Antarctica is in the headlines again but for all the wrong reasons: a large section of the Larsen C ice shelf could break away, while meltwater lakes suggest that East Antarctica is melting faster than expected. Either event could affect the climate in all four corners of the world, writes Barbara Barkhausen in Sydney.
Just one year ago, scientists were painting a bleak picture of the future of Antarctica. Using satellite data and radar images, they discovered that the Larsen C ice shelf was thawing.
The neighbouring Larsen A and B ice shelves had already collapsed in 1995 and 2002, leading to the fairly certain conclusion that the third major ice shelf could also thin and become more fragile.
When will Larsen C collapse?
The reason is that temperatures in the Antarctic Peninsula have risen by 2.5 degrees Celsius over the past 50 years. The higher air temperatures shrink that ice shelf from above, while the warmer ocean currents do their part from below.
The Larsen ice shelf – which consists of three smaller ice shelves, Larsen A, B and C – is a long, fringing ice shelf along the east coast of the Antarctic Peninsula named after Captain Carl Anton Larsen, who led an expedition to the region in December 1893.
“If this vast ice shelf… was to collapse, it would allow the tributary glaciers behind it to flow faster into the sea. This would then contribute to sea-level rise,” warned Paul Holland of the British Antarctic Survey (BAS) last year, when he and his colleagues discovered a large crack in the Larsen ice shelf that was threatening its stability.
Crack has grown significantly and rapidly
Scientists have now discovered that the crack or rift has grown significantly and rapidly during the Antarctic polar night, when the prevailing darkness prevented satellites from observing it.
As of August 2016, the crack is now 22 kilometres longer than when satellites last observed it in March of this year. This is a rapid deterioration when you consider that it only grew by 30 kilometres in the four years between 2011 and 2015. In total, the crack is now 130 kilometres long.
“As this rift continues to extend, it will eventually cause a large section of the ice shelf to break away as an iceberg,” wrote the scientists from Project Midas, a UK-based Antarctic research project investigating the effects of global warming on the Larsen C ice shelf.
Computer modelling suggests that Larsen C could have the same fate as its neighbour Larsen B, which disintegrated in 2002 after a similar crack formed.
Lakes concern scientists
But the bad news doesn’t end there.
A recent satellite-based study from Durham University and Lancaster University in the UK uncovered a disturbing phenomenon in East Antarctica that is reminiscent of fast-melting Greenland: a large number of meltwater lakes have been forming during the summer months, just like its counterpart in the northern hemisphere.
Between 2000 and 2013, nearly 8,000 such lakes formed. And as in Greenland, these appear to drain down into the floating parts of the glacier, weakening it and making it more likely to break apart.
Global thermostat in danger
While scientists agree that these meltwater lakes are a clear sign of global warming, they still aren’t sure of their precise effect in and around Antarctica.
One Australian study using elephant seals could shed light on how melting ice changes oceanographic conditions. The elephant seals, which are indigenous to the region, were outfitted with tracking devices to gather and transmit information on the population and climate conditions in Antarctic waters.
So far the information has revealed that the water from the melting ice dilutes the denser water in the ocean depths. The scientists fear that further warming and increased ice melt could at some point alter the ocean’s currents.
With its cycles of freezing and thawing, the Antarctica regulates the world’s climate system. If the global thermostat breaks down, all of us will have cause to be concerned.