<
https://www.sciencealert.com/west-antarctica-glaciers-retreat-unstoppable-study-says-tipping-point-crossed>
"Pine Island glacier is one of the fastest flowing outlets of ice from the west
Antarctic ice sheet, draining an area three-quarters the size of the UK. In
recent decades, the glacier has been retreating rapidly and losing ice,
contributing more to global sea level rise than any other Antarctic glacier.
The speed of the glacier's retreat and the rate that is has been losing ice has
led to concerns about how stable the region is. Model results show that this
region of west Antarctica could collapse in the future. If it does, then it
could raise global mean sea level by several metres.
There have been periods of rapid global sea-level rise in the past (by 1cm–2cm
per year). This probably happened because glaciers were losing mass at an
accelerated rate. One of the key mechanisms responsible for this is known as
"marine ice sheet instability".
When glaciers, like those in west Antarctica, experience a small retreat due to
some change in the climate, they can continue retreating even if the change is
reversed. Essentially, the glacier gets pushed beyond a tipping point, whereby
it experiences rapid mass loss until it reaches a new state.
This kind of retreat is irreversible because the change in climate needed for
the glacier to recover its original position is much greater than what
initially caused it to retreat.
This instability mechanism is well understood in theory, and models show it
could happen in west Antarctica in the future. But until now there has been no
proof that it had happened in the past.
In a new study, we found that Pine Island Glacier experienced irreversible mass
loss and retreat, starting in the 1940s. Our model suggests that a temporary
increase in melting under its floating ice shelf was enough to push the glacier
past a tipping point.
This phase of accelerated retreat had finished by the 1990s. But, in a separate
study where we used the same model, we found that the glacier will cross future
tipping points unless global warming is kept within safe limits."
Via Rixty Dixet.
Cheers,
*** Xanni ***
--
mailto:xanni@xanadu.net Andrew Pam
http://xanadu.com.au/ Chief Scientist, Xanadu
https://glasswings.com.au/ Partner, Glass Wings
https://sericyb.com.au/ Manager, Serious Cybernetics
