Home / Science / Melting of Arctic ice does not increase sea levels. But it will still affect us

Melting of Arctic ice does not increase sea levels. But it will still affect us



U.S. government researchers reported Monday that the Arctic Ocean’s floating ice cover has shrunk to its second lowest level since satellite registration began in 1979.

Up to this month, only once in the last 42 years, the Earth’s frozen skullcap has covered less than 4 million square kilometers (1.5 million square kilometers).

The trend line is clear: sea distribution has decreased by 14 percent per decade during that period.

The Arctic could see the first ice-free summer as early as 2035, researchers reported Nature’s climate change last month.

But all melting ice and snow does not directly raise the sea level more than melting ice cubes cause a glass of water to overflow, which gives rise to a difficult question: who cares?

Granted, this would be bad news for polar bears, which are already on a slippery slope towards extinction, according to a new study.

And yes, that would really mean a profound change in the region̵

7;s marine ecosystem, from phytoplankton to whales.

But if our end result is the effects on humanity, one can legitimately ask, “So what?”.

As it turns out, there are several reasons to be concerned about the consequences of the declining Arctic sea ice.

Feedback loops

Perhaps the most basic point to make, say researchers, is that a shrinking ice cap is not only a symptom of global warming, but also a driving force.

“Ocean removal exposes dark seas, creating a powerful feedback mechanism,” Marco Tedesco, a geophysicist at Columbia University’s Earth Institute, told AFP.

Newly fallen snow reflects 80 percent of the sun’s radiant power back into space.

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

And we are not talking about a stamp area here: the difference between the average ice cover minimum from 1979 to 1990 and the lowest point reported today – more than 3 million km2 – is twice as large as France, Germany and Spain combined.

The oceans are already tired of 90 percent of the excess heat generated by human greenhouse gases, but at a terrible cost, including changes in chemistry, massive marine heat waves and dying coral reefs.

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

Change ocean currents

The Earth’s complex climate system includes interconnected ocean currents driven by wind, tides and something called the thermohaline circulation, which in itself is driven by temperature changes (“thermo”) and salt concentration (“halin”).

Even small changes in this Great Ocean conveyor belt – which moves between the poles and across all three major oceans – can have a devastating climate impact.

Nearly 13,000 years ago, for example, when the earth transitioned from the ice age to the interglacial period that allowed our species to flourish, global temperatures suddenly plummeted several degrees Celsius.

They jumped up again about 1000 years later.

Geological evidence suggests that a slowdown in thermohaline circulation caused by a massive and rapid influx of cold, freshwater from the Arctic region was partly to blame.

“The fresh water from melting ice and grounded ice in Greenland disrupts and weakens the Gulf Stream”, part of the conveyor belt that flows in the Atlantic, says Xavier Fettweis, research assistant at the University of Liège in Belgium.

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

The massive ice on top of Greenland’s land mass saw a net loss of more than half a trillion tonnes last year, everything flowed into the sea.

Unlike sea ice, which does not increase sea level when it melts, runoff from Greenland does.

That record amount was partly due to warmer air temperatures, which have risen twice as fast in the Arctic as for the planet as a whole.

But it was also caused by a change in the weather pattern, especially an increase in sunny summer days.

“Some studies suggest that this increase in anticyclonic conditions in the Arctic during the summer is partly due to the minimal extent of sea ice,” Fettweis told AFP.

Bears on thin ice

The current path of climate change and the emergence of ice-free summers – defined by the UN’s IPCC climate panel as less than 1 million km2 – would indeed starve polar bears to extinction by the end of the century, according to a July study in Nature.

“The human cause of global warming is that polar bears have less and less sea ice to hunt during the summer months,” Steven Amstrup, lead author of the study and chief scientist for Polar Bears International, told AFP.

“The ultimate trajectory for polar bears with unreduced greenhouse gas emissions is disappearing.”

© Agence France-Presse


Source link