Jun 03, 2023

Arctic could be ice

FRANCE: The Arctic Ocean's ice cap will disappear in summer as soon as the 2030s and a decade earlier than thought, no matter how aggressively humanity draws down the carbon pollution that drives global warming, scientists said Tuesday.

Even capping global warming at 1.5 degrees Celsius in line with the Paris climate treaty will not prevent the north pole's vast expanse of floating ice from melting away in September, they reported in Nature Communications.

"It is too late to still protect the Arctic summer sea ice as a landscape and as a habitat," co-author Dirk Notz, a professor at the University of Hamburg's Institute of Oceanography, told AFP.

"This will be the first major component of our climate system that we lose because of our emission of greenhouse gases."

Decreased ice cover has serious impacts over time on weather, people and ecosystems -- not just within the region, but globally.

"It can accelerate global warming by melting permafrost laden with greenhouse gases, and sea level rise by melting the Greenland ice sheet," lead author Seung-Ki Min, a researcher at Pohang University of Science and Technology in South Korea, told Agencies.

Greenland's kilometres-thick blanket of ice contains enough frozen water to lift oceans six metres.

By contrast, melting sea ice has no discernible impact on sea levels because the ice is already in ocean water, like ice cubes in a glass. But it does feed into a vicious circle of warming.

About 90 percent of the Sun's energy that hits white sea ice is reflected back into space.

But when sunlight hits dark, unfrozen ocean water instead, nearly the same amount of that energy is absorbed by the ocean and spread across the globe.

Both the North and South Pole regions have warmed by three degrees Celsius compared to late 19th-century levels, nearly three times the global average.

An ice-free September in the 2030s "is a decade faster than in recent projections of the Intergovernmental Panel on Climate Change (IPCC)", the UN's science advisory body, said Min.

In its landmark 2021 report, the IPCC forecast with "high confidence" that the Arctic Ocean would become virtually ice-free at least once by mid-century, and even then only under more extreme greenhouse gas emissions scenarios.

The new study -- which draws from observational data covering the period 1979-2019 to adjust the IPCC models -- finds that threshold will most likely be crossed in the 2040s.

Min and his colleagues also calculated that human activity was responsible for up to 90 percent of the ice cap's shrinking, with only minor impacts from natural factors such as solar and volcanic activity.

The record minimum sea ice extent in the Arctic -- 3.4 million square kilometres (1.3 million square miles) -- occurred in 2012, with the second- and third-lowest ice-covered areas in 2020 and 2019, respectively.

Scientists describe the Arctic Ocean as "ice-free" if the area covered by ice is less than one million square kilometres, about seven percent of the ocean's total area.

Sea ice in Antarctica, meanwhile, dropped to 1.92 million square kilometres in February -- the lowest level on record and almost one million square kilometres below the 1991-2020 mean.

Disappearance of sea ice will open up the dark Arctic ocean, which will absorb – rather than reflect – heat, causing global heating to escalate further. It will also upend the region's ecosystem, harming everything from algae to large animals such as seals and polar bears that need the sea ice for hunting.

"It's a terminal diagnosis and now we have to live with consequences," said Robbie Mallett, a sea ice expert at University College London Earth Sciences. "It's been quite emotional to think of a time by the end of my career when I will see an Arctic free of sea ice. It's been a shocking few years in Greenland with ice disappearing before our eyes. We are driving a whole environment to extinction."

The loss of Arctic sea ice is "not the only sign of growing cryosphere collapse", according to the State of the Cryosphere report, which has been released by a group of scientists at the start of the United Nations’ Cop27 climate talks in Egypt.

In just the past year, researchers have been astonished by the sight of rain at the summit of Greenland's enormous ice sheet for the first time on record, followed by rain, rather than snow, falling on east Antarctica in March amid startling heatwaves at both poles, with temperatures 40C (72F) above normal.

The report documents shell damage to crustaceans in the Arctic Ocean, a sign that the seawater is acidifying due to greenhouse gas emissions, the loss of 5% of glacier ice in the Alps over a single summer and a record low sea ice extent around Antartica, earlier this year.

A huge amount of sea level rise appears to be already locked in due to the rampant burning of fossil fuels, the report states, with sections of the west Antarctic ice sheet potentially collapsing even without any further emissions over the coming centuries, causing more than four metres of additional sea level rise. Greenland's ice loss has already committed around 30cm to sea level rise.

The UN recently warned there is "no credible pathway" to governments keeping temperatures below an agreed threshold of a 1.5C (2.7F) increase, with 2.5C (4.5F), or possibly more now likely by the end of the century. Such a scenario could raise sea levels by up to 20 metres, although over hundreds of years.