Mountain glaciers may hold less ice than previously thought

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The new mapping method is more accurate, as the comparison of Iceland’s Vatnajökull ice caps shows. The image on the left is a new map. credit: R. Millan et al. , 2022

Mountain glaciers are an essential source of water for almost a quarter of the world’s population. However, it was notoriously difficult to figure out how much ice they hold and how much water is available when glaciers shrink in a warming world.

In a new study, scientists have mapped velocities of over 200,000 people Glacier To get closer to the answer.They have found estimates of the amount of ice in widely used glaciers. It may be off by about 20% In terms of how much the Earth’s glaciers outside the Greenland and Antarctic ice sheets can contribute sea ​​level rise..

Matthew MaurigemExplain why, a leader in ice sheet modeling and a co-author of research New results It warns areas that rely on the glacier’s seasonal snowmelt water, but are rarely registered in the overall picture of sea level rise.

1. If a mountain glacier holds less ice than previously believed, what does that mean for those who depend on glaciers for water?

Worldwide, approximately 2 billion people rely on mountain glaciers and snow as their primary source of drinking water. Many also rely on glacier water for hydropower and agriculture, especially during the dry season. However, the vast majority of glaciers around the world are losing more mass than they can get each year as the climate warms. Will disappear slowly..that is Seriously impacts these populations..

These communities need to know how long glaciers will continue to supply water and what they can expect when glaciers disappear and become ready.

In most places, we found significantly less total ice volume than previous estimates showed.

For example, in the tropical Andes from Venezuela to northern Chile, glacier ice was found to be about 23% less than previously believed. This means that the downstream population has less time to adapt to climate change than planned.

Even in the Alps, where scientists have many direct ice thickness measurements, it turns out that glaciers may be 8% less than previously thought.

The big exception is Himalayan. We calculated that these remote mountains could have 37% more ice than previously estimated. This spends some time on communities that depend on these glaciers, but does not change the fact that these glaciers are melting due to global warming.

Policy makers need to look at these new estimates and revise their plans.This study does not provide new forecasts for the future, but it does. Better explanation What the glacier and its water supply look like today.

2. How do these discoveries affect future estimates of sea level rise?

First, it is important to understand that melting glaciers are the only cause of rising sea levels as the climate warms.About one-third of today’s sea level rise Thermal expansion Sea — As the sea warms, the water expands and occupies more space.The other two-thirds Shrinking mountain glaciers and ice sheets..

If all glaciers except Greenland and the large ice sheets of Antarctica melt completely Sea level rises about 10 inches Instead of 13 inches. Given the size of the ocean, this may sound like a big difference, but things need to be taken into account.The complete collapse of the Antarctic ice sheet will contribute 190 feet To the sea level and Greenland ice sheet Contribute 24 feet..

The 3 inches we are talking about in this study do not question the current predictions of sea level rise.

3. Why is it so difficult to keep track of the amount of ice in a glacier? And how was your study different?

You may be surprised at how unclear some of the basic features of distant mountain glaciers are.

Satellites have changed our understanding of glaciers since the 1970s, providing increasingly clear images of glaciers. Glacier location and surface area.. However, satellites cannot see “through” the ice. In fact, for 99% of the world’s glaciers, ice thickness cannot be measured directly.Scientists have spent a lot of time mapping Greenland and Antarctic ice sheets And the terrain below it, and we have much more detailed volumetric readings there. For example, NASA dedicated an entire aerial mission. Operation ice bridgeCollect measurements of ice thickness in Greenland and Antarctica.

Scientists came up with Various techniques To Determine the volume Glacier, but remote uncertainty Mountain glacier It’s quite expensive.

I did something different from my previous research. We used satellite images to map glacier velocities. Glacier ice behaves like a thick syrup when it is thick enough. You can use the two to measure how much ice is moving Satellite image Then map that speed. This can be a few feet to about a mile a year. Mapping glacier displacements in excess of 200,000 has never been an easy task, but it has created a dataset that no one has ever seen.

Using this new information about ice velocity and the simple principles of ice deformation, we determined the thickness of ice at each pixel of these satellite images. In short, the speed of ice we observe from space is due to the ice sliding on its bed and its internal deformation. Internal deformation depends on the slope of the surface and the thickness of the ice, and the slipperiness of the layer depends on the temperature of the ice at the bottom, the presence or absence of liquid water, and the nature of the sediment or rock beneath it. .. Once you have calibrated the relationship between ice velocity and slippage, you can calculate the thickness of the ice.

To map the flow velocities of all these glaciers, we analyzed 800,000 pairs of images collected by satellites from the European Space Agency and NASA.

Of course, like other indirect methods, these are not perfect estimates and will improve further as more data is collected. But we have made a lot of progress in reducing overall uncertainty.

The new Atlas has discovered that Earth’s glaciers have less ice than previously thought.

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Quote: Mountain Glacier is a previous idea taken on February 8, 2022 from https: // (February 8, 2022) May hold less ice than a day)

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Mountain glaciers may hold less ice than previously thought

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