Sea level is rising along US Atlantic coast, say environmental scientists

Dec 10, 2009
Professor Ben Horton (University of Pennsylvania) collects salt marsh sediment in North Carolina. Credit: University of Pennsylvania

An international team of environmental scientists led by the University of Pennsylvania has shown that sea-level rise along the Atlantic Coast of the United States was 2 millimeters faster in the 20th century than at any time in the past 4,000 years.

Sea-level rise prior to the 20th century is attributed to coastal subsidence. Put simply, land is being lost to subsidence as the earth continues to rise in response to the removal of the huge weight of ice sheets during the last . Using sediment cores from the U.S. Atlantic coast, researchers found significant spatial variations in land movement, with the mid-Atlantic coastlines of New Jersey, Delaware and Maryland subsiding twice as much as areas to the north and south. Coastal subsidence enhances sea-level rise, which leads to shoreline erosion and loss of wetlands and threatens coastal populations.

Researchers corrected relative sea-level data from tide gauges using the coastal-subsidence values. Results clearly show that the 20th-century rate of sea-level rise is 2 millimeters higher than the background rate of the past 4,000 years. Furthermore, the magnitude of the sea-level rise increases in a southerly direction from Maine to South Carolina. This is the first demonstrated evidence of this phenomenon from observational data alone. Researchers believe this may be related to the melting of the and ocean thermal expansion.

"There is universal agreement that sea level will rise as a result of global warming but by how much, when and where it will have the most effect is unclear," said Ben Horton, assistant professor in the Department of Earth and Environmental Science at Penn. "Such information is vital to governments, commerce and the general public. An essential prerequisite for accurate prediction is understanding how sea level has responded to past climate changes and how these were influenced by geological events such as land movements."

The study provides the first accurate dataset for for the U.S. Atlantic coast, identifying regional differences that arise from variations in subsidence and demonstrate the possible effects of ice-sheet melting and thermal expansion for rise.

The results appear in the Dec. 1 issue of the journal Geology.

Source: University of Pennsylvania (news : web)

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NotAsleep
3 / 5 (2) Dec 10, 2009
"Put simply, land is being lost to subsidence as the earth continues to rise in response to the removal of the huge weight of ice sheets during the last glacial period."

The earth is "rising"? What? Are they trying to say that ice-age ice, which has melted into the ocean, is pushing up the land like a popped zit? If so, how does this correlate to lost land along the eastern sea coast?

"Coastal subsidence enhances sea-level rise, which leads to shoreline erosion and loss of wetlands and threatens coastal populations."

So a subsiding shoreline causes sea-level rise which leads to a subsiding shoreline... oh no, infinite loop!
Parsec
2.3 / 5 (3) Dec 10, 2009
Actually I think that I saw the fact that the continents are rising as a result of shedding their ice caps in my son's 7th grade science book. Imagine the continents floating in a sea of softer mantle. They lose weight and as a consequence float higher. The mantle is so viscous that even 10,000 years after losing their ice caps they are still rising.

So coastal sea level gauges have to account for the rising level of the land to accurately measure sea level changes.

This is hardly an infinite loop my NotAsleep friend. It might be best if you returned to your nap.

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