Thwaites Glacier: How Imminent is the Threat?

NASA/James Yungel

Thwaites Glacier, also called the Doomsday Glacier, is one of the largest glaciers in Antarctica and, at 62 miles across, it is also the widest glacier in the world. The whole thing is about the size of Florida and if it melted entirely, it would raise the global sea level by two feet.

What has scientists worried is that, as the picture below shows, the leading edge of the glacier sticks out about 30 miles from the shoreline and rests on an underwater seamount.

Thanks to global warming, the ocean around Antarctica has warmed, and currents are now eating away at the glacier from below. Cracks are appearing in the surface of the ice and it is expected that it (the cantilevered part) will collapse completely in the next five to ten years. This will only raise sea levels by a few millimeters, but it will expose the broad front of the land-based part of the glacier to warm water that will accelerate the rate of calving and the speed at which the glacier is flowing into the ocean.

If the entire glacier melted, it would raise sea levels by two feet, but it is so large that it’s collapse will draw other glaciers into the rapid flow towards the sea and this could raise sea levels by 25 feet.  Thwaites itself is a huge amount of ice, and so even with a more rapid flow into the sea, it could take up to a century to completely melt.  But scientists have had to regularly revise their estimates upwards as the planet warms, so no one really knows how fast it will melt.

During the previous decade, most scientists predicted that the oceans would rise by one to two feet by 2100.  Then, as the melting of ice in Antarctica and Greenland picked up speed, estimates went as high as 12 to 16 feet.  Now it seems that the general consensus has ratcheted back and is more like 4 to 8 feet – still enough to cause a lot of problems for coastal cities.  And, of course, time doesn’t stop in 2100.  The melting will continue at an accelerating pace and by 2200 sea levels may be 20 to 30 feet higher than today – or more.  It’s highly speculative, but it is consistent with the evidence.

So, it is hyperbole to say that Thwaites will dramatically raise sea levels by 2030, but sea level rise is happening and will keep happening faster and faster as we continue to burn fossil fuels and warm the planet even more.