Dr Mike Williams from NIWA explains where the icebergs from Antarctica come from and how they were formed.
DR MIKE WILLIAMS
Icebergs come from either Antarctica or Greenland. Let’s talk about Antarctica: they’re made up of snow that’s fallen onto Antarctica. And then as more snow falls onto that, that squashes the first snow and as snow gets squashed it gets turned into ice. The weight of all that ice makes the ice on the bottom start flowing towards the coasts, and then once it goes off the coasts it becomes part of big ice shelves. And we’re talking really big: so for example the Ross ice shelf, which is the biggest ice shelf and the one that B15 came from, is roughly the size of France.
It spends several thousands of years going through that process of coming off Antarctica and into the ice shelves. And then we get fracture lines forming in the ice. These fractures start working the iceberg loose, and then they calve off the front. And icebergs calve in a whole variety of size, from small chunks the size of a car that pretty much disappear straight away, through to big icebergs like B15A which is as much as 200 kilometres long.
These big icebergs probably calve about once every 50 or 60 years. So it’s a very natural process, and -- and there’s, sort of, nothing alarming about a big iceberg calving.