A chronic shortage of observations of the vast ocean surrounding Antarctica is hindering more accurate forecasts of the consequences of the climate crisis, a meeting of 300 scientists has concluded.
The Southern Ocean has an outsized influence on the Earth’s climate, absorbing masses of the extra heat and carbon dioxide caused by human activities.
But at a time when the region is undergoing dramatic changes, including record low levels of sea ice, the ocean resembled a “data desert”, the scientists said.
Some 300 scientists from 25 countries ended a week-long conference in Hobart on Friday organised by the Southern Ocean Observing System (Soos) – a major international science initiative working to co-ordinate and improve observations around Antarctica.
A concluding conference statement said the Southern Ocean was undergoing “critical changes” seen in record low levels of sea-ice, record high temperatures and “dramatic” shifts in penguin populations.
“The chronic lack of observations for the Southern Ocean challenges our ability to detect and assess the consequences of change,” the statement said.
The sea ice around Antarctica has been at its lowest levels on record for the past two southern hemisphere summers.
As the region approached the peak of winter this week, satellite data showed there was about 2.5m sq km less ice than the long term average. Scientists have said the dramatic loss of ice this winter is unprecedented.
“We were completely unprepared for this and it was entirely unexpected, and that’s due to a deficit in our observing system,” said Dr Andrew Meijers, an oceanographer at the British Antarctic Survey.
Global climate models struggled to reproduce changes in the Southern Ocean, he said, and that was down to a lack of data.
While satellites were good at recording how much ice was covering the ocean, there was very little known about the thickness of the ice or of changes beneath it.
“Global warming is really ocean warming, and the Southern Ocean controls the rate of melt of the Antarctic ice sheet, which is the single greatest uncertainty in projecting future sea level rise,” he said.
Antarctica’s ecosystems were strongly tied to the growth of phytoplankton and krill, which were themselves linked to the annual cycles of sea ice, Meijers said.
Antarctic scientists warned earlier this month the number of extreme events on and around the continent – from the loss of sea ice to melting ice sheets and heatwaves – would almost certainly get worse as the planet continued to warm.
Scientists found this year that a deep Antarctic ocean current that transports nutrients around the globe and influences the climate has slowed by about 30% since the 1990s. A separate study found the slowdown, blamed on increased melting of ice on Antarctica, was likely to intensify in coming decades.
Dr Sian Henley, co-chair of Soos and a marine scientist at the University of Edinburgh, said the Southern Ocean had a “disproportionate” role in the world’s climate system.
The world’s oceans have taken up about 90% of the extra heat being retained by the planet, caused mostly by humans burning fossil fuels and clearing forests. About 75% of that heat uptake happened in the Southern Ocean, Henley said.
Oceans also absorb about 30% of the extra CO2 from human activities, and about 40% of that ocean uptake takes place in the Southern Ocean.
Henley said: “If you look at the coverage of the global ocean, observations have increased. But the Southern Ocean is still a data desert. There’s a chronic shortage of data to address some of the most pressing questions.
“It’s now crystal clear that sea ice in the Antarctic is in peril and that puts its role in the climate system also under pressure.”
Also at the conference was Dr Ken Johnson, an ocean chemist at the Monterey Bay Aquarium Research Institute who leads a project deploying hundreds of ocean floats with sensors measuring temperature, salinity, oxygen levels, pH and nitrate levels.
“The Southern Ocean is the engine of the climate on Earth. At a time when we need to be measuring it more, we’re monitoring it less,” Johnson said.
He said the number of observations from sensors on board freight ships had been declining, and thousands of kilometres of ocean often went unmonitored, particularly through the southern hemisphere winter.