Antarctica is missing sea ice and scientists don’t know why
By Laura Chung
As the northern hemisphere swelters through endless heatwaves, scientists are turning their attention to the other side of the globe, where Antarctica is missing an Argentina-sized amount of sea ice. And scientists don’t know why.
CSIRO Fellow and Research Team Leader Dr Steve Rintoul said while there is some annual variation in ice coverage, this year’s records are the lowest in the 40 years since records started.
Antarctica’s sea ice has extended by a record low amount this winter, and scientists can’t explain why.Credit: Getty
As of mid-July, it was more than 2.6 million square kilometres below the 1981 to 2010 average – that’s an area nearly as large as Argentina, data from the National Snow and Ice Data Center (NSIDC) shows.
“It is stunning. The fact is we don’t know why [we’ve got record low sea ice]. No one predicted this, we don’t understand why this season is as low as it is,” he said.
Rintoul said sea ice forms when the surface of the ocean freezes. This layer of ice is thinnest at the end of February – during the continent’s summer – and builds back up in winter. But what controls how much ice is formed is a delicate interplay between the atmosphere and oceans.
“The factors that influence sea ice include winds from north to south are stronger than usual which pushes sea ice towards Antarctica and restricts how far sea ice spreads. The warmer water means there is less sea ice, and even things like melting the surface melt can alter sea ice forming,” he said.
Any of these factors – or a combination of them – could be driving the low sea ice coverage. But with less sea ice, oceans will absorb more heat, further warming oceans. This can have longer-term impacts on future sea ice cycles. With less sea ice, the atmosphere is also likely to warm up.
Together, this can have severe impacts on the ecosystems that rely on Antarctic sea ice – like the krill population which migrating whales rely on for food, or penguins who rely on sea ice for breeding.
Scientists have recorded significant decreases in sea ice around Antarctica since 2016. While there have been small rebounds in recent years, they remain far below the record high of 2014. The image below, from the University of Maine’s Climate Reanalyzer, compares sea ice extent in July 2014 to this month.
Australian Antarctic Program scientist and associate researcher at the University of Tasmania Dr Petra Heil said less sea ice would expose the Antarctic ice shelves to warmer water, resulting in greater melting and possible sea level rises.
“I am concerned by the rate of change in the last 18 months and I think it is hard to come back to our normal from there,” she said. “A major shift in Antarctica sea ice will – sooner rather than later – affect our global system. We need to be global citizens and step up to our duties and responsibilities.”
It comes as July is likely to be the hottest month ever recorded, and may be the hottest month in 120,000 years. This peak follows on from the warmest June on record.
The average temperature was about 1.5 degrees hotter than the planet was before it began to warm with greenhouse gas emissions during the industrial revolution.
The first three weeks of July were the warmest on record, with the global mean temperature temporarily exceeding the 1.5 degree threshold above the pre-industrial level during the first and third week of the month.
Early data shows this July looks set to be around 0.2 degrees warmer than the previous hottest July 2019, before Australia’s Black Summer bushfires, according to an analysis by Dr Karsten Haustein, a University of Leipzig scientist specialising in the attribution of extreme weather events to climate change.
As United Nations Secretary-General António Guterres said: “the era of global warming has ended ... the era of global boiling has arrived.”
“Climate change is here. It is terrifying. And it is just the beginning,” he said. “Children swept away by monsoon rains, families running from the flames (and) workers collapsing in scorching heat.”
On July 6, the global daily average temperature hit 17.2 degrees – the hottest ever recorded, surpassing the 17.18-degree record set just days earlier on July 4 and again on July 5, according to data from the University of Maine’s Climate Reanalyser. The previous record of 17.01 degrees was set on July 3.
Global average sea surface temperatures have also been warm since May, which has helped drive the warm temperatures. This has resulted in devastating coral bleaching off the coast of Florida, where scientists are racing to save what they can.
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