oric ice cover on the North American Great Lakes and much slower than normal spring melt. The persistent and widespread ice has affected shipping transportation throughout the Great Lakes region. At one point, the Lake Superior ice cover was estimated to be nearly 95% with an average thickness of 22.6 centimeters (8.9 inches). Pressure ridges and ice motion can also cause plates of ice to buckle and stack, creating local ridges up to 1.5 meters (5 feet) thick in some places. Even though the ice has now started to melt, some areas of this year’s ice cover could last into June.
The abnormal thickness and extent of this year’s ice cover caused challenges to the ice breakers that allow shipping to and from ports such as Duluth Harbor. When cutting through very thick ice, it can take many hours to go a very short distance. At one point, as many as 70 ships were awaiting entry into Lake Superior, and the ships were being grouped together as escorted convoys to maximize ice-breaking efforts and allow safe passage.
These three Landsat 8 ”natural-color” (3-band composite) images show the Lake Superior area north of Duluth, Minnesota, in February and April 2014. The first image (February 16) shows the ice cover near its maximum. The second image (April 5) shows reduced ice coverage, along with an ice breaker channel that was created to allow ships to enter Duluth Harbor. The third image shows the remaining ice cover as of April 21.
Landsat imagery provides a consistent and repetitive view of the Earth’s surface and can be used to help monitor changing conditions over time.
Drought Conditions in California, USA April 24, 2014
After several consecutive years of below-normal precipitation, the U.S. state of California is preparing for its most severe drought emergency in decades. The current drought is due in part to decreased rainfall along with reduced winter snowpack in the Sierra Nevada mountain range. In 2013, California received less precipitation than any other year since it became a state in 1850. Water conservation efforts are already in place for many locations. For 2014, there is potential for major agricultural impacts, and the wildfire danger is expected to be unusually high.
These three images show a portion of California’s Central Valley (left side of the images) and the neighboring Sierra Nevada mountains as viewed by Landsat in February 2011, 2013, and 2014.
The decrease of winter snow cover can be seen in this progression of images. The reduction of available water supplies in the Central Valley is also indicated by the changing outlines of Folsom Lake, Camanche Reservoir, and other lakes and reservoirs in the images.
The 40-year archive of Landsat imagery is useful for monitoring the changing conditions of Earth’s surface areas through time.
Urban and Agricultural Change in Cairo, Egypt April 11, 2014
Egypt’s capital city of Cairo lies in the fertile Nile River Valley. Historically, Cairo and its agricultural areas have been geographically limited by natural desert borders, but these patterns are changing due to recent reclamation of surrounding desert land.
These two images were acquired by the Landsat satellites in 1987 and 2014. During this time period, Cairo’s population has increased from an estimated 6 million in 1986 to over 15 million in 2014.
The recent population growth has caused the city and its associated urban areas to expand into the surrounding desert, as seen in the second image. Within the main Nile River Valley, these two images also show an overall increase in developed urban area (grey/brown) versus previous agricultural land use (green).
As new urban and agricultural areas are being developed in the desert, they require diversion of water supplies from the main Nile River Valley. This expanded irrigation is indicated by the numerous bright green areas throughout the second image.
The Landsat data archive spans more than 40 years and provides a valuable record of changes on the Earth’s surface, including urbanization and agricultural land use change.
On March 22, 2014, a massive landslide occur