Antarctic sea ice sinks to new winter low

September 11 () –

For the second winter in a row, Antarctic sea ice extent has been exceptionally below average and has just set a new record low for this time of year.

On September 7th, Sea ice extent reached only 17.0 million square kilometers, compared to the lowest extent in the previous winter on the same day in 2023 of 17.1 million square kilometers. The long-term normal for this date is 18.4 million square kilometers.

Throughout 2024, scientists at the Australian Antarctic Program Partnership (AAPP) have been monitoring sea ice extent, after sea ice cover last year was at the lowest levels since satellite records began.

AAPP scientist Dr Will Hobbs, based at the University of Tasmania, said in a statement that the record seasonal minimum is a further indication that the sea ice system around Antarctica is changing to a new state.

“In 2023, the winter extreme exceeded everyone’s expectations, not only because of its sheer magnitude, but because it is the wrong time of year. In winter, the ocean should be frozen.”

“While summer 2024 sea ice was largely within ‘normal’ variability, this winter We have again seen chaotic fluctuations similar to last year, which are now producing the lowest winter extreme on record,” he said.

“On short time scales (months to years), the atmosphere is the main driver of regional variability in Antarctic sea ice. What is different now is that “Warmer temperatures in the Southern Ocean are really having an impact on sea ice.”

“The big question is whether this ocean warming is just an accident or is it related to climate change. Having two extreme events of this type in a row It’s like rolling two double sixes in a row.“How many double sixes do you need before you start thinking the dice are loaded?”

“We know that the past two years have been the warmest on record on the planet, with global temperatures more than 1.5°C above pre-industrial levels for extended periods. This global warming is now reflected in the oceans around Antarctica. and is likely a major factor in the continued record levels of sea ice” said Dr. Hobbs.

Every day, Dr. Phil Reid of the Bureau of Meteorology (an AAPP partner agency) plots satellite data from the U.S. National Snow and Ice Data Center (NSIDC) at the University of Colorado.

“While it is still too early to say whether winter sea ice has peaked this year, it is surprising that the extent has dropped so much again, almost as if the sea ice is being deterred from growing,” Dr Reid said.

On September 7, sea ice extent reached just 17.0 million square kilometers, compared to the lowest extent in the previous winter on the same day in 2023 of 17.1 million square kilometers. The long-term normal for this date is 18.4 million square kilometers.

“We are really just beginning to understand the effects on our weather and climate of regionally low sea ice cover, combined with much warmer than normal ocean temperatures.

“For example, recent studies suggest that reduced sea ice extent may lead to an increase in the occurrence and duration of summer wet extremes in Australia and, conversely, longer periods of dry days during winter.

“Interactions between the ocean and the atmosphere, induced by the loss of sea ice in Antarctica, are thought to be driving these changes.

“There are also key features of sea ice that we can’t measure with particular precision, such as its thickness. It’s possible that some of the sea ice seen this year is quite thin, thinner than average, and vulnerable to atmospheric disturbances.

“It’s a gap in our knowledge of our sea ice environment that we need to fill, because our polar environments are changing rapidly,” Dr Reid said.