The remote Pine Island Glacier in western Antarctica has been increasing speed in its descent toward the sea in recent years. Soon it will be depositing an iceberg as large as Dallas, Texas into the ocean. As it slowly melts, the sea level will rise a bit more. Cracks formed in the glacier in September or October of 2011.
A NASA research airplane discovered an 18 mile long crack on October 26, 2011. The fissure may be deep enough to reach all the way down to the ocean perhaps 200 feet below. The final break may be only months away.
How are Icebergs Formed?
Icebergs are not frozen lumps of ocean water. Ocean water can and does freeze, even though it freezes at a lower temperature than fresh water — 32 degrees F for fresh water vs. 28.4 F for sea water. Sea water can freeze to thicknesses that interfere with ship movements. In the coldest parts of the oceans frozen sea water can achieve thicknesses exceeding ten feet, challenging even the sturdiest ice breaking ships.
The North Pole is covered year-round with frozen sea water. The South Pole is a land mass — Antarctica — covered by a fresh water ice pack over three miles thick. Interestingly, there is a large fresh water lake at the bottom.
Icebergs are made of fresh water. As snow falls and packs down in regions of the earth where it doesn’t melt the snow becomes thick and packs tightly under its own weight forming glaciers. After centuries of snowfall glaciers can reach thicknesses of thousands of feet. The massive weight of the glacier transforms the snow to solid ice. The weight also causes heating by compression on the bottom of the glacier and melts the ice forming a surface for the glacier to slide across slowly — often just inches a day.
Glaciers that have a border on the ocean will creep into the water and break off when too much of the glacier extends outward. They may extend many miles over the water before breaking. These large extensions are called ice shelves, and exist only where temperatures are very cold for long periods of time — like the polar regions. The process of breaking — commonly called calving — is spectacular visually and the sound is unforgettable.
Large Icebergs are Nothing New
The concern about the Pine Island iceberg is not immediate. Icebergs many times larger occasionally drop into the sea. One 12,000 square mile chunk broke away in 1956. Another iceberg ingloriously named B15A, broke away in 2000 and required seven years to break up and melt. The real worry is that the Pine Island Glacier is receding — i.e., it seems to have stopped rebuilding itself to its original size before breaking off again.
Adding this much fresh water to the ocean might have harmful effects on marine life in the area. Also, Pine Island Glacier is huge, and if it continues to recede the amount of water added to the oceans could contribute to the worldwide rise in sea levels.
Frozen water in Antarctica is an important issue. The ice at the South Pole comprises 90% of the earth’s sea ice and 70% of the fresh water. If the ice on Antarctica melted, the sea would rise 60 feet worldwide, but such catastrophic melting is not expected.
The Pine Island Glacier is an isolated part of Antarctica. A NASA research airplane recently discovered a long and widening crack in the glacier indicating that it will drop a 340 square mile iceberg into the sea. This could disturb marine life in the region, but long term concerns are that the glacier itself will continue to melt and add to already increasing rises in sea levels around the world.
Sources:
- ”Sea Level and Climate,” Poore, Richard Z., Williams, Richard S. Jr., Tracey, Christopher. September, 2011. (Accessed: November 4, 2011)
- “Massive New Iceberg Forming -- Right now -- in Antarctica,” Netburn, Deborah. November 4, 2011 (Accessed: November 5, 2011)
Harvey Craft - I am a retired educator with diverse experience. I read anything science, education, and history. I write to share what I learn.
