Publication on cause for major Antarctic sea ice decline

Recent PhD graduate Theo Spira’s 2nd PhD chapter has just been published in Nature Climate Change!

Between 2015 and 2017, Antarctic sea ice took a dramatic turn — plunging from record highs to record lows in just a couple of years. Climate models still can’t fully capture what caused such a rapid shift.

In Theo’s study, we analyzed around 110,000 ocean measurements from beneath the icy surface of the Southern Ocean to explore how ocean changes may have played a part.

Our results show a clear story unfolding below the surface:

For nearly a decade, from 2005 to 2015, a key cold layer known as Antarctic Winter Water gradually thinned. This weakened the barrier separating the chilly surface from the warmer waters below. As a result, that deep heat crept upward, quietly setting the stage for change.
Then, in 2015, unusually strong winds stirred the ocean, mixing warm water toward the surface and melting large areas of sea ice.
Since then, the link between sea ice, the sea surface, and deeper warm layers has strengthened — helping to sustain the lower sea ice levels we see today.

In short, the evidence points to a two-step process: a long-term ocean buildup followed by a short, powerful atmospheric trigger.

These findings highlight that what happens below the surface can have major consequences above it. There’s still plenty to learn — especially about cause and effect — but this work sheds new light on the ocean’s hidden role in Antarctica’s sudden sea ice decline.

Find the paper here (open access):

The findings also got some media attention: