Melting icebergs fizz like soda, a sound nicknamed Bergie Seltzer
Glacier ice can be up to 10 percent trapped air, squeezed into bubbles as old snow compacts. When an iceberg melts, those bubbles burst one by one with a popping fizz. Scientists even listen to the noise to measure how fast bergs are disappearing.
An iceberg is a floating piece of freshwater ice over 15 metres long that has broken from a glacier or ice shelf. Smaller fragments are bergy bits, and the tiniest, under a metre high, are growlers. Since pure ice is about 920 kilograms per cubic metre and seawater about 1,025, typically around a tenth of the volume shows above the surface, and the hidden shape is hard to judge from what is visible. The English word partly translates the Dutch ijsberg, ice mountain.
Sizes can be staggering. Greenland's glaciers tend to shed jagged, irregular bergs, while Antarctic shelves release flat-topped tabular ones, the biggest of all. The USS Glacier reported one 335 by 97 kilometres west of Scott Island on 12 November 1956, the largest on record, and B-15 measured nearly 300 by 40 kilometres in 2000. In the North Atlantic, the icebreaker Eastwind logged a berg standing 168 metres above the sea in 1958, as tall as a 55-storey building. Colours range beyond white to blue, green, black and striped, shaped by algae, sediment and bubble-free ice.
Bergs are unstable. As they melt and crack, their centre of gravity shifts and they can roll over without warning. A large berg flipping against a glacier front can shove the whole glacier backward briefly, generating glacial earthquakes. Most melting is driven by ocean water rather than sunshine, and waves speed up breakage.
Before 1914 there was no formal system to track them. Wireless telegraphy existed but many older mariners distrusted it. In April 1912 the Titanic, billed as practically unsinkable and warned by radio about ice, struck an iceberg and around 1,500 people died. An international safety conference in London in November 1913 led within three months to the International Ice Patrol, monitoring the Grand Banks of Newfoundland. Today satellites supply more than 95 percent of the data used by the U.S. National Ice Center.
Source: Iceberg
