February 9, 2013 — On September 16th 2012, at the height of the summer melt, the Arctic Ocean’s ice sheet had shrunk to an area of 3.41m square kilometres (1.32m square miles), half what it was in 1979. And its volume had shrunk faster still, to a quarter of what it was in 1979, for the sheet is getting thinner as well as smaller. One culprit is global warming, which is fiercer at the poles than elsewhere. The world’s average temperature in 2012 was nearly 0.5°C above the average for 1951-80. In the Arctic, it was up almost 2°C.
This sudden warming is like the peeling back of a lid to reveal a new ocean underneath. That prospect is spreading alarm (among greens) and excitement (at the natural resources and other economic opportunities that could be unveiled). Though most of the excitement has been about oil and gas, and the opening of sea routes between the Atlantic and the Pacific, some people hope for a fishing bonanza, too, as warmth and light bring ecological renewal to what is now an icy desert. But they may be disappointed.
At the moment, the waters around the Arctic account for a fifth of the world’s catch. There are few fish, however, under the ice itself. A fishing bonanza would require big ecological change. Arctic Frontiers, a conference organised at the University of Tromso in January, looked at how warming will change the ecology, to estimate whether it will bring one about. The consensus was that it won’t—not because the Arctic will change too little, but because it will change too much.
Change and decay
At first sight, this is counterintuitive. As the ice melts, more light can reach the water, and that means more photosynthesis by marine algae. In the past, algae began to grow under the ice sheet in May and continued to do so until late September. Now, such growth starts in mid-March and continues until October. These ice algae, attached to the sheet itself, account for half the mass of living things in Arctic waters. Much of the rest is unattached algae, known as phytoplankton, and tiny animals, known as zooplankton. Both sorts of plankton support, directly or indirectly, the fish and mammals that live in the Arctic Ocean. And the plankton, too, are flourishing thanks to global warming. The Arctic phytoplankton bloom, which used to run from June to September, now runs from April to September.
The upshot is more plankton, farther north. That attracts more fish. In 2000 Atlantic cod were caught throughout the Barents Sea. By 2012 their distribution was skewed towards the northern part of that sea. Stocks of capelin (a small fish eaten by cod) used to be concentrated south of Svalbard, at latitude 75°N. In 2012 this had moved to 78°N. Some found their way as far up as 80°N.
Read the full story at The Economist