Word: glaciered
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...that the trouble-plagued trans-Alaska pipeline is in full operation, Alaskan oil is flowing in great volume overland. But its journey to U.S. West Coast ports may soon be interrupted at sea -by icebergs in the tanker shipping lanes. The source of these floating hazards is the Columbia Glacier, a 425-sq.-mi. mass of ice that ends less than seven miles from the tanker lanes for Port Valdez...
...mile-long glacier originates high in a watershed east of Valdez, where it is fed by massive snowfalls. From there, it flows inexorably down toward Columbia Bay, where it terminates on a shoal across the fjord in shallow water. Like all glaciers that end at the sea, Columbia continually "calves" or drops chunks of ice off its face as it moves forward. This process can speed up dramatically when changing climatic conditions cause a glacier to begin thinning out. This decrease in thickness can destroy a glacier's delicate equilibrium and radically increase calving in a process called "drastic...
Columbia is the only calving glacier in western North America not to have experienced a drastic retreat in several thousand years. But ominous signs of instability have been reported by a U.S. Geological Survey team. Upstream from its face, the glacier has thinned by more than 30 ft. in one year, and since 1974, there have been periods of accelerated calving every summer. Says U.S.G.S. Glaciology Project Chief Mark Meier: "This suggests that there is not enough ice coming forward to keep up with the iceberg calving...
...result, the glacier's front end could shrink back off the shoal into the deeper water upstream. Its new face, extending to the bottom of the fjord, would then be three or more times the height of the old, and quite unstable. Calving could accelerate five to 50 times its current rate. As much as a cubic mile of ice might be dumped into the bay each year for the next 30 to 50 years, until the glacier retreats to a new and stable foothold...
...waterways now used by supertankers ferrying oil south to virtually halt traffic. Explains Coast Guard Captain Ronald Kollmeyer: "When you have literally thousands of icebergs in the shipping lanes, you can't drive an 800-to 900-ft. tanker through that sort of gauntlet." Last August, the glacier's calving increased enough to force closing of the Valdez lanes to night traffic for nearly a week...