Ice could cover Arctic coastal regions for only half the year by the 2070s, if human-induced climate change continues.

Most of these areas are now covered in ice for more than half the year, and even all year in some places. Using data on daily sea-ice concentrations, Katherine Barnhart at the University of Colorado Boulder and her colleagues mapped changes in the Arctic's open-water season since pre-industrial times, and used models to project future changes. They found that throughout the Arctic, the season began to lengthen in the 1990s, with ice break-up starting earlier and freeze-up setting in later. In business-as-usual climate-change scenarios, the models indicate that the duration of open-water seasons for much of the region will start to exceed pre-industrial bounds by the middle of this century.

The expansion of the open-water season will affect all aspects of the Arctic environment that depend on sea-ice coverage, such as polar-bear foraging and the livelihoods of indigenous people, the authors say.

Nature Clim. Change (2015)