2019 was the largest fire year since at least 1997 within the Arctic Circle, largely driven by Siberian fires. The arctic-boreal region stores about two atmospheres worth of soil carbon with 90 % currently locked in permafrost soils, or perennially frozen ground. Fire releases parts of this carbon stock, which may induce a vigorous climate warming feedback.<br/>FireIce will investigate feedbacks between climate warming and arctic-boreal fires by studying direct and longer-term carbon emissions from fires. FireIce will acquire highly needed observations of carbon emissions from Siberian forest and tundra fires. On top of the direct fire emissions, fires accelerate permafrost degradation, which leads to greenhouse gas emissions for several decades. Their sum may be substantially larger than the direct emissions, yet is largely unknown. In addition, FireIce will investigate the relative contribution of CH4 from smoldering fires to fire emissions. CH4 emissions represent a small, yet not well known, fraction of carbon emissions from fires, but CH4 is a more potent greenhouse gas than CO2.<br/>FireIce will investigate feedbacks between climate warming and arctic-boreal fires by studying controls on fire size and ignition. Fire growth can be limited because of fuel or fire weather limitations. The fire weather control is sensitive to warming, which may lead to larger future fires. Lightning ignition is the main source of burned area in arctic-boreal regions, and more lightning is expected in the future. By combining contemporary controls on fire size and ignition, and future predictions of climate and lightning, FireIce will assess the vulnerability of arctic-boreal permafrost and soil carbon to increases in fire. <br/>FireIce’s results will be relevant to evidence-based policy. FireIce’s innovations are conceptual, i.e. unstudied aspects of an emerging warming feedback loop, methodological, e.g. inclusion of novel spaceborne data, and geographical, i.e. a focus on Siberia.