Nitrous oxide (N2O) is a stratospheric ozone-depleting agent and a potent greenhouse gas with a global warming potential 300 times that of carbon dioxide. Many human activities give rise to nitrous oxide – agriculture, fossil fuels, pollution – and, not surprisingly, most research on this potent gas has focused on these human driven sources. Recently, however, as part of our NERC funded work in the arctic and through our UK based, climate-warming experiments, we have shown that, in the absence of human activity, pristine ecosystems actually consume nitrous oxide i.e. they provide a sink for this potent gas. Moreover, temperature appears to regulate this behaviour and the sink is strongest in cold ecosystems. This is entirely novel, blue-skies research with only one piece of tangentially related literature. Hence, the aim of this PhD – using isotopic and molecular tools – is to pioneer the characterisation of the nature of this novel sink for nitrous oxide, which is likely to be some form of biological fixation and to see how it is affected by warming. The project will be both field and laboratory based, working in Iceland and the UK and would suit applicants with a geochemical, microbiological or general ecological interest.