In this audio lecture, David Vaughan explains how we can use satellites to measure the effect that melting mountain glaciers have on sea level rise.

Mountain glaciers flow downslope because they accumulate mass from ice in their upper portions from precipitation and wind-blown snow, and they ablate (melt) in their lower portions.

Glaciers can be mapped using both optical imagery and SAR. However, optical imagery is weather dependent and SAR can be done regardless of weather conditions.

Surging glaciers are glaciers that are subject to cyclical flow instabilities. They have short, semi-periodical periods of rapid velocity where they can advance dramatically. They can flow between 10 to 100 times faster than normal glaciers.

Surging glaciers can be dangerous. For example, in 2016, a surging glacier in Tibet unleashed an avalanche of 90 million cubic yards of ice and rock, which killed 9 herders, more than 100 yaks and 350 sheep.

Surging glaciers can also be used to predict how large glaciers on Greenland and in the Antarctic will behave, and this helps scientists to predict more accurately sea level rise.

Glacial retreat is the process by which glaciers melt faster than precipitation can replace the melted ice.

Glaciers store 75% of the world’s fresh water, which makes glaciers form the largest reservoir of fresh water on the planet. The glaciers in the high-mountain region of Asia are the source of 10 major river systems. They provide freshwater for over 1.3 billion people in Asia, which makes up nearly 20% of the world’s population.

The Gangotri Glacier is one of the largest glaciers in the Himalayan Mountains and is one of the main sources of water for the Ganges River.

With such a large portion of the world’s population depended on water from glaciers like Gangotri, changes in the size and flow of glaciers can seriously disrupt society by changing the amount of water that arrives downstream.

As well as providing freshwater, glaciers make provide good conditions for growing crops. When glaciers retreat, they deposit materials such as rock, gravel and dirt. This is known as till and it provides very fertile soil for farming.

Glaciers are important indicators of global warming and climate change, as they act as early indicators of climate changes that will have a more delayed impact on other parts of the cryosphere. 

Melting glaciers are the most visible evidence of global warming today. As well as contributing to rising sea levels, widespread loss of glaciers will alter climate patterns in complex ways, for example by altering the Earth’s albedo.

Glacial ice can range in age from several hundred to several hundreds of thousands of years, making the data that is contained it glacial ice cores very important for climate research. The partially trapped air bubbles in the ice cores reveal past atmospheric composition, temperature variation and types of vegetation. This helps scientists work out how and why the climate has changed in the past and how it might change in the future.

In addition, large freshwater melt events change the ocean ecosystem by changing the THC (Thermo Haline Circulation) of the oceans by pushing heavier salt water down and altering ocean currents. Additionally, organisms such as corals depend on saltwater for survival and may not be able to survive a change to a freshwater habitat.

For more than a decade, satellite data have documented that Asia’s high-mountain glaciers and losing mass due to melting. Scientists needs to understand what regulates glacial flow speed to predict how meltwater will affect the region’s supply of freshwater in the future and how meltwater adds to sea-level rise.

ESA’s Glaciers CCI project is focused on establishing a consistent framework for glacier identification and to enhance the integrity of data sets. To do this, they are using data from both optical and microwave satellites, space-borne altimeters and digital elevation models.

It will measure the following characteristics of glaciers:

-      Glacier area: mapping the area and outlines of glaciers

-      Elevation change: tracking the elevation of glaciers over time

-      Surface velocity: tracking how quickly the glacier moves

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Featured Educator:

• Professor David Vaughan

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