Global temperatures are rising and as a result icecaps are melting. But as a study in Nature Climate Change shows icecaps don’t just discharge water when they melt. They also release a gift from generations past in the form of persistent organic pollutants (POPs).

Normally one would consider it nice to receive a gift from their grandparents, but not in the case of POPs. These man-made molecules are highly resistant to environmental degradation, sometimes taking decades to break down in nature. They were extensively used as industrial chemicals and pesticides until the Stockholm Convention banned their production and trade in 2001.

Due to their persistence in the environment, POPs travel long distances through the atmosphere, accruing in regions where low temperatures induce their deposition, like in the Arctic. But higher temperatures will just as easily remobilise them, rereleasing them into the atmosphere or ocean. In more populated areas the chemicals pose serious health risks while they accumulate in wildlife and humans, with increasing concentrations for each step up the food chain.

Between 1993 and 2009 scientists looked at atmospheric concentrations of three POPs: DDT, HCH and cis-chlordane at Norway’s Svalbard Islands and in the Canadian Arctic. A down-ward trend was clearly noticeable since their outlaw in 2001. But when the effect of global warming on POP concentrations was taken into account a completely different and far more unsettling picture arose. A slight rise in secondary emissions was found as a result of the release of POPs previously sealed in ice and snow but now steadily released because of rising temperatures.

Due to Arctic warming, the past two decades have shown a revolatilisation of a broad array of POPS into the atmosphere. As a result the global efforts to reduce environmental and human exposure to these compounds might have been seriously damaged.

But the release of POPs from the arctic could just be a forerunner. Since the Arctic has shown to be much more sensitive to warming than other parts of the planet, other stores of POPs, such as soil and the deep sea, might follow with a continued rise in temperature.

© Jorn van Dooren | www.bitsofscience.org