Ice sheets matter for the global carbon cycle.

The cycling of carbon on Earth exerts a fundamental influence upon the greenhouse gas content of the atmosphere, and hence global climate over millennia. Until recently, ice sheets were viewed as inert components of this cycle and largely disregarded in global models. Research in the past decade has transformed this view, demonstrating the existence of uniquely adapted microbial communities, high rates of biogeochemical/physical weathering in ice sheets and storage and cycling of organic carbon (>10⁴ Pg C) and nutrients. Here we assess the active role of ice sheets in the global carbon cycle and potential ramifications of enhanced melt and ice discharge in a warming world. Ice sheets have long been overlooked as regulators of the global carbon cycle. In this Review, Wadham and colleagues show how the growth and retreat of ice sheets support the productivity of the oceans and variably store or release organic carbon–in effect, these frozen landscapes must be considered in future assessments of climate impacts on biogeochemical cycling. [ABSTRACT FROM AUTHOR]