Scientists have gained new insight into what causes mysterious glacial earthquakes, potentially enabling scientists to build more accurate models of future climate change and sea-level rise.
At team of researchers combined field observations in Greenland with laboratory calving (the breaking off of ice from an iceberg into the ocean) experiments, the University of Michigan reported. The findings revealed that glaciers move rapidly backwards and downwards during calving events, causing the glacial quakes.
The Greenland ice sheet contributes significantly to the global sea level, and nearly half of its mass is lost through calving. glacial earthquakes have been observed to have increased seven-fold over only the past two decades and have been migrating northwards, suggesting ice loss from calving is also on the rise,
"Our new understanding is a crucial step toward developing tools to remotely measure the mass loss that occurs when icebergs break off ice sheets," said University of Michigan's L. Mac Cathles, an assistant professor in the Department of Earth and Environmental Sciences and the Department of Atmospheric, Oceanic and Space Sciences and a postdoctoral fellow in the Michigan Society of Fellows. "Combining field observations with laboratory measurements from scaled-model calving experiments provided insights into the dynamics of calving and glacial earthquakes that would not have otherwise been possible."
To make their findings, the researchers installed a "robust" wireless network of Global Positioning System devices on the surface of the2.4 mile-wide Helheim Glacier to measure its velocity and surface displacement. They combined these measurements with earthquake data from the Global Seismographic Network as well as scaled-down models conducted in water tanks.
"We were really surprised to see the glacier flowing backward in our GPS data. The motion happens every time a large iceberg is calved and a glacial earthquake is produced," said lead author Tavi Murray of Swansea University. "A theoretical model for the earthquakes and the laboratory experiments has allowed us to explain the backward and downward movement."
Understanding this behavior and how it is related to glacial earthquakes is expected to aid in remote measurements of calving events and how they contribute to sea-level rise. This could open the door for near-real-time estimates of iceberg loss.
The findings were published in a recent edition of the journal Science.