Montshire Minute: Iceberg!

Originally aired during the week of August 10, 1998

Monday

Icebergs wander the cold ocean waters near the poles pretty much unimpeded, drifting about at the whim of currents and winds. They are the biggest thing in the water. I mean, no one wants to mess with an iceberg! Ever since early mariners encountered these floating towers of ice, the general rule of thumb has been to steer clear. Still, there have been at least 200 recorded collisions with icebergs since the early 1700's. The most famous iceberg is the one that had a close encounter with the hull of the "unsinkable" Titanic in 1912. Ice has only about 10 percent of the strength of concrete, which in turn has just ten percent of the strength of steel. But the Titantic's hull was not made of solid steel--it was steel plated. The force of the impact caused the steel plates to bend, popping out rivets and letting water in, and then . . . well, you know the rest of the story.

Tuesday

Icebergs are made of frozen water, the technical term for this being: ice. More accurately, "bergs," as scientists call them, come from glaciers, which are like slow moving rivers of ice formed by thousands of years of snow that never melted. When the glacier reaches the sea in spring, waves, tides and warmer temperatures go to work on the ice mass. Soon, pieces break off and float away, amid much spectacular crashing and roaring. This event is called "calving." Each year a whole herd of icebergs, about 10,000 of them, are released by Greenland's west coast glaciers. Then these oversized ice-cubes begin to drift about at the whims of winds and currents. The argest Arctic iceberg to date, sighted near Baffin Island a centry ago, measured 7 miles long and about 3 and a half miles wide. The largest Antarctic iceberg was spotted in 1956 - it was about as big as Belgium! Now that's a serious ice cube.

Wednesday

In the Arctic, brand new icebergs born from the Greenland glaciers may eventually drift south along the coast of Labrador. It may take a while for the bergs to get that far, for they often get trapped in the frozen seas in Baffin Bay during their first winter. Some of the bergs may also become stranded in shallow water off Labrador where they melt away during the summer. Icebergs that manage to avoid the shallows drift south between Greenland and the North American mainland (an area dubbed Iceberg Alley) before finding their way into the northern Atlantic Ocean. Of the 10,000 or so icebergs that start their journey in Greenland each year, only a few hundred make it past Newfoundland and into the open seas. On average, the "life expectancy" of glaciers that make it this far is about two years.

Thursday

By the time an iceberg reaches the waters near Newfoundland, it has probably lost 90 percent of its mass through melting. Yet large icebergs - like the 60-foot berg that sunk the Titanic - can still travel long distances. Bergs have been spotted as far south as 40 degrees latitude, about the same latitude as Philadelphia! The "draft" of an iceberg refers to how deep the base reaches into the water. It is true that the "tip of the iceberg" makes up only about 10 to 20 percent of it's mass. The large ice shelves off Antartica produce "tabular" icebergs with drafts of nearly 1,000 feet (these are flat-topped icebergs that are much longer than they are high.) Photos of the ocean floor in shallow areas show deep gouges caused by these icebergs. Smaller chunks ranging in size from a small car to a bungalow can be dangerous to ships because they're very low in the water and cannot be seen easily in choppy seas.

Friday

Icebergs that break off the glaciers of Newfoundland and into the North Atlantic rarely survive beyond two years. Melting from warmer ocean waters and erosion by waves generally cut it down to size. But it took thousands of years for the iceberg to form. The ice at the bottom of a Greenland glacier may have come from snow that fell 150,000 years ago. Scientists believe that the average age of ice within an iceberg is about 5,000 years. Becasue the ice is so pure and abundant, there has been talk about "harvesting" icebergs for water-poor areas. The plan involved having ships push large icebergs to New Zealand, where the ice would be melted and the resulting water stored. This freshwater then would be sold to the countries of the Middle East. The plan never made much progress. But entreprenters, on a smaller scale, have succeeded in harveting ice from bergs and marketing it.