Rob LarterAug 29, 2023
A thread about the extreme anomaly in Antarctic sea-ice extent this year, the present state of knowledge on the reasons for it and why further research is important.
I find the sharp downward trend in Antarctic sea-ice extent that started 7 years ago deeply unsettling, which is why I toot about it a lot.
1/n
Show threadRob Larter
The strength of arguments for climate action depends on solid scientific understanding, and at this point we don't have that for understanding the changes that have been observed in Antarctic sea-ice extent since satellite records of it began.
Inferences that a once in 100,000 year, or whatever period, event is unfolding based on standard deviations from a record that only extends over 45 years are not secure.
2/n
Aug 29, 2023 at 9:59pmWeb
Show threadRob LarterAug 29, 2023
We certainly can't make predictions about future change in Antarctic sea-ice extent with any great confidence when current understanding of the mechanisms controlling it is so poor.
To be credible, any theories proposing to explain the sharp decline in extent over the past 7 years also need to be able to account for the gradual increase in extent over the previous 38 years.
3/n
Show threadRob LarterAug 29, 2023
There is presently no scientific consensus on a theory that explains all the changes observed over the duration of the satellite record.
The situation is a lot more complex than in the Arctic because around the Antarctic winter sea ice growth extends into the open ocean rather than an enclosed basin.
4/n
Show threadRob LarterAug 29, 2023
The complexity is made greater by the fact that the Southern Ocean is home to the most powerful current on Earth, which is driven by the strong band of southern westerly winds. To understand what's happening to sea ice we need to understand the ocean and atmosphere as well.
5/n
Show threadRob LarterAug 29, 2023
Given that a solid explanation for the changes we're seeing is lacking there is an urgent need for a lot more research. Current spending on Antarctic and Southern Ocean research across all countries is a pittance compared to the costs of adaptation plans the results inform.
6/7
Show threadRob LarterAug 29, 2023
So in summary, be very concerned about the changes currently being observed. In parallel with lobbying for action though, lobby for more research, because we need that to strengthen the foundations of calls for action and to inform decisions on adaptation.
7/7
Show threadAndrew DonkinAug 30, 2023
@PoLaRobs Thanks for this thread explaining that.