Lessons from a melting Antarctic glacier

Context

  • In the Antarctic floats a massive glacier, roughly the size of Britain, whose melting has been a cause of alarm for scientists over the years. Now, a new study has pinned the cause of the melting to the presence of warm water at a vital point beneath the glacier.

What is the glacier and why is it important?

  • Called the Thwaites Glacier, it is 120 km wide at its broadest, fast-moving and melting fast over the years. Because of its size (1.9 lakh square km), it contains enough water to raise the world sea level by more than half a metre. Studies have found the amount of ice flowing out of it has nearly doubled over the past 30 years.
  • Today, Thwaites’s melting already contributes 4% to global sea level rise each year. It is estimated that it would collapse into the sea in 200-900 years. Thwaites is important for Antarctica as it slows the ice behind it from freely flowing into the ocean. Because of the risk it faces — and poses — Thwaites is often called the Doomsday Glacier.

What has the new study found?

  • A 2019 study had discovered a fast-growing cavity in the glacier sized roughly two-thirds the area of Manhattan. Then last week, researchers from New York University detected warm water at a vital point below the glacier. The NYU study was funded by the International Thwaites Glacier Collaboration, headed by the Natural Environment Research Council of the UK and the National Science Foundation of the US; the collaboration has been studying the glacier since 2018.
  • The New York University study reported water at just two degrees above freezing point at Thwaites’s “grounding zone” or “grounding line”.

Why is that significant?

  • The grounding line is the place below a glacier at which the ice transitions between resting fully on bedrock and floating on the ocean as an ice shelf. The location of the line is a pointer to the rate of retreat of a glacier.
  • When glaciers melt and lose weight, they float off the land where they used to be situated. When this happens, the grounding line retreats. That exposes more of a glacier’s underside to seawater, increasing the likelihood it will melt faster. This results in the glacier speeding up, stretching out, and thinning, causing the grounding line to retreat ever further.
  • “Warm waters in this part of the world, as remote as they may seem, should serve as a warning to all of us about the potential dire changes to the planet brought about by climate change,” David Holland of New York University said in a statement.

How was the warming water detected?

  • Scientists dug a 600-m-deep and 35-cm-wide access hole, and deployed an ocean-sensing device called Icefin to measure the waters moving below the glacier’s surface.
  • “The fact that such warm water was just now recorded by our team along a section of Thwaites grounding zone where we have known the glacier is melting suggests that it may be undergoing an unstoppable retreat that has huge implications for global sea-level rise,” Holland said.

Source:IE