Old soil carbon (C) respired to the atmosphere as a result of permafrost thaw has the potential to become a large positive feedback to climate change. As permafrost thaws, quantifying old soil contributions to ecosystem respiration (Reco) and understanding how these contributions change with warming is necessary to estimate the size of this positive feedback. We used naturally occurring C isotopes (δ13C and Δ14C) to partition Reco into plant, young soil and old soil sources in a subarctic air and soil warming experiment over three years.

The Arctic is warming roughly twice as fast as the global average. If greenhouse gas emissions continue to increase at current rates, this warming will lead to the widespread thawing of permafrost and the release of hundreds of billions of tonnes of CO2 and billions of tonnes of CH4 into the atmosphere. So far there have been no estimates of the possible extra economic impacts from permafrost emissions of CO2 and CH4.

The indigenous people of Greenland, the Inuit, have lived for a long time in the extreme conditions of the Arctic, including low annual temperatures, and with a specialized diet rich in protein and fatty acids, particularly omega-3 polyunsaturated fatty acids (PUFAs). A scan of Inuit genomes for signatures of adaptation revealed signals at several loci, with the strongest signal located in a cluster of fatty acid desaturases that determine PUFA levels.

Large amounts of methane (CH4) are known to be emitted from permafrost environments during the autumn freeze-in, but the specific soil conditions leading up to these bursts are unclear. Therefore, we used an ultrawide band ground-penetrating radar in Northeast Greenland in autumn 2009 to estimate the volumetric composition inside the soil through dielectric characterization from 200 to 3200 MHz. Our results suggest a compression of the gas reservoir during the phase transition of soil water, which is accompanied by a peak in surface CH4 emissions.

Albedo modification (AM) is sometimes characterized as a potential means of avoiding climate threshold responses, including large-scale ice sheet mass loss. Previous work has investigated the effects of AM on total sea-level rise over the present century, as well as AM's ability to reduce long-term (Gt103 yr) contributions to sea-level rise from the Greenland Ice Sheet (GIS). These studies have broken new ground, but neglect important feedbacks in the GIS system, or are silent on AM's effectiveness over the short time scales that may be most relevant for decision-making (<103 yr).

Volcanic eruptions contribute to climate variability, but quantifying these contributions has been limited by inconsistencies in the timing of atmospheric volcanic aerosol loading determined from ice cores and subsequent cooling from climate proxies such as tree rings. Here we resolve these inconsistencies and show that large eruptions in the tropics and high latitudes were primary drivers of interannual-to-decadal temperature variability in the Northern Hemisphere during the past 2,500 years.

The air–sea transfer of heat and fresh water plays a critical role in the global climate system. This is particularly true for the Greenland and Iceland seas, where these fluxes drive ocean convection that contributes to Denmark Strait overflow water, the densest component of the lower limb of the Atlantic Meridional Overturning Circulation.