Tidewater Glaciers Melting Underwater at Astonishing Rates Than Previously Predicted

A new study on a tidewater glacier reveals that its underwater ice melting is happening unpredictably rapidly.

Tidewater Glaciers Melting Underwater at Astonishing Rates Than Previously Predicted
LeConte tidewater glacier in Alaska jjgervasi/iStock

Global warming, as its name suggests, has been creating warmer climes, and that includes water. As water has been heating up globally so have icebergs, all of which are melting at fast rates. 

But, it hadn't been predicted to be quite so fast. 

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A recent study on tidewater glaciers, and the LeConte tidewater glacier in Southeast Alaska, in the U.S., in particular, has demonstrated that predictions of their underwater ice melting rates is in fact wrong. 

The ice is melting much more quickly than anticipated. 

What is a tidewater glacier?

Tidewater glaciers are 'valley glaciers' which flow directly from the land into the ocean or the sea.

These types of glaciers create or calve, chunks of icebergs directly into the water.

Tidewater Glaciers Melting Underwater at Astonishing Rates Than Previously Predicted
LeConte glacier calving. Source: Scott Ableman/Flickr

Tidewater glaciers move slowly into the ocean, and the calving of icebergs happens when the end of the glacier breaks because of the forward motion of the whole glacier.

They are known for being more dynamic than other glaciers, and subject to more changes due to their positioning and movement due to underwater melting. 

According to this new study, which used sonar surveys to carry out its research, the rate at which the ice is melting beneath the surface of the water is far faster than ever previously known or predicted. 

"Hotter waters"

It is already well-known that melting glaciers add to the rising global water levels - mostly due to global warming factors. 

What is less known, however, is that the actual understanding of tidewater glacier melt, as a direct reaction to accelerated warming in glacier environments, is based on very little evidence, indirect deductions, and an unconstrained theory behind underwater melting models. 

Tidewater Glaciers Melting Underwater at Astonishing Rates Than Previously Predicted
LeConte glacier bay. Source: J Brew/Flickr

The researchers, led by David Sutherland, noticed that direct measurements have never in fact been taken of underwater ice melting of tidewater glaciers. 

The team studied the LeConte tidewater glacier by carrying out repeat multibeam sonar surveys of the submerged section of the glacier.

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The survey was backed up against the ocean, ice and atmospheric measurements taken in 2016 and 2017, which altogether created a time-variable, three-dimensional record of the changes the glacier has undergone. 

These changes could be linked to melting and calving patterns of these glaciers.

What did Sutherland's team discover? 

Seasonally rising submarine melting all along the glacier face, and particularly, the fast rate at which it is happening.

The researchers urge that a pressing need to re-evaluate the existing models of tidewater glacier ice loss has to happen, quickly. 

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