Rapid expansion of Greenland's low-permeability ice slabs.

In recent decades, meltwater runoff has accelerated to become the dominant mechanism for mass loss in the Greenland ice sheet. In Greenland's high-elevation interior, porous snow and firn accumulate; these can absorb surface meltwater and inhibit runoff, but this buffering effect is limited if enough water refreezes near the surface to restrict percolation. However, the influence of refreezing on runoff from Greenland remains largely unquantified.

Considering thermal-viscous collapse of the Greenland ice sheet.

We explore potential changes in Greenland ice sheet form and flow associated with increasing ice temperatures and relaxing effective ice viscosities. We define "thermal-viscous collapse" as a transition from the polythermal ice sheet temperature distribution characteristic of the Holocene to temperate ice at the pressure melting point and associated lower viscosities. The conceptual model of thermal-viscous collapse we present is dependent on: (1) sufficient energy available in future meltwater runoff, (2) routing of meltwater to the bed of the ice sheet interior, and (3) efficient energy transfer from meltwater to the ice.

End of the Little Ice Age in the Alps forced by industrial black carbon.

Glaciers in the European Alps began to retreat abruptly from their mid-19th century maximum, marking what appeared to be the end of the Little Ice Age. Alpine temperature and precipitation records suggest that glaciers should instead have continued to grow until circa 1910. Radiative forcing by increasing deposition of industrial black carbon to snow may represent the driver of the abrupt glacier retreats in the Alps that began in the mid-19th century.