For people in the southeastern United States, and especially in Florida, who feel that annoying tidal flooding has sneaked up on them in recent years, it turns out to be true. And scientists have a new explanation.
In a paper published online Wednesday, University of Florida researchers calculated that from 2011 to 2015, the sea level along the American coastline south of Cape Hatteras rose six times faster than the long-term rate of global increase.
“I said, ‘That’s crazy!’” Andrea Dutton, one of the researchers, recalled saying when a colleague first showed her the figures. “ ‘You must have done something wrong!’ ”
But it was correct. During that period of rapid increase, many people in Miami Beach, Fort Lauderdale and other coastal communities started to notice unusual “sunny-day flooding,” a foot or two of salt water inundating their streets at high tide for no apparent reason.
. . .
Many people think the ocean works something like a bathtub, with sea level being the same all the way around. In reality, the ocean is lumpy, with winds, currents and other factors pushing water around to produce substantial variations in sea level from place to place.
Worldwide, the average level of the ocean is rising at a rate of about a foot per century, a consequence of the warming of the planet caused by the human release of greenhouse gases like carbon dioxide.
The excess heat trapped by those gases accumulates primarily in the ocean, and the seawater expands as it warms. Land ice is also melting into the sea because of the planetary warming, contributing to the rise, which appears to be accelerating over time.
But within that long-term trend, sea level in particular regions can sometimes rise more rapidly or more slowly than the global average. It can even fall for a few months or years.
