A Land of Darker Green

A shadow falls across this land,
unseen shades that consume the light
and expose elder memories
to the brilliance of their imperfections.
Mischievous systems loiter with intent –
clockwise streams that buckle overhead,
scaring snowstorms and coercing clouds
with the warmth of their approach.

Rounded,
blunt,
shorn.

You drift towards
this pristine sheet
of floating uncertainty –
every flake
a blackened nail
in the umbrage
of its passing.

The Greenland Ice Sheet; East Greenland – Ammassalik District (Image Credit: Kitty Terwolbeck).

This poem is inspired by recent research, which has found that Greenland is becoming darker and warmer due to a weather pattern that is pushing fresh snowfall away from its ice sheet.

The Greenland Ice Sheet is the second largest mass of ice on Earth, holding enough water to raise global sea levels by 7.2 metres. It has warmed by approximately 2.7 degrees Celsius since 1982 and is currently experiencing what is thought to be the greatest melt and runoff rates in in the last 7,000 years. The albedo of the Greenland Ice Sheet (i.e. the fraction of light that is reflected by a body or surface) has decreased over recent decades, meaning that more of the sunlight is being absorbed instead of reflected, thereby contributing to enhanced surface melt and mass loss. However, it has been unclear as to whether this darkening is due to increased impurities in the snow, larger snow grain sizes, or both.

In this new study, researchers gathered data during a 2,700-mile snowmobile trek across a region of the Greenland Ice Sheet known as the western percolation zone. In analysing samples of this snow, they found only about 1 part per billion of impurities in the snow, thereby demonstrating that rather than soot, dust, or microorganisms, the likely cause of the darkening is actually the changing shape and frequency of snowflakes. These changes are forced by persistent high-pressure systems, which hover over the region for up to weeks at a time, pushing snowstorms to the north, holding warmer air over Western Greenland, and reducing sunlight-blocking cloud cover. As well as reducing the amount of snowfall, these high-pressure systems also alter the way in which the snow is actually formed. As snowflakes melt or evaporate, they become more rounded and less reflective than newer, crystal-shaped snow, causing the snow surface to become even darker and resulting in an amplitude of this effect. It is essential that the degree of this darkening is carefully monitored, as even a 1% change in reflectivity across the Greenland Ice Sheet could cause an additional 25 billion tons of ice to be lost over a three-year period, which would have severe repercussions for global sea levels.

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