the Far Eastern Federal District of Russia.) Scientists are now turning to advanced satellite imagery and supercomputing to measure the scale of natural hazards like volcanic eruptions and landslides in the Aleutians and across the Arctic surface over time.
When Mount Okmok, Alaska, unexpectedly erupted in July 2008, satellite images informed scientists that a new, 200-meter cone had grown beneath the ashy plume. But scientists suspected that topographic changes didn’t stop with the eruption and its immediate aftermath.
For long-term monitoring of the eruption, Chunli Dai, a geoscientist and senior research associate at The Ohio State University, accessed an extensive collection of digital elevation models (DEMs) recently released by ArcticDEM, a joint initiative of the National Geospatial-Intelligence Agency and National Science Foundation. With ArcticDEM, satellite images from multiple angles are processed by the Blue Waters petascale supercomputer to provide elevation measures, producing high-resolution models of the Arctic surface.
Dai first utilized these models to measure variations in lava thickness and estimate the volume that erupted from Tolbachik volcano in Kamchatka, Russia, in work published in Geophysical Research Letters in 2017. The success of that research guided her current applications of ArcticDEM for terrain mapping.
Monitoring long-term changes in a volcanic landscape is important, said Dai. “Ashes easily can flow away by water and by rain and then cause dramatic changes after the eruption,” she said. “Using this data, we can even see these changes…so that’s pretty new.”
Creating time series algorithms with the ArcticDEM data set, Dai tracks elevation changes from natural events and demonstrates their potential for monitoring the Arctic region. Her work has already shown that erosion continues years after a volcanic event, providing first-of-their-kind measurements of posteruption changes to the landscape. Dai presented this research at AGU’s Fall Meeting.
Elevating Measurement Methods
“This is absolutely the best resolution DEM data we have,” said Hannah Dietterich, a research geophysicist at the U.S. Geological Survey’s Alaska Volcano Observatory not involved in the study. “Certainly, for volcanoes in Alaska, we are excited about this.”
Volcanic events have traditionally been measured by aerial surveys or drones, which are expensive and time-consuming methods for long-term study. Once a hazardous event occurs, Dietterich explained, the “before” shots in before-and-after image sets are often missing. Now, ArcticDEM measurements spanning over a decade can be utilized to better understand and monitor changes to the Arctic surface shortly following such events, as well as years later.
For example, the volcanic eruption at Okmok resulted in a sudden 200-meter elevation gain from the new cone’s formation but also showed continuing erosion rates along the cone flanks of up to 15 meters each year.
Landslides and Climate
For Dai, landslides provide an even more exciting application of ArcticDEM technology. Landslides are generally unmapped, she explained, whereas “we know the locations of volcanoes, so a lot of studies have been done.”
Mass redistribution maps for both the Karrat Fjord landslide in Greenland in 2017 and the Taan Fiord landslide in Alaska in 2015 show significant mass wasting captured by DEMs before and after the events.
“We’re hoping that our project with this new data program [will] provide a mass wasting inventory that’s really new to the community,” said Dai, “and people can use it, especially for seeing the connection to global warming.”
Climate change is associated with many landslides studied by Dai and her team, who focus on mass wasting caused by thawing permafrost. ArcticDEM is not currently intended for predictive modeling, but as more data are collected over time, patterns may emerge that could help inform future permafrost loss or coastal retreat in the Arctic, according to Dietterich. “It is the best available archive of data for when crises happen.”
Global climate trends indicate that Arctic environments will continue to change in the coming years. “If we can measure that, then we can get the linkage between global warming and its impact on the Arctic land,” said Dai.
—Lara Streiff (@laragstreiff), Science Communication Program Graduate Student, University of California, Santa Cruz