About 12,000 years ago, during the last regional deglaciation in Antarctica, ice was moving much faster than it is today, according to a study led by the Polar Research Institute at the University of Cambridge .
To arrive at these results, the researchers analyzed the pattern followed by a series of wavy ridges detected on the Antarctic seafloor. These ridges occurred in places where the ice sheet, as a result of deglaciation , began to float, so that the ice pushed the sediment from the seabed as it moved up and down with the movement of the ice. tides.
“By examining landforms on the seafloor, we were able to determine how ice behaved in the past,” Julian Dowdeswell, lead author of this paper published in Science . “We knew these ridges were there, but never before have we been able to examine them in such detail.”
Underwater autonomous vehicles
How has it been possible to extract such precise information about an event that took place thousands of years ago? Modern satellites can only collect information on ice retreat and thinning rates over the past decades. To obtain high-resolution images of these ice-marked ridges, the scientists turned to an autonomous underwater vehicle, which is capable of operating at about 60 meters above the sea floor.
The analysis of the images, obtained in the Weddell Sea area, allowed the authors of the work to calculate the maximum speed at which the ice sheets can retreat, revealing that they are almost ten times faster than the maximum speeds observed today in day.
The researchers deduced that these small ridges were caused by ice moving up and down with the tides, compressing the sediment into well-preserved geological patterns – similar to the rungs of a ladder – as the ice retreated. Assuming a standard twelve-hour cycle between high and low tides, and measuring the distance between the ridges, the researchers were able to determine the speed at which the ice was retreating at the end of the last ice age.
Withdrawal of more than 10 kilometers per year
They calculated that during this period, the ice retreated between 40 and 50 meters per day, a rate that is equivalent to more than 10 kilometers per year. By comparison, modern satellite images show that even the fastest retreat lines currently known, for example on Pine Island, are much slower than these geological observations – just 1.6 kilometers per year.
“We now know that ice is capable of retreating at much higher speeds than we see today,” explains Dowdeswell. “If climate change continues to weaken ice shelves in the coming decades, we could see similar rates of retreat, with profound implications for global sea level. “
