Gulf Coast sea level rise stuck in overdrive

TULANE (US) — A new study shows the rate of sea level rise along the Gulf Coast has increased dramatically during the 20th century, as compared to the preindustrial millennium (600-1600 CE).

“Specifically, we have determined that the rate of sea level rise in the 20th century has been five times higher as a result of human-induced climate change,” says co-author Torbjörn Törnqvist, professor and chair of the Department of Earth and Environmental Sciences at Tulane University.

Sea level has risen more than 8 inches during the time period.

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Published in the journal Earth and Planetary Science Letters, the study, co-authored by postdoctoral research associate Shi-Yong Yu and graduate student Ping Hu, also reveals some relatively good news for the New Orleans area.

Though sea levels are rising at alarming rates, the ground 60 to 80 feet below is fairly stable.

“Our study shows that the basement underneath key portions of the Mississippi Delta, including the New Orleans area, has subsided less than one inch per century faster during the past 7,000 years than the more stable area of southwest Louisiana,” says Törnqvist.

“This difference is much lower than previously believed; most studies have assumed that a large portion of the Earth’s crust underneath the Mississippi Delta subsided much faster due to the weight of rapidly accumulating sediments in the delta.”

In other words, while the delta basement is in fact sinking, it’s sinking at extremely slow rates over vast geologic timescales. The seas will swallow the region long before anyone has to worry about the deeper ground below.

What do these findings mean for residents of coastal regions?

“Looking forward 100 years, our main concern is the continued acceleration of sea-level rise due to global warming, which is almost certain to happen and may amount to as much as three to five feet under the more pessimistic scenarios,” says Törnqvist.

“We can now show that accelerated sea-level rise has already been a larger factor in the past century than was previously believed.”

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