Madrid, 27 years old (European press) –
Scientists described relaxing in the thick mass of floating icebergs on the boundary of the glacier in Jakobshavn Isbrae, Greenland, an hour before the outbreak of events.
This finding, from the Collaborative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado, may help scientists better understand future scenarios for sea level rise and it could also help them predict when major events will occur. The separation, also published in the journal Nature Geoscience.
Shortly before the tidal Jakobshavn Isbrae threw huge chunks of ice into the ocean, there is a sudden change in the group of icebergs that float along the end of the glacier, according to this new work, indicating relaxation in the thick mass of glaciers perched on Ocean glacial boundaries occur for up to an hour before penetration events.
In the winter months, icebergs and sea ice build up in the fjord in front of Jakobshavn Isbrae, forming an ice dam that prevents childbirth. The glacier could continue flowing into the fjord, untouched, advancing tens of meters every day.
The accumulation of ice material, which scientists call mixing ice, continues until summer, but its platform-like structure loses its rigidity with relative heat, and behaves like individual icebergs stuck in a fjord. To date, no studies have shown whether this type of late summer ice mix can affect the snowfall.
“It takes very little effort for the mixture to expand or relax a little, and then it stops being an ice jam,” says Ryan Kasuto, a researcher at CIRES ‘Center for Earth Observation and Science and lead author of the new study.
To understand what was happening during these disengagement events, Kasuto and colleagues brought ground-based radar interferometers to Greenland in 2012 and installed them in the icy fjord of Jakobchafen Isbra to record iceberg interactions every three minutes. They found that between landslides, icebergs moved in an ice mix together, flowing across the fjord as a cohesive unit.
But the movement of the individual icebergs changed before each of the 14 displacement events they observed: instead of flowing as a single coherent unit, the mix of ice relaxed and the icebergs began to move independently of one another.
“When the ice mixture relaxes, the individual icebergs start to rotate, and when they start to rotate, the mixture loses its structure. And when it loses its structure, it loses its ability to prevent separation,” Kasuto explains.
To understand what happens to icebergs within the ice mix during these events, the researchers used a particle dynamics model that simulates the movement of individual icebergs. They found that only a small downward expansion of the ice mix was necessary to trigger independent movement of the icebergs.
“As a gateway to the ocean, mixing of ice can have a direct effect on future projections of rising levels of seals,” said Justin Burton, assistant professor of physics at Emory University and co-author of the paper. It provided the best and most accurate data that clarifies the processes that lead to major breach events. This helps us understand the forces that determine how much ice is thrown into the ocean and how quickly it is produced. “
The exact cause of these shifts is not yet clear, but changes in ocean tides, meltwater discharges under the ice, and winds may help explain the sudden relaxation of the thick gathering of glaciers heading towards the glacier.
According to Cassuto, this study is the first to show that a mixture of ice-free sea ice can control the timing of separation. It is also the first study in which researchers have been able to observe the granular changes of matter within the natural environment.
“Most of the studies on granular materials are done in the labs,” recalls Jason Amundson, associate professor of geophysics at Southeastern University of Alaska and co-author of the work. These observations show that we can gain new insights into the behavior of materials. Study dense bundles of icebergs, which are some of the largest granular materials on Earth. “