Well, we know the answer, it’s climate change. But, what exactly, is causing the record breaking events in the past few years, such as the 2012 Watson River (Akuliarusiarsuup Kuua) event, where the bridge got washed away?
The mechanism (and here is where I apologize to arctic climatologists for the comparison) is much like what we see on glaciers. Many of them are dirt/debris covered, and while darkening mechanisms may differ from Greenland, the net effect is the same: Dark surfaces heat up a lot more under sunlight than bright white, freshly snow covered surfaces. Halfway between is melting snow, which changes its crystal structure, but also is much darker than fresh snow.
So, to get record breaking melt events, here is the recipe for disaster for Greenland:
- Less snow during winter than decades ago
- leading to a thinner layer of snow that, if
- there is a few unusually warm days above 0 deg C early in the year, starts to melt, which
- causes it to darken, thus accelerating the melt, until
- the dark grey Greenland ice has lost its protective cover, which causes melt rates to ramp up significantly
You can get a feel for this using the app below, which takes PromICE data, and displays a relevant subset of it (altitudes up to 1500 m), binned in hex form (using Uber’s h3 library) showing areas of fresh, white snow, darker, wet snow, and dark bare ice regions. You can tell that, around the time when the Watson River bridge got washed away, Greenland was, actually, Greyland (play with the dates, set it to June 1, June 30, then May and September).
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Title image https://en.wikipedia.org/wiki/File:Glacier_mouth.jpg