Wednesday, August 27, 2014
HOW CAN A LAGOON SINK? / NASA ANSWERS
VENICE EXPLAINED--When the polar ice melts, Las Vegas bookies—if asked—might take bets on what landforms on earth will sink soon below sea level. The Maldives are a good bet, but so is Venice, Italy, but waiting around to collect is the big catch.
The Maldives, are an archipelago in the Indian Ocean that averages five feet above sea level. And, of course, for years, we’ve heard Venice is awash and may join Atlantis.
To get to the bottom of all this NASA flies to the rescue with data on what’s keeping Venice afloat. We’ll save the Maldives for later.
Guest blogger William L. Stefanov, Science Applications, Research and Development Department, Jacobs NASA, Johnson Space Center explains “...the City of Venice, Italy, is known for its architecture, history, romance, and, of course, the canals that serve as major thoroughfares through the urban area. The canals and bridges are the human overprint on the Lagoon of Venice, a marshy body of water along the Adriatic Sea that contains the 117 islands upon which the city is built. In addition to forming the base of the city of Venice, the Lagoon is a critical part of the Mediterranean wetlands ecosystem, recognized by international treaty as a Ramsar site.
“Like many coastal regions, the Lagoon of Venice, together with the city of Venice and the environmentally sensitive wetlands, is subsiding into the Adriatic Sea, creating flood risks for Venice and major damage to the wetlands.
“A narrow barrier island protects the Lagoon of Venice from storm waves in the northern Adriatic Sea, and breakwaters protect inlets to the lagoon. Red tiles on the roofs of Venice contrast with the grays of the sister city of Mestre, and the cities are joined by a prominent causeway.
“What appears to be another causeway joining the island to the airport (top right) is actually the combined wakes of many boats and water taxis shuttling between them. Small, bright agricultural fields on well-drained soils (top left) contrast with the darker vegetation of back-bay swamps, where fishing is a popular pastime.
“The water is turbid in the northern half of the lagoon, the result of heavy use by watercraft and of dense urban populations on the shores. This turbidity and other issues of environmental concern led to the creation in 2002 of the Atlas of the Lagoon (Atlante della laguna), which was set up to document environmental conditions and to track changes.
“Today, the Atlante della laguna is available online (in Italian) and provides a comprehensive collection of interpretive maps and imagery—including astronaut photographs from the International Space Station...”
This astronaut photograph (ISS039-E-19482) was acquired on May 9, 2014, with a Nikon D3S digital camera using a 400 millimeter lens, and is provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit, Johnson Space Center.