Going With the Flow
Do you like to play in the snow? You may not be thinking about snow at summer camp, but some places on Earth are always covered in snow.
What Landsat Sees
Landsat enables scientists to study some of the most dangerous and inaccessible places on our planet – such as the icy waters in the North Atlantic near Greenland and around Antarctica. These waters are home to most of the icebergs found on Earth. By studying these icebergs and the floating glacial ice areas that release them, scientists can gain a better understanding about ocean processes and influences on our changing climate.
Scientists use Landsat data to monitor icebergs forming off the coast of Antarctica. One iceberg, A-68 which broke free from the Larsen C Ice Shelf, began back in 2011 when scientists first notice a crack, or rift, in the ice shelf. Observed by Landsat 8’s visible and thermal bands, the crack could be seen gradually extending at first and then more rapidly in 2016 and early 2017. However, as Antarctica experiences months of polar darkness in the winter, Landsat’s visible sensor, the Operational Land Imager (OLI), could no longer track the position of the rift.
When there is no sunlight reflecting off the surface of the Earth, there is no light for the instruments to sense. Think of trying to take a photo in the dark. Instead, we can use Landsat’s other instrument, the Thermal Infrared Sensor (TIRS) to “see in the dark” by measuring the differences in surface temperature.
In the false-color image on the right, light blue and white colors in the image are the coldest surfaces, including the ice shelf and the thick iceberg. Purple colors reveal areas of thin sea ice, and regions of mixed water, ice, and snow called mélange. The yellow and orange colors indicate the warmest surfaces such as the open water between the shelf and berg.
Ice Ice Baby
If you had a snow day off from school or work, what would you do? Go sledding? Stay inside and drink hot chocolate? While a good snowstorm can be fun, snow gives us more than just snow days.
Snow can form glaciers in places where more snow piles up each year than melts. Each new snowfall compresses previous layers of snow causeing layers of snow to become denser and tightly packed. As the snow becomes even more compressed, it gradually compacts into increasingly solid ice called firn.
This snow pit in Antarctica shows more than 2m (6.5 ft) of accumulating snow compressed into layers of ice. Photo credit: Christopher Shuman
When ice gets thick enough, the firn grains fuse together creating a solid mass of ice. The glacier becomes so heavy that it begins to move downhill under the pressure of its own weight. Glacier flow is incredibly slow. Some move only a few centimeters per day; imperceptible to the human eye. But some glaciers, like the Muldrow Glacier in Alaska, can move 10s of meters per day.
This animation shows glaciers in Asia moving over a span of 11 years, from 1991 to 2002 using false-color images from Landsat 5 and 7. Moving ice is gray and blue; brighter blues are changing snow and ice cover. Image credit: NASA/JPL-Caltech/USGS/Earth Observatory
As glaciers bulldoze down the valley, debris is shoveled into a heap at the front edge of the glacier called a moraine. This image of the remote Grand Plateau Glacier shows a moraine near the coastline acting like a dam, trapping meltwater and forming a proglacial lake to the west.
The bright turquoise lake in the upper left of the image gets its color from fine-grained powder of silt and clay called glacial flour. Meltwater streams pick up these particles as the glacier grinds and pulverizes rocks along the valley floors and walls. Since the particles are so fine, they remain suspended in the water that absorb the shortest wavelengths of sunlight: the purples and indigos. Since water already absorbs the longer wavelengths of reds, oranges, and yellows, that leaves mainly blues and greens to get scattered back to our eyes as a turquoise color.
Snow Around the World
Have you ever seen a glacier? Have you ever hiked up a mountain to the snow line? Some glaciers and snow caps are covered with snow year round. For five decades, the Landsat satellites have been observing changes in snow and ice cover around the globe.
Let’s take a tour of some of these snow and ice-covered places.
This image shows the complete Randolph Glacier Inventory. The map includes some 198,000 glaciers that cover approximately 726,800 square kilometers (280,600 square miles) - all marked in blue.
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Columbia Glacier
The Columbia Glacier in Alaska is one of the most rapidly changing glacier in the world. It was relatively stable when the first Landsat satellite launched 1972. But starting in the mid-1980s, the glacier’s front began retreating rapidly, and by 2019 was 12.4 miles (20 kilometers) upstream.
Where a glacier meets the coast, it becomes a tidewater glacier. Its leading edge flexes and floats in the water, forming cliffs of ice that may be 60 meters (200 feet) high. The retreat of the Columbia Glacier contributes to global sea-level rise, mostly through iceberg calving. This one glacier accounts for nearly half of the ice loss in the Chugach Mountains.
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Greenland
About 80% of Greenland is blanketed by an ice sheet, also known as a continental glacier, that reaches a thickness of up to 2.1 miles (3.4 kilometers). Ice sheets are in motion, flowing under their own weight in all directions. Landsat satellite data has provided scientists with almost five decades of observations revealing stunning changes in Greenland’s glaciers.
Southeastern Greenland is home to Helheim, Fenris and Midgard glaciers. Helheim Glacier, one of the largest and fastest flowing of its kind in Greenland, has retreated approximately 4.7 miles (7.5 kilometers) since 1972, leaving a jumble of sea ice where its calving front used to be. To the east, Midgard Glacier has retreated approximately 10 miles (16 kilometers).
The glaciers appear brownish grey in this true-color Landsat 8 satellite (right). The color indicates that the surface has melted, a process that concentrates dust and rock particles and leads to a darker ice sheet surface. A darker surface means it absorbs more sunlight and gets warmer. Like the difference between wearing a white shirt or black shirt on a sunny day. When the ice surface absorbs more sunlight, the glacier melts faster.
Landsat 8 image from Aug. 12, 2019 (right) and a composite image from Landsat 1 scenes collected in September 1972 (left).
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Humboldt Glacier
In 1910, glaciers spanned an area of at least 10 square kilometers (4 square miles) in the mountainous region of northwestern Venezuela. Today less than one percent of that glaciated area remains, and all of it is locked up in one glacier.
A cold and snowy climate at high elevations is key for glaciers to exist in the tropics. But warming air temperatures, less snowfall, and more rain have contributed to their decline. Humboldt Glacier—Venezuela’s last patch of perennial ice—means that the country could soon be glacier-free.
The relatively recent changes to Humboldt are evident in this image pair, acquired on January 20, 1988, with the Thematic Mapper on Landsat 5 (left) and on January 6, 2015 with OLI (right). The images are false-color to better differentiate between areas of snow and ice (blue), land (brown), and vegetation (green).
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The outlet glacier of Vavilov Ice Cap, Russia
Glaciologists generally classify glaciers into two major types. In temperate areas, where summers are relatively warm and plenty of snow falls, warm-based glaciers dominate. This type slides easily, often slipping a few kilometers each year because water lubricates the ground and the base of the glacier.
In contrast, cold-based glaciers dominate in polar deserts—the cold, high-latitude areas that receive little snow or rain. This type of ice generally stays fixed in place, rarely moving more than a few meters per year.
In 2013, a cold-based glacier in the Russian High Arctic began sliding at a breakneck pace. After moving quite slowly for decades, the outlet glacier of Vavilov Ice Cap began sliding dozens of times faster than is typical. It went from moving 20 meters per year to 20 meters per day! The ice moved fast enough for the fan-shaped edge of the glacier to protrude from the ice cap.
Down by the Lake
Do you spend time at a lake in the Summer? Maybe camping, boating, or swimming? There are many lakes that were formed by glaciers including Lake Superior. Although glaciers move slowly, they are extremely powerful. They plow through the landscape like a bulldozer clearing everything in its path and gouging huge basins that become lakes.
Lakes are fun places to go year round. In the winter it’s fun to ice skate or ice fish on lakes that have frozen solid. In the summer, lakes are great for a refreshing swim, fish, boat and even water ski.
But in 2014, summer beachgoers and fishers got a wintery surprise on Lake Superior. Landsat 8 satellite captured this image on May 23rd at the start of Memorial Day weekend (an unofficial start of summer in the United States). By the second week of June, boaters, fishermen, and scientists were still capturing photos of ice chunks in the water.
Average water temperatures on all of the Great Lakes have been rising over the past 30 to 40 years and ice cover has generally been shrinking. (Lake Superior ice was down about 79 percent since the 1970s.) But chilled by persistent polar air masses throughout the 2013-14 winter, ice cover reached 88.4 percent on February 13 and 92.2 percent on March 6, 2014, the second highest level in four decades of record-keeping.
Today, glaciers are forming new lakes as they melt. In the largest-ever study of glacial lakes, researchers using a 30-year satellite data record have found that the volume of these lakes worldwide has increased by about 50% since 1990 as glaciers melt and retreat due to climate change.
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Postcards From Camp Landsat
Whatever you do for summer fun, wherever you go to relax, Landsat is there. Landsat data helps people manage, protect, and preserve some of your favorite places on Earth.
Collect all nine postcards from Camp Landsat continuing with Week 7: Ice & Climate !
The adventure continues at Camp Landsat with lots of fun and fascinating Landsat facts and activities.
