The North Atlantic is exposed to an invasion of icebergs

May 31. () –

A study published in Science has been a pioneer in comparing the melting rate of icebergs during Heinrich Events with current projections for the Greenland ice sheet.

In paleoclimatology, a series of episodes that occurred during the period of the last ice age and in which waves of icebergs broke off from the glaciers are known as Heinrich Events. invade the North Atlantic pushed by ocean currents.

Yuxin Zhou, a postdoctoral researcher in the Department of Earth Sciences at UC Santa Barbara, has found that the predicted ice outflow from Greenland under the ongoing global warming scenario “is on par with a mid-range Heinrich event.”

Zhou compared the speed of icebergs calving from the Greenland ice sheet to ice flow during the Heinrich Events, the last time the AMOC current (Atlantic meridional overturning circulation), which tempers the climate in Europe, collapsed. Western. He found that as the Greenland ice sheet retreats inland, the iceberg calving likely won’t last long enough to completely derail the Atlantic circulation. That said, increasing freshwater runoff and continued global warming They continue to be threats to the stability of circulation.

Zhou went back in history to study the most recent period in which the AMOC was severely weakened: between 68,000 and 16,000 years ago, during the last glacial period. During colder periods there is more water trapped in the ice sheets, creating a reservoir to quickly flood the ocean with fresh water in the form of icebergs or runoff. Scientists called these episodes Heinrich Events when they came from the Laurentian ice sheet.

“It doesn’t exist today. But it used to cover northern North America and was miles thick in New York City,” Zhou said it’s a statement.

Comparing these Heinrich events to the current melt in Greenland allowed Zhou to predict how current trends could change the AMOC in the future. Icebergs bring larger sediments to the sea than water or wind, a signal that geologist Hartmut Heinrich noticed in seafloor cores in the North Atlantic.

To estimate how much ice each event released, Heinrich analyzed the amount of thorium-230 found in these sediments. This radioactive element is formed from the decay of uranium found naturally in seawater. Unlike uranium, thorium does not dissolve well in water, so it precipitates into particles in the water column. Because thorium-230 is produced at a constant rate, increased sediment flux dilutes its concentration. Working in reverse: less thorium means more sediment falling, carried by more icebergs.

“This is surprising and people should be worried. But, and this is a big ‘but,’ during the Heinrich events, the AMOC was already moderately weakened before all the icebergs arrived,” he said. “On the other hand, the circulation is very vigorous at this time.” This difference in the initial state is cause for some relief.

Heinrich’s events also lasted between tens and hundreds of years. Instead, the industrial revolution only began in the late 18th century, and carbon emissions increased much later. “It is possible that we simply did not make serious enough mistakes during the time enough for the AMOC to have really broken down“Zhou commented.