Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain
the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in
Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles
and JavaScript.
Nearly one-quarter of the land in the Northern Hemisphere is underlain by permafrost. As this frozen soil melts, it releases large amounts of carbon dioxide and methane, and also alters surface hydrology. In this focus, we present a collection of research and comment pieces that look at the current effects of melting permafrost and assess how this vast carbon store could influence climate in the future.
Methane emissions from natural gas reservoirs have long been largely overlooked. The discovery of abundant geological gas seeps in areas of cryosphere degradation highlights the relevance of these emissions to the greenhouse gas budget.
Large quantities of methane lie trapped beneath the floor of the Arctic Ocean. Measurements in the southern Laptev Sea around the Lena River delta suggest that bubbles and storms facilitate the flux of some of this submarine methane to the atmosphere.
Lakes are sources of the greenhouse gas methane. A synthesis of measurements of methane emissions reveals that lakes and ponds above 50 °N emit 16.5 Tg methane annually, and emissions may increase by 20 to 50% with longer ice-free seasons.
The impact of thawing permafrost on the nitrogen cycle is uncertain. Laboratory experiments using permafrost cores from northeast Greenland reveal that rewetting of thawed permafrost increases nitrous oxide production over 20-fold.
Uptake of atmospheric CO2 contributes to ocean acidification. Measurements of seawater chemistry reveal that the extreme acidity of the East Siberian Arctic Shelf is driven by terrestrial organic matter and freshwater inputs.
Permafrost soils contain almost twice as much carbon as the current atmospheric carbon pool. Climate model simulations suggest that the feedback generated by future permafrost carbon release could lead to a further warming of 0.13–1.69 °C by 2300.
High Arctic soils can act as sources or sinks of methane. Scaled-up field measurements suggest that northeast Greenland’s ice-free soils currently act as a net sink for methane, and may take up more methane with rising temperatures.
Vast quantities of carbon are stored in shallow Arctic reservoirs, such as subsea and terrestrial permafrost. Observations in the Laptev Sea suggest that bubbles deliver significant quantities of the methane stored in subsea permafrost to the overlying water column.
The polygonal patterns in permafrost regions are caused by the formation of ice wedges. Observations of polygon evolution reveal that rapid ice-wedge melting has occurred across the Arctic since 1950, altering tundra hydrology.