Melting arctic ice does not increase sea level. But it will still affect us

Melting arctic ice does not increase sea level. But it will still affect us

US government scientists said Monday that the floating ice cover in the Arctic Ocean Contraction to the second lowest degree Since satellite recording began in 1979.

Until this month, only once in the past 42 years, Earth’s frozen skull cap has covered less than 4 million square kilometers (1.5 million square miles).

The trend line is clear. Sea ice coverage decreased by 14% every 10 years. During that period.

The North Pole will see the first ice-free summer in 2035 as early as 2035. Researchers on nature weather change last month.

However, melted ice and snow do not directly raise sea level any more than a piece of melted ice makes a glass of water overflow. This raises awkward questions.

Of course, this would be bad news for polar bears already walking the runway towards extinction. Recent research.

And yes, it will definitely mean a significant change in the marine ecosystem of the region from phytoplankton to whales.

But if our core concern is the impact on humanity, we can legitimately ask, “So what?”

As it turns out, there are several reasons to worry about the knock-on consequences of declining Arctic sea ice.

Feedback loop

Scientists say, perhaps the most basic point is that the shrinking ice cap is not only a symptom of global warming, it is also a driver.

“The removal of sea ice exposes a dark sea that creates a powerful feedback mechanism,” said Marco Tedesco, geophysicist at Columbia University’s Earth Institute, told AFP.

Fresh snow It reflects 80% of the solar radiation. Back to space.

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However, when the mirror-like surface is replaced by deep blue water, approximately the same percentage of Earth’s heating energy is absorbed instead.

And we’re not talking about the stamp area here. The difference between the average ice cap from 1979 to 1990 and the lowest reported today (over 3 million km2) is twice that of France, Germany and Spain combined. .

The oceans have already absorbed 90% of the excess heat generated by man-made greenhouse gases, but at a terrible cost, including chemical changes, massive ocean heatwaves, and dying coral reefs.

And at some point, scientists warn that liquid heat sponges can simply become saturated.

Ocean current change

Earth’s complex climate system includes wind, tides and Heat salt circulation, It is driven by itself by changes in temperature (“heat”) and salt concentration (“harlin”).

Even small changes in this Great Ocean conveyor belt between the poles and across the three major oceans can have a huge impact on the climate.

For example, nearly 13,000 years ago, Earth’s temperature suddenly plummeted in Celsius capitals as Earth transitioned from an Ice Age to an interglacial period where our species could thrive.

They jumped again after about 1,000 years.

Geological evidence suggests that the slowing of the thermal saline cycle was partly caused by the enormous and rapid influx of cold, fresh water in the Arctic region.

Xavier Fettweis, a researcher at the University of Liège in Belgium, said, “The melting sea ice in Greenland and fresh water from grounded ice disrupts and weakens the Gulf Stream,” as part of a conveyor belt flowing through the Atlantic Ocean.

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“This is what allows Western Europe to have a milder climate compared to the same latitude in North America.”

Greenland’s huge ice sheet on land produced a net loss of over 5 trillion tons last year, all of which went into the sea.

Unlike sea ice, where sea level does not increase when it melts, the runoff from Greenland increases.

That record amount was partly due to warmer temperatures, which rose twice as fast in the Arctic than the entire Earth.

However, it was also caused by changes in weather patterns, especially an increase in sunny summer days.

Fettweis told AFP, “Some studies suggest that the increase in Arctic low-pressure conditions in the summer is partly due to the minimum sea ice range.”

Bear on thin ice

The current trajectory of climate change and the advent of ice-free summers, as defined by the UN’s IPCC Climate Science Panel as less than 1 million km2, will actually starve polar bears by the end of the century. nature.

“Global warming caused by humans means there is less and less sea ice for polar bears to hunt during the summer months,” said Steven Amstrup, lead author of the study and lead scientist at Polar Bears International, to AFP.

“The polar bear’s ultimate trajectory is to disappear without reducing greenhouse gas emissions.”

© Agence France-Presse

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