Antarctic sea ice levels are declining faster than ever

Antarctic sea ice levels are declining faster than ever
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TL;DR: In addition to being the largest reservoir of Earth’s fresh water, the Antarctic region plays a vital role in the planet’s ecosystem and climate cycle through its sea ice packs. However, this year, sea ice levels haven’t rebounded as scientists had anticipated, and this could signify a critical “tipping point” leading to irreversible changes in the climate cycle.

The Anthropocene is here, and the planet may already be beyond the point where climate change can be effectively mitigated, ensuring a decent chance of survival for most of humankind. This, at least, is one potential interpretation of a phenomenon observed by scientists earlier this year when the sea ice formations around Antarctica failed to recover as they typically do during winter.

Antarctic sea ice, typically a few meters thick, forms when seawater freezes during winter and retreats in the summer. However, in 2023, researchers discovered that Antarctic sea ice failed to “substantially” return to usual winter levels. The amount of frozen seawater around the South Pole reached “all-time low” levels in 2016, 2017, and 2022, but 2023 marked an entirely unprecedented milestone.

According to physical oceanographer Edward Doddridge, labeling this new milestone as “unprecedented” is insufficient. He emphasized that it qualifies as “a five-sigma event,” meaning it is five standard deviations beyond the mean. Doddridge explained that, if nothing had changed, we would expect to witness a winter like this approximately “once every 7.5 million years.”

Sea ice plays an important part in keeping Earth’s climate balanced and, well, survivable for human beings and other living species, as it helps the planet regulate its temperature by reflecting part of the Sun’s energy back into space through a process known as ice-albedo feedback. Furthermore, the annual cycle of freezing and melting drives global water currents which transport nutrients throughout the oceans and keep entire ecosystems alive.

If there is no Antarctic sea ice anymore, the scientists warn, sunlight will be absorbed by the ocean and temperatures will rise even faster than they are currently. Entire habitats like penguin and seal colonies could die out, while the lifecycle of smaller yet important organisms like krill could be disrupted.

Scientists are trying to understand why sea ice formation around Antarctica has come to a virtual standstill this year. Two significant potential factors have emerged: natural phenomena or human-induced climate change. Doddridge suggests that the latter is likely to blame, and the current situation may worsen in the near future.

According to Doddridge, changes in sea temperature likely disrupted sea ice formation. However, sea ice physicist Petra Heil believes the phenomenon results from a combination of atmospheric changes and warmer seawaters. Heil emphasizes that the entire system is “strongly coupled,” and the root cause of the problem lies in human activity. The scientists caution that we might be heading towards a new state for our planet, which could be “quite concerning” for the sustainability of human conditions on Earth.

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