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Saturday, September 18, 2021

5 Trillion Tons of Ice Lost from Greenland

Greenland ice sheet mass balance from Mankoff et al 2021.

Equivalent sea level rise is on the scale to the right; cumulative mass loss is on the scale to the left.


8 comments:

  1. my back of envelope makes that between 15 and 16 cubic kilometers. staggering.

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  2. That must not be right. Wolfram Alpha suggests that 5 trillion tons of ice = 4948 km^3 = ~124 Km^3/year (over 40 years).
    - https://www.wolframalpha.com/input/?i=5+Trillion+Tons+of+Ice+in+cubic+kilometers

    Wikipedia says "In 2006, estimated monthly changes in the mass of Greenland's ice sheet suggest that it is melting at a rate of about 239 cubic kilometers (57 cu mi) per year. A more recent study, based on reprocessed and improved data between 2003 and 2008, reports an average trend of 195 cubic kilometers (47 cu mi) per year.[13]"

    Even at this rate though, Greenland ice would melt in 2,850,000/195= ~14,500 years or 2,850,000/195= ~12,000 years.

    Of course there are impacts along the way, and the rate is clearly accelerating. Just want to add the denominator for perspective.

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  3. To put these figures into perspective, 360 cubic kilometres of Greenland ice melt produces 1mm of sea level rise.

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  4. That 5 trillion tone of ice is 5000 cubic kilometres and raised sea level by

    5000/360= 14mm

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  5. So it's contributing something north of 1mm to SLR every other year based on the studies referenced in the Wikipedia article.

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  6. L: Yes. But until the last few years, Greenland ice loss was accelerating. Not sure why the acceleration has slowed down but I doubt it's likely to stick.

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  7. IIRC about 40% of sea level rise is due to thermal expansion, 25% each from Greenland and Antarctica The remaining 10% includes mountain glaciers, water from aquifers etc.

    At the current 4mm/year thermal expansion contributes 1.6mm, Greenland and Antarctica 1mm each, and the rest 0.4mm.

    By volume that would be an increase of 1440 cubic kilometres/year. 576 from thermal expansion, 360 each from Greenland and Antarctica, 144 from the rest.

    Each cubic kilometres weighs 1 billion tonnes. The 5 trillion tonnes mentioned above is 5000 cubic kilometres.

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  8. "until the last few years, Greenland ice loss was accelerating. Not sure why the acceleration has slowed down but I doubt it's likely to stick."

    It's been a quiet few years in the Arctic, with less melting than the "new normal". Less heat melting ice in the Arctic also probably means less heat melting in Greenland.

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