The city of New Orleans and its surrounding areas are rapidly sinking every year, according to a new airborne radar study conducted by NASA and several universities.
The subsidence rate for the Louisiana city is occurring at higher rates than previous records, all of which have been measured by lower-resolution and non-spatially exclusive radars, researchers said.
The new study, which spanned June 2009 to July 2012, found that the highest subsidence rate was up to 2 inches a year in the city. This was observed near the Mississippi River in industrial areas such as Michoud and Norco.
Other increasing subsidence rates were detected in Metairie and Bonnet Carré Spillway, where water levels spiked about 1.6 inches per year.
What's causing the rapid subsidence? Scientists said both naturally occurring geologic events and human-caused processes were triggering it.
The study cites groundwater pumping and surface water pumping as the main human-induced trigger of the phenomenon.
The factors also include faulting; deposited sediments affecting the crust of Earth; withdrawal of gas, oil, and water; shallow sediments compacting; and continuous land movement from glaciers.
The state of Louisiana has been among areas in the United States hit hardest by climate change. The government has allocated $48 million in funding to transfer the community of the sinking Isle de Jean Charles to drier land.
However, New Orleans isn't the only area continuously sinking. Scientists said Washington D.C. is also sinking and could even drop to at least 6 inches in the next hundred years.
At least 10,000 refugees from the Marshall Islands, which have already sunk to more than 6 feet above sea level, have transferred to Arkansas to escape the dire conditions at home. If average global temperatures rise by another 6 degrees Fahrenheit by 2100 and cause sea levels to rise, about 20 to 31 million Americans could be affected. This is higher than the 13 million figure estimated by a previous University of Georgia study.
"People need to understand that the planet is not only changing, it's changed," said scientist Tom Wagner.
Meanwhile, scientist Cathleen Jones of NASA's Jet Propulsion Laboratory said the findings of the study could be used by agencies to effectively implement actions to reverse and remediate the effects of subsidence.
The details are published in the Journal of Geophysical Research.
