Article content continued

How much would be released depends on how much the permafrost thaws – which in turn depends on the volume of greenhouse-gas emissions and subsequent warming of the planet. But permafrost thaw has begun in some places and scientists project that it will continue over the course of the century. The study says that with current emissions levels through 2100, permafrost could shrink by between 30 and 99 percent.

The question then becomes where this mercury will go, and what it will do – and the scientists say they aren’t sure of that. It could flush out through rivers into the Arctic Ocean. Or it could enter the atmosphere. Or both. That remains to be determined.

We figure that this represents the buildup of mercury during and since the last Ice Age

The problem is that mercury, although naturally occurring, is damaging to humans and wildlife, especially in certain forms. We’re already causing buried mercury to enter the atmosphere by burning coal, which lofts the element into the atmosphere, where it travels long distances. When it rains out into the ocean or lakes, it enters the food chain, first accumulating in the bodies of microorganisms and then growing increasingly concentrated in predators that feed off smaller organisms – for instance, larger fish.

When humans consume mercury-laden fish in quantities too large, it can be dangerous – especially for pregnant women.

In the Arctic, mercury can also accumulate in the bodies of major mammal predators, such as polar bears or narwhal, a phenomenon that has been documented. If the Arctic mercury burden further increases, it could be yet another way that climate change takes a toll on the native communities living there.