Ellen Phiddian
Cosmos science journalist
Antarctic sea ice is at a record low for this time of year, according to the Australian Antarctic Program Partnership (AAPP).
It’s also the second winter in a row that sea ice is unusually low.
“In 2023, the winter extreme was outside everybody’s expectations – not just due to its sheer magnitude, but because it’s the wrong time of year. In winter the ocean should be freezing,” says Dr Will Hobbs, a sea ice researcher at the AAPP and the University of Tasmania.
“While the summer sea ice of 2024 was largely within the ‘normal’ variability, this winter we’ve again seen chaotic fluctuations similar to last year, now producing the lowest winter extreme on record.”
The AAPP uses satellite imagery to monitor Antarctic sea ice on a daily basis, alongside ocean voyages.
“At short time-scales – months to years – the atmosphere is the main driver of regional variability in Antarctic sea ice. What’s different now is that warmer Southern Ocean temperatures are really having an impact on the sea ice,” says Hobbs.
“The big question is whether that ocean warming is just a blip or is it related to climate change.
“Getting two such extreme events back-to-back is like throwing two double-sixes in a row – how many double-sixes do you need before you start thinking the dice are loaded?”
Antarctic sea ice typically peaks in September each year, at the end of winter.
On 7 September 2024, Antarctic ice covered 17.0 million square kilometres of ocean.
On average for this date, ice covers 18.4 million km2, and last year it covered 17.1 million km2.
“While it’s still too early to say whether winter sea ice has reached its maximum this year, it’s startling that the extent has dropped so low again – almost like the sea ice is being dissuaded from growing!” says Dr Phil Reid, who plots sea ice daily at the Bureau of Meteorology.
“We know that the past 2 years have been the warmest on record for the planet, with global temperatures more than 1.5°C above pre-industrial for extended periods. This global warmth is now reflected in the oceans around the Antarctic, and is likely a major factor in continuing record low sea ice,” says Hobbs.
Reid says that researchers don’t yet have a clear handle on how drops in Antarctic sea ice affect weather in Australia.
“For example, recent studies suggest that reduced sea-ice extent may lead to an increase in occurrence and duration of summer-time wet extremes over Australia, and, conversely, longer periods of dry days during winter,” he says.
“There are also key characteristics of sea ice that we can’t measure particularly well – like its thickness. It is possible that some of the sea ice being observed this year is quite thin, thinner than average, and vulnerable to atmospheric perturbations.”
With global warming causing rapid changes at the poles, Reid says more research is needed to understand these interactions.
The Ultramarine project – focussing on research and innovation in our marine environments – is supported by Minderoo Foundation.