Secret to Greenland’s ‘Vanishing’ Lakes

ENVIRONMENT

Teachers, scroll down for a quick list of key resources in our Teachers’ Toolkit, and don’t forget to take this week’s current events quiz!

Discussion Ideas

According to the Washington Post, Greenland’s ice sheet and supraglacial lakes melt unevenly. Where is the ice sheet more likely to decay? Take a look at the illustrations above for some older evidence, and the Washington Post article for some newer research.
- Old and new evidence both point to fast-moving coastal regions as more likely to decay than the thicker inland portion of the Greenland ice sheet. Here’s why:
  - Old evidence: The third item in the second illustration above says “thinner ice has a weaker grip on the land and can’t hold the accelerating glacier.”
  - New evidence: Meltwater from inland lakes runs along the surface of the ice sheet before pooling in coastal lakes and draining through moulins to the base of the ice sheet and out to sea.

According to the Washington Post, the melting of the Greenland ice sheet can contribute to sea level rise in two ways. What are they?
- Meltwater empties directly into the ocean.
- Meltwater eases the flow of tidewater glaciers, which calve off slowly-melting icebergs into the ocean.

Greenland’s “vanishing” lakes are largely a negative reflection of climate change, but the new research includes some good news as well. What is it?
- Geography to the rescue! According to the Washington Post, the research “suggests that meltwater lakes do not simply vanish of their own accord or under their own weight. Rather, they probably have to lie in a region where there’s another preexisting pathway for water to get under the ice in large amounts.”
  - MIT News puts it another way: “[I]t’s unlikely that inland lakes would drain, as there are fewer moulins near inland lakes, which prevents water from getting to the ground locally. Without these trigger channels, larger fractures would not form in the lake basin, and lakes would stay intact, simply refreezing in the winter or overflowing into a surface stream.”