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Mountain glaciers hold less ice than previously thought – it’s a concern for future water supplies but a drop in the bucket for sea level rise

Mountain glaciers hold less ice than previously thought – it’s a concern for future water supplies but a drop in the bucket for sea level rise

A herder moves sheep down a road next to a large water pipe with mountains in the background.

Nearly 25% of the world’s population depends on mountain glaciers as their primary water source. But figuring out just how much ice they hold – and how much water will be available as glaciers shrink in a warming world – has been notoriously difficult.

Scientists have mapped the speed and movement of more than 200,000 glaciers in a new study to find out why. They found that glacier volume estimates are widely used. May be reduced by around 20%In terms of how much the Greenland and Antarctic Ice Sheets could contribute to sea-level rise.

Mathieu MorlighemThe study was coauthored by, an expert in ice sheet modeling, and a coauthor. The new results hold a warning for regions that rely on glaciers’ seasonal meltwater, but barely register in the big picture of rising seas.

1) What does it mean for those who depend on mountain glaciers for water if they hold less ice than previously thought?

Globally, Nearly 2 billion peopleMany people rely on snowpack and mountain glaciers as their primary source of drinking water. Many people also depend on glacier water for hydropower generation and agriculture, especially in the dry season. The vast majority of glaciers worldwide are losing more mass each year due to climate change. These are slowly disappearing. That will. These populations are profoundly affected.

These communities must know how long their glaciers are expected to continue to provide water, and what to do if they disappear in order to be prepared.

We found significantly lower total ice volumes in most places than our previous estimates.

For example, in the tropical Andes (from Venezuela to northern Chile), we found that glaciers had 23% less ice then previously believed. This means that downstream communities have less time to adapt to climate changes than they might have anticipated.

A herder moves sheep down a road next to a large water pipe with mountains in the background.
A herder walks alongside a water pipe in Bolivia, near La Paz. The glacier that was once relied upon for water is almost gone.
Tim Clayton/Corbis via Getty Images

Even in the Alps, which have a lot of ice thickness measurements by scientists, we found that glaciers may have 8% more than previously thought.

The Himalayas are the exception. We found that these mountains could have 37% more glaciers than previously thought. This saves communities who depend on these glaciers some time, but it doesn’t change the fact that they are melting with global warming.

These estimates can be used by policymakers to improve their plans. Although we don’t make any predictions about the future, this study does give us some indications. a better descriptionHere are some images of the glaciers today and their water sources.

2) How does this affect future sea-level rise estimates?

First, it’s important to understand that melting glaciers are only one contributor to sea level rise as the climate warms. About one-third of today’s sea level rise is due to Thermal expansion of the ocean – as the ocean warms, water expands and takes up more space. The other two-thirds of the water comes from The shrinking of mountain glaciers and ice shelves.

We found that all the glaciers, including the large ice sheets in Greenland, Antarctica and Greenland, would melt completely if they were to melt completely. Sea level would rise by approximately 10 inchesInstead of 13 inches. Although it may seem like a huge difference, when you consider the ocean’s size, this is actually quite reasonable. A complete meltdown of the Antarctic Ice Sheet would be a contributing factor. 190 feetThe Greenland Ice Sheet and sea level would both contribute to this. 24 feet.

The 3 inches we are referring to in this study don’t question current projections of sea-level rise.

3) What is your study that showed how to determine the volume of ice in glaciers?

It is possible to be surprised at how little we know about the basic characteristics of mountain glaciers.

Satellites have changed our understanding of glaciers, since the 1970s. Glacier locations and surface area. But satellites cannot see “through” the ice. In fact, for 99% of the world’s glaciers, there is no direct measurement of ice thickness. Scientists have spent more time mapping them. Greenland and Antarctica Ice SheetsWe have more detailed volume measurements for the terrain and the area below. NASA has, for example, dedicated an entire mission to airborne. Operation IceBridgeTo measure the thickness of ice in Greenland or Antarctica, click here

The new mapping techniques are more precise, as a comparison of an Iceland’s Vatnajökull ice cap shows. The new map can be seen in the image below.
R. Millan et al., 2022

Scientists have developed a variety of new technologies. various techniquesTo Determine the volumeHowever, the uncertainty surrounding remote mountain glaciers is high.

We did something new compared to other studies. We used satellite imagery to map the glaciers’ speed. Glacier ice behaves as thick syrup when it’s thick enough. Two satellite images are used to measure how far the glacier ice is moving. We can also map its speed, which ranges from a few hundred feet to a mile per year. Although mapping the displacement of more that 200,000 glaciers was not an easy task, it produced a data set unlike any other.

Images show the velocity glacier ice across the globe.
R. Millan et al., 2022

This information, along with simple principles of ice formation, was used to determine the thickness of ice at each pixel on these satellite images. The ice sliding on its surface and its internal deformation are the main causes of the observed ice speed from space. The internal deformation is determined by its surface slope and ice thick. The slipperiness of its beds depends on the temperature at its bases, the presence or lack of liquid water, as well as the nature of the rocks and sediments beneath. Once we had established a relationship between ice speed, sliding, and ice thickness, we could calculate it.

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We analyzed 800,000.00 pairs of images from satellites of NASA and the European Space Agency to map the flow speed of all these glaciers.

As with any indirect method, these estimates are not perfect and will improve as more data is collected. However, we have made significant progress in reducing overall uncertainty.

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