NASA-USGS provide near-real-time view of global ice movement

NASA-USGS provide near-real-time view of global ice movement

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global ice movement
The texture on the surface of flowing ice, such as Heimdal Glacier in southern Greenland, allows Landsat 8 to map nearly all the flowing ice in the world. Credits: NASA/John Sonntag

As concerns over the melting poles, rise in seal levels and the possibility of Donald Trump’s move to cut NASA funding for earth observation research ring alarm bells across the world, the agency has further bad news. Monitoring of global ice movement reveals sea waters are rising at a global average rate of 3.3 millimeters per year. Evidences strongly suggest that loss of ice from glaciers and ice sheets are the primary contributor to sea level rise over the past three decades.

With imagery and data from Landsat 8, a joint mission of NASA and the US Geological Survey, scientists are providing a near-real-time view of every large glacier and ice sheet on Earth. A group of scientists from the National Snow and Ice Data Center (NSIDC), the University of Alaska–Fairbanks, the University of Bristol, and the Jet Propulsion Laboratory (JPL) are now collaborating on a unique project called the Global Land Ice Velocity Extraction (GoLIVE) to better understand how ice flow is changing worldwide.

Global ice movement

The freely available data from Landsat 8 on changes in ice flow is combined with the data on ocean and atmospheric changes to determine the exact level of rise in oceans, what causes ice masses to change and how much ice will flow into the ocean. Researchers hope to monitor the changes every few weeks and at scales as small as 5 meters. This will be a very handy tool to provide critical information to coastal communities that are usually most impacted by rising oceans.

With measurements of what the seasonal shifts do to glacier speed, scientists can extrapolate what will happen to those glaciers as global temperatures continue to climb, she said. With fast-moving glaciers ending in the ocean, these studies can help scientists estimate how much new ice and water enter the Arctic Ocean. That new water can have both global and local impacts, changing the local ecosystems and ocean flow patterns and raising sea level.

global ice movement
The globes show how many times Landsat 8 passed over a given icy parcel in 2015 alone. Credits: NASA Earth Observatory/Joshua Stevens

The preliminary findings of the project was unveiled at 2016 fall meeting of the American Geophysical Union taking place from December 12 to 16.

The satellite-based approach is particularly valuable in remote landscapes, where ground- and airplane-based observations are expensive, dangerous, and intermittent. In Alaska and Canada’s Yukon Territory, for instance, glaciers are so remote that changes can go unnoticed for months until a pilot flies over the region and reports disrupted ice.

Continuous measuring of the ice flow can help scientists identify a surge immediately or follow large seasonal swings in tidewater glaciers, which is a necessity for identifying long-term trends.

Landsat 8 to the rescue

Interestingly, automation has been the key to this ice velocity mapping effort. Landsat 8 collects roughly 700 sunlit images of the planet every day. Over the course of 16 days, it observes the entire land surface of Earth in multiple visible and infrared wavelengths. This means scientists can view changes in the same spot on Earth every 16 days (or 32, 48, 64, etc., as cloud cover allows).

Previous Landsat satellites often did not have the ability to collect frequent data over remote sites like the poles. The Landsat 8 sensors are also far more sensitive and enable it to distinguish far more subtle differences in shading and surface texture. To map the ice flow, the GoLIVE team has created a software that can monitor the subtle features on the surface, like bumps or a dune-like patterns as they flow toward the ocean.

global ice movement
A representation of ice velocities in Antarctica on a Landsat 8 image acquired in 2015. Credits: NASA Earth Observatory images by Joshua Stevens

In the three year period from 2013 to 2016, Landsat 8 collected thousands of images from Antarctica alone. As many as 150 to 200 images were collected over the brightest yellow and green areas, while purple areas had just a handful of useful images because of frequent cloud cover and fewer orbital passes. Due to the nature of the satellite’s polar orbit, areas in the far north and south can be imaged more frequently (when there is sunlight). Almost 2,000 cubic kilometers of ice flows into the Southern Ocean from Antarctica each year.

Tracking the changes in speed in Antarctica is crucial because of the sheer size of the ice sheet and its potential to contribute to future changes in sea level. Almost 2,000 cubic kilometres of ice flows into the surrounding ocean each year.

global ice movement
The flow of ice is dramatically faster at Greenland’s Heimdal Glacier in June 2016 (left), compared to October 2016 (right). Credits: NASA Goddard’s Scientific Visualization Studio/Cindy Starr

Similarly in Greenland the new database can help scientists study the movements of more than 240 glaciers. With it is known that Arctics are melting faster, several glaciers in northwest Greenland were to have accelerated speed in the last few years. While most glaciers speed up in the warmer summer months, it has been found several that slow down dramatically in the mid- to late-summer. The Heimdal Glacier in southeast Greenland, for example, can move more than 10 meters per day in early summer, then drop to less than 6 meters per day by August or September.

The team has also mapped the glaciers in Karakoram and other high mountain ranges in Asia, where they found that glacier flow is highly erratic with some glaciers, and others remain relatively unchanged over decadal timescales.

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