300 Years of Thinning Antarctic Ice May be Part of Why Ice Shelves Collapse

Researchers created a 6,250 year record of glacial meltwater discharge to make their analysis.
Fabienne Lang

Nowadays there's regular news about how ice shelves in the Antarctic or the Arctic are melting at rapid rates, or calving off huge sections that float off into the cold ocean. A lot of the blame is pointed toward climate change.

However, a new study published on Thursday in Nature pointed out that Antarctic ice shelves have been thinning for some 300 years, and may have predisposed these icy sections to collapse more quickly. 


How did the researchers come to this theory?

The team of British Antarctic Survey researchers had to look past ice mass loss and what effects this is having on the ice shelves at the moment.

300 Years of Thinning Antarctic Ice May be Part of Why Ice Shelves Collapse
Ice cliffs of the Brunt Ice Shelf near Mobster creek in Antarctica. Source: British Antarctic Survey

So, the team led by William Dickens assembled a 6,250-year record of glacial meltwater discharge. They managed to do this by analyzing isotopes — oxygen variants — in single-celled algae that were preserved in the underwater sediment core at the northeastern tip of the Antarctic peninsula.

When you encounter lower isotope rates, this means there is a higher discharge of freshwater. 

What did the researchers discover?

The years following the year 1400 saw an increasing amount in glacial meltwater discharge, reaching their peak in 1706. 

Another period when the discharge was particularly high was after 1912. 

Ultimately, the findings of the research pointed out that the ice shelves in the region have been thinning for around 300 years. This, in turn, may predispose them to collapse more easily when global warming occurs, as it is happening now.

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What led to the thinning of the ice shelves in the first place?

The study authors believe that part of the reason for the thinning ice shelves is due to the Southern Annular Mode (SAM) — a climate driver that can influence rainfall and temperature rise in Australia.

300 Years of Thinning Antarctic Ice May be Part of Why Ice Shelves Collapse
The Weddell Gyre within the Weddell Sea. Source: Hannes Grobe/Wikipedia

The SAM then led to strong westerly winds, atmospheric warming, and ice shelf melting in the eastern Antarctic peninsula. At the same time, it also directed warmer water to the Weddell Gyre, which could have led to ice shelves melting from underwater.

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