During the exceptionally warm Arctic summer of 2019, Greenland lost 600 billion tons of ice, enough to raise global sea levels by 2.2 millimeters in two months (that’s a lot!). According to a study published in Nature in 2018, the melting is not just increasing, it’s accelerating. Melting in Greenland started to pick up shortly after the dawn of the Industrial Revolution in the mid-1800s, however it is only over the last 20 years that the melt rate has definitively increased beyond natural variability. _
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Greenland’s runoff hit a 350-year high in 2012, when the ice sheet released about 600 gigatonnes of water – enough to fill 240 million Olympic swimming pools. Globally, average sea levels have increased by around 3.5 millimetres per year since 2005. Greenland is a significant contributor to that rise, accounting for nearly 22% of the total, according to the World Climate Research Programme. So why is it melting so fast? _
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There are a few contributing factors – Greenland typically gains some ice in the winter and loses some in the summer, however as the planet has warmed, the rate of ice loss has outpaced the rate of ice gain. The ice sheet itself is also changing – the firm layer in the ice sheet is heating up and becoming denser. This means that water that would ordinarily trickle down through the snow and refreeze as it contacts ice runs off the sheet instead._
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The ice is also getting darker, as soot carries through the air and microorganisms like algae coat the ice. This results in the ice absorbing more sunlight, which heats it up and increases melting, which in turn allows the microorganisms to spread further._
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All of these factors create a feedback loop where changes in the climate and in the ice cause an accelerated rate of melting. This in turn results in higher sea levels, putting millions more people at risk around the world. If this accelerated rate of ice loss continues, it is possible that new tipping points may be breached sooner than we previously thought. _
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Source: PBS, Vox, Nature, WCRP, NOAA
