Global Warming

Satellite spies methane bubbling up from Arctic permafrost

For the first time, scientists have used a satellite to estimate how much methane is seeping into the atmosphere from Arctic lakes. Preliminary data presented this week at a meeting of the American Geophysical Union in Washington DC help to explain long-standing discrepancies between estimates of methane emissions from atmospheric measurements and data collected at individual lakes.

As icy permafrost melts to form lakes, microbes break down organic matter in the thawing ground beneath the water and release methane, a potent greenhouse gas. Researchers have measured the amount of methane seeping out of hundreds of lakes, one by one, but estimating emissions across the Arctic remains a challenge. Understanding how much methane is being released by these lakes is crucial to predicting how much permafrost emissions could exacerbate future climate change.

The results suggest that previous research over-estimated how much methane was coming from many large lakes, partly because scientists have spent more time studying smaller lakes with relatively high emissions.

In a 2,000-square-kilometre area around the Barrow Peninsula in northern Alaska, for instance, the research team calculated that lakes release an average of 0.6 grams of methane per square metre of water surface each year — which equates to around 141 kilograms of methane per square kilometre. That is about 84% lower than some previous estimates based on measurements at individual lakes, but lines up well with estimates based on atmospheric measurements.