Castles of the sea

By GUS FANNING

St. JOHN'S, NF (May 12, 2004) -- Living as we do, on the axis of the Labrador Current, Newfoundlanders are no strangers to icebergs. Those majestic pillars that grace our shores between the months of March and August are awe-inspiring and often terrifying at the same time. But what do we really know about them?


Iceburg in St.John's Harbour

Roughly 90 per cent of Newfoundland's icebergs originate from glacial ice laid down by millennia of snow accumulation in Greenland's narrow valleys. The remainder come from Canadian sources such as the Ward Hunt ice shelf.

These vast rivers of ice edge slowly towards the sea under their own weight at a rate of several metres a day. Thus, icebergs seen today may have been formed 3,000 years ago.

The action of warm ocean waters, waves and tides break off bergs, either as spectacular cascades of ice resembling towering pillars known as "pinnacle bergs," or the flat "tabular" ice fields.

While 10,000-20,000 icebergs are calved each year from over 20 major glaciers along Greenland's coast, usually only a small percentage (perhaps less than 10 per cent) ever reach our waters, as many melt prior to their visit of our shores.

Tip of the iceberg

Owing to the fact that ice density is roughly 10 per cent less than seawater, only about 10 per cent of the iceberg is visible above the sea surface (hence the term "tip of the iceberg"). Extending to such great depths below the ocean surface, iceberg motion is controlled primarily by subsurface currents rather than wind drift.

And what's below the surface can potentially cause the most trouble. Deep draft icebergs (such as pinnacle bergs) scour the ocean floor, damaging deployed instrumentation and infrastructure.

Of potentially more hazard are the tabular icebergs. While they extend only 10 metres above the sea surface, these bergs can extend to vast areas and reach masses exceeding 100,000 tonnes.

Further complicating shipping are the "bergy bits" and "growlers." Less than four metres high on the surface, these icebergs masquerade as pack ice and are virtually undetectable on a ship's radar.

How many are there?

Following the sinking of the Titanic in April 1912, the International Ice Patrol was formed and the first comprehensive study and records of icebergs were made (although some records do extend back to the 1880s).

The iceberg severity index dating from that time shows that the number of icebergs is highly variable. For instance, from the late 1940s to the early 1970s, very few icebergs crossed the 48th parallel (roughly the latitude of the Grand Banks). More recently, the index has shown considerable variation with as few as 22 icebergs in 1999, compared to 1,011 in 1997 and 1,380 in 1998.

"This year is shaping up to be a very light iceberg season, with less than 100 bergs," says Pat Barron Jr., operations manager of Provincial Airlines' Environmental Services Division.

Predicting icebergs

The idea of El Nino as a feature of our weather has become entrenched in popular culture, primarily because of its devastating social and economic impact throughout the Pacific and as far downstream as Quebec (recall the severe ice storms in the 1990s).

Less well known, but of potentially more importance locally, is a phenomenon known as the North Atlantic Oscillation (NAO).

The NAO is best described as a seesaw in sea-level pressure with centres of action near Iceland and the Azores. When this see-saw is in its "high phase," ice export (in the form of icebergs and pack ice) is significantly enhanced from the Greenland/Iceland seas through Fram Strait and ultimately into the Labrador Current system.

The NAO usually oscillates every two to four years. However, from the early 1970s, the NAO appears to have become "locked" into a predominantly high phase mode, a phenomenon unprecedented since the period 1900-1930. During the years 1973-75, between 1,000 and 1,300 icebergs were recorded in the ice severity index; similarly, from 1983-85 and 1990-95, between 1,200-2,000 and 1,500-2,000 were recorded respectively.

With this apparent phase-locking of the NAO, and concerns over a disintegrating glacial mass due to global warming, renewed interest has arisen in iceberg tracking and prediction.

Locally, Provincial Airlines Limited (PAL) Environmental Services provides aerial reconnaissance for offshore oil and gas exploration interests and the Canadian Ice Centre.

Utilizing anti-submarine warfare radar, thermal imaging and camera technology, PAL combines multiple image tracks of icebergs with computer software to monitor ice drift and project future tra- jectories in an effort to reliably assess potential risks to offshore facilities.

How to move an iceberg

Since oil platforms are either incapable of movement, or rather costly to move, the only option remaining is to move the iceberg. While this may sound simple, it's anything but.

A number of mechanisms exist (or are in development) to alter the path of icebergs to remove their threat to oil-drilling platforms. Beginning in the early 1970s, technology was developed to "lasso" icebergs. Once roped, the bergs are gently nudged to slightly alter their drift so that after traversing the vast distance to drilling operations, the bergs no longer pose a threat.

According to PAL, over the past 20 years, 85 per cent of icebergs towed have been successfully altered from their path, posing no threat to offshore interests. Alternative methods involve water cannon. Explosives are being considered to reduce the draft of pinnacle icebergs.

Iceberg industry

The story doesn't end there, though. In 1978, Arab interests opened talks on using the lasso technology to capture the large tabular icebergs, reshape them for ready towing and transport them through the Strait of Gibraltar to the Red Sea. Although the iceberg would lose considerable mass en route, the need for fresh water is so great that enough of the ice would remain to make the project profitable.

In a similar fashion, icebergs are routinely "harvested" off Alaska for designer ice cubes for sale in Japan, and locally, to make our own brand of Iceberg Vodka.

*Gus Fanning is an oceanographer in St. John's.



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