Those mighty little things are methane bubbles. This greenhouse gas is a byproduct of anaerobic decomposition. Mapping the bubbles trapped in the ice (which can conveniently be done up here in the arctic) tell us where the seeps in sediments are. The size of the bubbles and the clusters they form tell us something about how much methane they hold.
Methane is emitted from soils, wetlands, lakes all over the world. Subarctic and Arctic lakes have the particularity to be strong emitters of methane, due to thawing permafrost (source of organic matter). They also have been little studied.