When endless summer days reach the Arctic, the massive expanses of rarely-interrupted blinding white is cut by lakes and rivers of meltwater. The deep blue set against white is a unique, surreal beauty, creating an alien landscape that is smooth, crisp, and cool in its simplicity.
Researchers retrieving a parachuted canister of supplies. Image credit & read more: NASA/Earth Observatory
Although I've only rarely had opportunity to work on a glacier, I'm always captivated by their beauty. Hearing the rush of a stream carving through the ice below my feet is exhilarating, while the surface pools are so improbably blue that I can't stop staring at them. Glacial fieldwork is a mesmerizing contrast of blinding light and biting wind, of gritty snow and slick ice, of dedicated work and getting lost in wonder. While I'm sure this pair of researchers was mostly concerned about collecting the hardware needed by their icebreaker research vessel, I just know they were also taking a fair bit of time to be blown away by the mottled landscape around them.
Liquid water absorbs more heat than ice or snow, so when water pools on the ice, it can set up a feedback mechanism of increasing melting of surrounding ice, growing the melt pond. A single black pebble melting a tiny pool can grow and connect with hundreds of others, meltwater eroding banks of ice until enormous canyons cut through the glacier. While the most dramatic features take time to grow and change, even a few months can be the difference between a pond stretching over kilometers long, and a dry basin. Here's an example of a single melt feature in Greenland changing over the course of three months during a different mission in 2010:
A stream linking melt ponds in Greenland in June 2010. Image credit & read more: NASA/Earth Observatory
Melting ice has deepened the feature into one long melt pond with an icy island by July 2010. Image credit & read more: NASA/Earth Observatory
The pond is almost empty, possibly due to draining down a deep crack (moulin) in the basin. Rings mark the high-water line. Image credit & read more: NASA/Earth Observatory
The heat capacity of water isn't the only feedback mechanism at play with melt ponds. While it's simple to think of glaciers as massive expanses of crisp, clean white snow, in reality ice darkens to a dirty grey as it ages and incorporates dust, sediment, and imperfections.
As fresh snow melts, it exposes the darker ice. The colour difference can be substantial enough that dark ice can reflect 30% less energy than fresh, bright snow, absorbing the heat and producing further melting, exposing even more darker ice.
Melt ponds enhancing calving along an outlet glacier. Image credit & read more: NASA/Earth Observatory
The melting snow can even accelerate iceberg calving. As Robert Simmon explains for NASA's Earth Observatory Image of the Day:
As the ice sheet melts, water collects in large pools on the ice surface. Streams drain the pools, sometimes carrying water into other pools, but sometimes disappearing into crevasses or cracks in the ice. The crevasses take the water deep into the ice sheet, sometimes even to the underlying rock, where it lubricates the lowest layers of the ice. The lubricated ice flows more quickly toward the ocean, which in turn accelerates the rate at which icebergs break into the sea. The overall result is a greater loss in ice mass than would happen without the influence of melt water streams.
As new white snow melts into cool blue water, more old dark ice is exposes, promoting more melting. Image credit & read more: NASA/Earth Observatory
Meltwater carving up Petermann Ice Island A, fragment 2 in 2007. Image credit & read more: NASA/Earth Observatory
This summer, NASA mounted the Multiple Altimeter Beam Experimental Lidar (MABEL) on a reconnaissance plane to fly over the ice sheets, using a laser altimeter to measure any changes in elevation of the glaciers and other landforms below. This data will be used in designing algorithms for an upcoming Ice, Cloud, and land Elevation Satellite (ICESat-2) mission. It will also be paired with normal photographs to match up measurements with the distribution of melt ponds and other features of the summer terrain. Here's some of the features MABEL has seen so far this summer:
A lone melt pond resting on a glacier with a myriad of iceberg flecks. Image credit & read more: NASA/Earth Observatory
Melt ponds, streams, dirty ice, and snow. Image credit & read more: NASA/Earth Observatory
Cracked sea ice, melt ponds, and open water. Image credit & read more: NASA/Earth Observatory