The east coast of the United States is slowly but steadily sinking into the sea. This is the result of a recent study which took a variety of factors into account when determining the continuous sinking of the eastern seaboard.
(From Forbes / by Trevor Nace) –This will result in more frequent and severe flooding events in the future as the sea encroaches upon coastal communities and homes. This is all the more relevant as Hurricane Irma inundates the southeast coastline with rising storm surge.
On average, the eastern seaboard sees 3 mm per year of higher seas, according to a recently published article in Nature’s Scientific Reports. The slow flooding of coastal communities has resulted in flooding during sunny and calm days. This flooding causes regular damage to houses, commercial buildings, and roads.
There are three primary reasons why the east coast of the United States is seeing higher relative seas. Two of which involve sinking of the east coast into the sea.
The first reason is due to post-glacial isostatic rebound. This is a fancy term for a simple process. During the last glaciation, much of the northern United States and Canada was under immense ice sheets. This ice weighed down on the continental crust, causing it to sink into the partially molten upper mantle. Imagine you’re in a swimming pool with a floating noodle and you push down on the center of the noodle (ice weighing down the continent).
On either side of where you pushed down, the noodle will pop up a bit to compensate for the load. This same process happens on Earth when it experiences a large heavy load such as a glacier. So the glaciers on the North American continent caused the east coast to pop up a bit due to the load. However, once the glaciers melt, the weight on the continent is removed and the edges fall back down. Similar to if you removed your hand from a noodle you’d notice the popped up portions on either side of your hand will move downward. This gradual and slow rebounding or lowering of the continent after being pushed up from a glacier is called isostatic rebound. This has resulted in the east coast of America to slowly but steadily sink relative to the Atlantic Ocean.