greenland

When summer temperatures rise in Greenland and the melt season begins, water pools on the surface, and sometimes disappears down holes in the ice. That water may eventually reach bedrock, creating a slipperier, faster slide for glaciers. But where does it go once it gets there, and what happens to it in the winter? A new study helps answer these questions.

Scientists have found evidence in a chunk of bedrock drilled from nearly two miles below the summit of the Greenland Ice Sheet that the ice nearly disappeared for an extended time in the last million years or so. The finding casts doubt on assumptions that Greenland has been relatively stable during the recent geological past, and implies that global warming could tip it into decline more precipitously than previously thought. Such a decline could cause rapid sea-level rise. The findings appear this week in the leading journal Nature.

Greenland's snowy surface has been getting darker over the past two decades, absorbing more heat from the sun and increasing snow melt, a new study of satellite data shows. That trend is likely to continue, with the surface's reflectivity, or albedo, decreasing by as much as 10 percent by the end of the century, the study says.

Seismologists at Columbia University and Harvard University have found a new indicator that the Earth is warming: "glacial earthquakes" caused when the rivers of ice lurch unexpectedly and produce temblors as strong as magnitude 5.1 on the moment-magnitude scale, which is similar to the Richter scale. Glacial earthquakes in Greenland, the researchers found, are most common in July and August, and have more than doubled in number since 2002.