Larsen C ice shelf rift grows

It looks like the Larsen C ice shelf will break off in West Antarctica soon (in the next few months) after a sudden extension of the rift by 18 km in December, leaving just 20km holding 5000 square kilometre shelf on.

93282005_rift_figure_narrow_jan2017_large

Larsen A broke off in 1995, and Larsen B broke off in 2002.

This is what happens to ice shelves over time. There is no way of knowing if the process is being sped up by climate change or not.

RNZ: Huge iceberg poised to break off Antarctica

A long-running rift in the Larson C ice shelf grew suddenly in December and now just 20km of ice is keeping the 5000 sq km piece from floating away.

…in December the speed of the rift went into overdrive, growing by a further 18km in just a couple of weeks. What will become a massive iceberg now hangs on to the shelf by a thread just 20km long.

“If it doesn’t go in the next few months, I’ll be amazed,” project leader Prof Adrian Luckman, from Swansea University, told BBC News.

While very interesting this isn’t abnormal.

NZ Antarctic Research Institute director Gary Wilson said this was a fairly normal process for ice shelves to carve off when they came into enough interaction with storm swells.

He said the questions would be whether it would cause warmer water to get further under the ice shelf, and whether it would allow the storm swells to break up further back.

Larsen C is about 350m thick and floats on the seas at the edge of West Antarctica, holding back the flow of glaciers that feed into it.

As it floats on the sea, the resulting iceberg from the shelf will not raise sea levels. But if the shelf breaks up even more, it could result in glaciers that flow off the land behind it to speed up their passage towards the ocean. This non-floating ice would have an impact on sea levels.

According to estimates, if all the ice that the Larsen C shelf currently holds back entered the sea, global waters would rise by 10cm.

That’s likely to be a long term thing, if it happens. Sea levels have risen since the last ice age.

post-glacial_sea_level

What has changed recently is the huge increase in population and the establishment of settlements in low lying areas.