Polar Ice: Problems with a Potential Natural Resource

Icebergs taller than a 50-story building and larger than the country of Belgium have been documented (it should be stressed here that we are speaking of fresh water ice derived from continental glaciers--not ice floes which are flat expanses of frozen sea water sometimes the size of small continents). It is no wonder that some countries have been semi-seriously considering the idea of towing one of these behemoths to the Middle East to provide a fresh water source that would last for many years.

Even if such a plan were feasible (which, at present, it is not), there would remain a problem which even the most sophisticated engineering might not be able to overcome.

One might regard such a massive piece of real estate as being almost indestructible (except through melting, of course), but the fact is that they are remarkably fragile, and often unexpectedly shatter into many smaller fragments. The tendency for them to do this has long baffled investigators.

Now, Vernon Squire, an oceanographer with the Scott Polar Research Institute in Cambridge, England, may have discovered the reason.

Squire and his colleagues mounted "strainmeters" on a number of icebergs in the Antarctic and monitored the small distortions resulting from the "surf" around the bergs' margins. It was found that each iceberg has a unique resonant frequency of vibration, depending on its size and shape. Although it would seem that ordinary ocean waves should have little effect on such a massive body, if the wave frequency matches that of the iceberg (or of one of its harmonics), the expansion and contraction induced could build to the point where the iceberg shatters. A good analogy, says Squire, would be that of a singer's voice shattering a wine glass.

The process is then repeated with the smaller pieces, each of which has a higher resonant frequency, until the bulk has been reduced to the point that only waves of unattainable frequency could damage it further.

If one were to seriously entertain the idea of transporting a large glacier from the polar regions to the tropics, a possible solution to prevent its breakup due to wave action is the obvious one of building a mobile breakwater around it. This has not only been suggested, but so has the prospect of enclosing the thing entirely in some sort of insulating material, thus protecting it from warm water and making it, in effect, a gigantic thermos jug.

If these ideas sound fanciful and only barely on this side of the lunatic fringe, consider that, during World War II, the Allies gave serious consideration to the construction of huge aircraft carriers made from ice floes, hollowed out in the central part to provide for living quarters and maintenance shops, and using the flat top of the floe as a landing surface.

The necessity, of course, never arose, but during the dismal early stages of the war, it seemed a distinct possibility. It is unlikely that at that time the problems of instability under resonant wave action had even been considered.