Water at record-breaking levels along Southeast and Gulf Coasts in US

Satellite measurements since 1900

The authors identified the specific causes of the acceleration by analyzing field and satellite measurements going back to 1900.

“We systematically investigated the different causes, such as vertical land motion, ice-mass loss, and air pressure, but none of them could sufficiently explain the recent rate,” said Noah Hendricks, co-author and undergraduate student in Dangendorf’s team at his former institution, Old Dominion University in Norfolk, Virginia.

“Instead, we found that the acceleration is a widespread signal that extends from the coasts of the Gulf of Mexico up to Cape Hatteras in North Carolina and into the North Atlantic Ocean and Caribbean Seas, which is indicative of changes in the ocean’s density and circulation.” 

This entire region, known as the Subtropical Gyre, has been growing over the last 12 years primarily as a result of altered wind patterns and ongoing warming. Sea levels rise as a result of the requirement for additional space created by warmer water masses.

According to the researchers, the recent acceleration resulted from the unfortunate coincidence of signals related to human-caused climate change and a high in weather-related variability that lasted for several years. They concluded that in the upcoming decades, the rates would probably return to the more reasonable range suggested by climate models.

“However, this is no reason to give the all clear,” said Torbjörn Törnqvist, co-author and the Vokes Geology Professor in the Department of Earth and Environmental Sciences at Tulane. “These high rates of sea-level rise have put even more stress on these vulnerable coastlines, particularly in Louisiana and Texas where the land is also sinking rapidly.” 

Study abstract:

While there is evidence for an acceleration in global mean sea level (MSL) since the 1960s, its detection at local levels has been hampered by the considerable influence of natural variability on the rate of MSL change. Here we report an MSL acceleration in tide gauge records along the U.S. Southeast and Gulf coasts that has led to rates (>10 mm yr−1 since 2010) that are unprecedented in at least 120 years. We show that this acceleration is primarily induced by an ocean dynamic signal exceeding the externally forced response from historical climate model simulations. However, when the simulated forced response is removed from observations, the residuals are neither historically unprecedented nor inconsistent with internal variability in simulations. A large fraction of the residuals are consistent with wind-driven Rossby waves in the tropical North Atlantic. This indicates that this ongoing acceleration represents the compounding effects of external forcing and internal climate variability.