Home https://server7.kproxy.com/servlet/redirect.srv/sruj/smyrwpoii/p2/ Science https://server7.kproxy.com/servlet/redirect.srv/sruj/smyrwpoii/p2/ Satellite imagery can help predict when volcanoes under water are erupting

Satellite imagery can help predict when volcanoes under water are erupting

It is notoriously difficult to predict volcanic eruptions. This is because volcanoes are largely unique, each with their own peculiarities and personalities: the lessons from studying one volcano may not apply directly to another. Fortunately, researchers are getting better at finding warning signs that they can apply widely. Some of the best known are increased seismic activity, rising temperatures, expanding magma pools and the release of gases. New research using satellite imagery now offers a new warning sign for underwater volcanoes: a change in ocean color.

The idea is simple: it has long been known that when volcanoes under water prepare to erupt, the gases and compounds they release affect the composition of the surrounding seawater. Iron-rich water, for example, looks yellowish or brown, while aluminum and silicon make the water white. The challenge has always been to systematically use this information to make useful predictions. It is not easy to measure these color changes accurately.

Yuji Sakuno, an associate professor at Hiroshima University, has been working on this issue. As an expert in remote sensing, his key tool in this endeavor is the Japan Space Agency̵

7;s Global Change Observation Mission – Climate (GCOM-C) satellite. GCOM-C observes the ocean every 2-3 days at 250 meters of resolution, giving Sakuno reliable data on changes in water color over time.

Combining GCOM-C images with information on eruptions from Himawari-8 (a geostationary weather satellite), Sakuno was able to notice changes in seawater color about a month before volcanic activity on Nishinoshima Island.

This image shows a sample of the (Fe + Al) / Si distribution as a volcanic activity index from 16 May to 25 June around Nishinoshima Island: (a) 16 – 23 May 2020, (b) 24 – 31. May 2020, (c) 1-8. June 2020, (d) 9 – 16 June 2020, (e) 17 – 24 June 2020, (f) 25 June – 2 July 2020. It is mapped using the equation ((Fe + Al) / Si) = 45.4 (x) -13.3 for SGLI (Second Generation Global Imager – an instrument on board GCOM-C) data. From this it can be seen that during this period the distribution increases on the northeastern part of the island, and then the discoloration gradually reaches the sea area around the island before disappearing. Nishinoshima Island is located approximately 1,000 km south of Tokyo, Japan. The original data used for this product are provided by JAXA’s JASMES (JAXA Satellite Monitoring for Environmental Studies). Credit: JAXA / Yuji Sakuno.

One of the breakthroughs that made this possible involved finding a way to measure color accurately despite the way sunlight can distort and play tricks with apparent watercolor. Sakuno looked at other areas of research to find a solution: previous work on hot spring water provided the necessary tools to counteract the distortions of the sun.

Sakuno has big plans for this technique: “In the future,” he said, “I would like to establish a system that can predict volcanic eruptions with greater accuracy in cooperation with the Japanese Aviation Agency (JAXA), Maritime Security Agency, which monitors submarine volcanoes and related research. ”

This image illustrates the colorimetric data for discolored seawater in four directions (north, east, south and west) around Nishinoshima Island in 2020. The study examined the color properties of the water to validate if the data obtained by SGLI accurately record the actual conditions of the discolored seawater. It recorded significant fluctuations in the distribution of chemicals on Nishinoshima Island, estimated from SGLI data, about a month, even before the volcano became active. Credit: Yuji Sakuno.

This research also underscores the value of Earth observation satellites. The vast majority of spacecraft launched into orbit are not used to study the universe, but rather are turned to look back at Earth. Space tasks like GCOM-C are designed to improve life here at home. Whether by enabling communication and GPS or helping us understand and track climate change or keeping us protected from dramatic events like volcanic eruptions, the world’s space infrastructure has very real value for all of us earthbound earthlings.

Learn more:

“To predict underwater volcanic eruptions, scientists look at images from space.” Hiroshima University

Sakuno, Y. “Experiments in estimating chemical composition related to submarine volcanic activity using discolored seawater color data obtained from GCOM-C SGLI. A case study of Nishinoshima Island, Japan, in 2020. ” Water.

Highlighted image credit: NOAA / National Science Foundation: Overheated molten lava from West Mata submarine volcano.

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