In 1968 John Mercer, a glaciologist at Ohio State University, pointed out a problem with the West Antarctic Ice Sheet the WAIS, this is a smaller, but still enormous, mass of ice, separated by a mountain range from the bulk of the continent. Adventures who had traversed the ice during the International Geophysical Year 1957-58 had shown that much of the base of this mass was below sea level. Mercer argued that it was held back from flowing into the ocean, in a delicate balance, only by the shelves of ice floating at its rim. These shelves might disintegrate under a slight warming. The much larger mass of ice corked up by the shelves would then be released to slide into the ocean and disintegrate into icebergs. Just so, Mercer suggested, a collapse of ice sheets into the Arctic Ocean might have caused the more local, but remarkably sudden, cooling of the North Atlantic around 11,000 years ago that other scientists had identified. A West Antarctic Ice Sheet collapse could be very rapid, Mercer said. The sea level would not rise as far as it would rise if all of Antarctica surged, but it would be bad enough — up to five meters, he estimated (16 feet; calculations decades later pinned down the number at
around 11 feet). Much of the world's population lives near the shore. Such a rise would displace more than a billion people and force the abandonment of many great cities. Mercer thought it could happen within the next 40 years
Mercer published his worries in an obscure conference report, and although he wrote forcefully, he did not push his views on colleagues in the personal encounters that are crucial in a small community of specialists. The few specialists who heard of his ideas were not impressed. The problem, one of them complained, "could be argued indefinitely if it is not quantified.”
Glaciologists had been working for decades on ways to calculate numbers for the flow of ice masses. In the 1970s they made rapid progress in formulating abstract mathematical models and putting the powerful new computers to work. The calculations, with many approximations, suggested that the West Antarctic Ice Sheet was indeed unstable. Apparently the floating ice shelf that held it back could break up with surprising ease, and the whole mass might begin sliding forward. One scientist who made a landmark calculation, Johannes Weertman, concluded that it was "entirely possible" that the West Antarctic Ice Sheet was already now starting its surge
I was a little surprised when I found this report, as I had never, over the years heard of such a thing.
It appears Mercer’s prediction of forty years may be off a decade or two, but at this point, seems unstoppable.
