April 20, 2024

Antarctic Low-Ice Winter Should Only Happen Once Every 13 Billion Years

As the northern hemisphere suffers through a record-breaking summer like the proverbial bull in a china shop, something even more extreme is happening at the other end of the world. Despite being locked in near-constant darkness, the waters off Antarctica are struggling to form ice. The event is so extreme, unlike anything we’ve seen before, that scientists calculate it would only happen once every 13 billion years if the planet’s temperature were stable. For it to be even close to probable the world must be warming at an unprecedented rate.

Until the 1970s our knowledge of sea ice extent depended on ships visiting specific locations, resulting in patchy Arctic estimates and almost no Antarctic data. Since then, satellites have provided a reliable estimate of sea ice extent every day. The Arctic data show a clear pattern of decline over that time period, which is lost approx 13 percent per decade.

The waters around Antarctica, however, were a different story, a story that climate change deniers would love to point out, because until the last ten years there was no clear pattern to be seen. Lately, however, southern waters have been catching up in the very undesirable race to be the fastest to lose ice.

It’s winter in the south, so sea ice is rising, but nowhere near as fast as last year’s record low, let alone the norm.

Image credit: National Snow and Ice Data Center

Nothing, however, glaciologists have prepared for this year. Almost every day in July has broken the previous world record for warmest average temperature, but the size of the break looks punitive compared to what’s happening around the coast of Antarctica.

The graph below tells the story.

As you might have guessed, the red line is for the past seven months, while the others track the previous years. However, the scale is not in square kilometers of ice – instead, it measures standard deviations from the mean for each day of the year over a 30-year measurement period.

This means that a score of -2 would be expected to occur once every 20 years under conditions that will not change. It is not surprising, then, that over a sample of 34 years the line was crossed several times, sometimes briefly. For the first three months of the year, that was about where 2023 was as well, though that even set a record. Then things went haywire. We now have almost 2.5 million square kilometers less Antarctic sea ice than usual for this time of year, an area the size of Algeria, the largest country in Africa.

The four standard deviation lines, or a four sigma event as physicists call it, should be crossed once every 10,000 years on a chart like this. More often shows changing conditions.

The IS ABC they reported this year’s ice extent as a five sigma event, which would be expected once in 7.5 million years, but they were either using the data from weeks ago, or they didn’t highlight the story so they wouldn’t look ridiculous. As the chart shows, we are now at a value of -6.4. That, as retired Professor Eliot Jacobson noticedit should only happen once in every 13 billion years with a normal distribution in a continuous environment.

Of course the situation is anything but fixed. The world is getting warmer, which means we should expect more years of low sea ice. However, you’d be hard-pressed to find a scientist who predicted anything that low.

On land ice loss can reflect atmospheric warming, but it can also be a result of lower precipitation or even (in some places) volcanic activity. At sea it must be warmer waters, air, or both.

Dr Edward Doddridge from the Institute of Marine and Antarctic Studies told the ABC, “It’s not unprecedented to say strong enough.”

Ice reflects much more sunlight than open water. There is hardly any light to be seen at the moment, but if there is no recovery by spring, absorbed light will warm the Southern Ocean, causing a vicious spiral.

Currents affect sea ice, but sea ice also drives currents, bringing nutrients to the surface that drive the marine food chain. Krill, which includes everything from whales to penguins, depend on algae under the ice. A winter like this can be devastating for many species, although the effects can last for months.

A forum was held about the possible consequences of such a catastrophic collapse just three weeks ago.

Bad as the consequences of this event will be, the causes could be even more serious. It is difficult to find an event so far outside the norm, not only with static climate, but with the predictions of most climate models. Things could be deteriorating faster than those models could handle.

It will be a while before scientific publications catch on to what happened and fully explain it, but as the scientists show in the video: we can’t wait for that to happen.

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