2023-05-04 09:38:48
The country’s Atlantic coastline is sinking by several millimeters a year, exacerbating the effects of rising seas, according to a new study.
Climate scientists already know that the East Coast of the United States might experience regarding 30 cm of sea level rise by 2050, a catastrophic event in itself. However, researchers have only just begun to assess it in detail “hidden vulnerability”which makes the situation much worse: the coastline in the eastern part of the country is also sinking.
Due to land subsidence and rising ocean levels, the area can become dangerous for both people and the ecosystem.
According to new research published in the journal Nature Communications, the Atlantic coast, home to more than a third of the US population, is sinking by several millimeters every year. In Charleston, South Carolina, and the Chesapeake Bay, it might reach five millimeters. In some areas of Delaware, the increase is double that.
Adding an additional five millimeters (or more) of coastal subsidence to five millimeters of annual sea level rise results in a relative sea level rise of 10 millimeters. Cities on the Atlantic side of the country are already plagued by persistent flooding, which will only get worse as the coastline sinks and the seas rise. However, this type of subsidence data is still not considered in coastal risk assessment.
There are several reasons for this phenomenon
The main cause of dramatic land subsidence is over-extraction of groundwater, which causes the soil to collapse. Oil extraction also contributes to subsidence, which is particularly problematic in the Houston-Galveston area of Texas.
Although they know that the US coastline is sinking, scientists have so far had little data to show local differences in the rate of subsidence. The phenomenon varies significantly even within short distances, which is due to differences in the underlying geology and nearby human activities. For their latest research, Shirzaei and the study’s lead author, Leonard Ohenhen, used data from a highly sensitive satellite that sent radar signals back to Earth and then analyzed the bounce to determine coastal deformation. The analysis covered the years between 2007 and 2020, along 3,500 kilometers of Atlantic coastline.
The researchers recorded particularly intense subsidence in agricultural areas, where groundwater is extracted to feed crops, which in turn are more vulnerable to flooding as altitude falls. They also found that most Atlantic coastal cities, including Boston and New York, are sinking at more than 3 millimeters per year. A drop in sea level destabilizes surface infrastructure, such as buildings and roads, as well as underground pipes and cables.
Also, a big problem is that the East Coast is one of the fastest growing areas in the United States in terms of population. More population means people use more water and the rate of land subsidence will increase.
Because of the rise and fall of the seas “spirit forests” also occur on the coast of the Atlantic Ocean. The salt water seeps into the groundwater and kills the trees, whose roots normally compact the soil. “The first thing we need to do is to ensure as much as possible that our wetlands remain healthy” says Natalie Snider, vice president of the Environmental Defense Fund’s Climate Resilient Coasts and Watersheds program, who was not involved in the new in study.
The new, accurate satellite data used in the research will also help scientists and policymakers better understand subsidence: not only where, but also at what rate. In this way, they will also be able to determine how the process might be stopped or at least slowed down.
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