Proc. Natl Acad. Sci. USA 113, 46–51 (2016)

Warming in the Arctic is decreasing sea ice, which could have implications for the hydrological cycle of the region. Higher temperatures and an exposed ocean surface will increase evaporation, with the expectation that precipitation will correspondingly increase. Although this trend is shown by modelling studies, there has been a lack of observational evidence.

To address this issue, Ben Kopec of Dartmouth College, Hanover, USA and colleagues analysed the hydrogen and oxygen isotopic composition of precipitation at six sites for the period 1990–2012. This isotopic signature reveals moisture source changes (with contributions from both local and subtropical locations), which is then related to sea ice extent. The sites are grouped into two regions, the Canadian Arctic and Greenland Sea, with all locations in the same region having the same local moisture site — Baffin Basin and Greenland Sea, respectively.

The authors show that for every 100,000 km2 sea ice loss, the percentage of local moisture increases by ∼18% and ∼11% for the Canadian Arctic and Greenland Sea sites, respectively. This increased proportion of local moisture indicates there could be an overall increase in precipitation and impact of the region energy balance, which would have implications for climate projections.