Earthshots: Satellite Images of Environmental Change

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» Svalbard, Norway
 

Fourteen tidewater glaciers flow into Hornsund Fjord, on the southern tip of Spitsbergen, the largest island of the Svalbard Archipelago, located about 700 kilometers north of mainland Norway in the Arctic Ocean. During the past few decades, these glaciers have retreated substantially.

In 1984, four glaciers formed a single terminus at the eastern end of Hornsund: Storbreen, Hornbreen, Svalisbreen, and Mendelejevbreen. By 2010, the glaciers had retreated far enough to each have a separate terminus into the fjord.

The main driver of this glacial retreat is increasing average temperatures. The melt season in Svalbard grew two weeks longer between 1912 and 2010.

The near-infrared imaging from Landsat clearly shows changes to these glaciers. The long record from Landsat is especially crucial to tracking the changes and projecting what may happen to the glaciers in the near future.

Map of the featured area.

The southern tip of Spitsbergen is called Sørkapp Land. Hornsund Fjord nearly divides Spitsbergen and Sørkapp Land into separate islands. Only an isthmus of ice separates the two. The narrowing isthmus could someday make Sørkapp Land a new island.

In fact, new islands have formed in other locations on the Arctic coasts of Europe and Greenland. In places where the bedrock is below sea level, sea water inundates the space left by retreating glaciers.

The isthmus between Spitsbergen and Sørkapp Land is rapidly thinning and recessing. In 1899–1900, the isthmus was 28 kilometers wide. According to one source, the isthmus was 6.2 kilometers wide as of 2013. Based on the 2019 Landsat image, and measuring the width of the isthmus using geospatial software, the isthmus has narrowed further to about 5 kilometers wide. This ice is grounded well below sea level, so when the ice melts, there will be a strait of open water between the two lands.

The same source estimates that the glaciers on the isthmus will retreat enough to make Sørkapp Land an island by 2030–2035. The isthmus decreased from 12.3 kilometers in 1990 to 6.2 kilometers in 2013, with a rate of decrease of about 270 meters per year. This annual decrease is close to matching that 5-kilometer measurement for 2019; in fact, the decrease is slightly faster than the source’s estimate.

With the launch of Landsat 9 expected in December 2020, Landsat satellites will continue monitoring the progress of these glaciers to see whether Sørkapp Land does indeed become a new island in the Svalbard archipelago.

“Isthmus” rhymes with “Christmas.”

Nearby on Spitsbergen is an extensive satellite ground station. Located just 1,200 kilometers south of the North Pole and established in 1996, the Svalbard Satellite Station, or SvalSat, was chosen for its extreme northern location. It is the only commercial ground station that can support polar orbiting satellites every time they orbit the Earth, about 14 passes per day. It’s an advantageous place for satellite control and downloading data.

When polar-orbiting satellites pass within range of the SvalSat station, data is downlinked directly from the satellite. The antennas receive data for about 15 minutes; then the fast-moving satellites pass out of range. Currently, the facility has more than 40 antennas to support several satellite missions.

SvalSat is a valuable member of Landsat’s International Cooperators network. SvalSat provides more contact opportunities with polar-orbiting satellites and more frequent download opportunities of data from Landsat as well.

Landsat data can be sent electronically from SvalSat to its primary archive at the USGS Earth Resources Observation and Science (EROS) Center in Sioux Falls, SD, in a matter of hours. Fiber optic cables under the ocean provide the data link from Svalbard to the satellite station at Tromsø, a city on the northern mainland of Norway, and then on to EROS. In this way, SvalSat is a valuable safety net for receiving Landsat data and providing flexibility during potential down times at other ground stations.

The Landsat 8 image showing SvalSat takes advantage of long hours of daylight in the summer at this extreme northern location by collecting sunlit nighttime images. This image was acquired at 8:10 p.m. local time in Svalbard.

A 10-m resolution image from the European Space Agency (ESA) Sentinel-2A satellite, which also sends data to SvalSat, shows the ground station in slightly higher resolution

References

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