Oct 17, 2016

Sea Level Rise Upping Ante On ‘Sunny Day’ Floods

Key West, FL
USA
by
Benjamin Strauss
,
Climate Central
A perigean spring tide floods Highway 80, the only road to Tybee Island, Ga., June 4, 2016. Photo: Stephen B. Morton/The New York Times
A perigean spring tide floods Highway 80, the only road to Tybee Island, Ga., June 4, 2016. Photo: Stephen B. Morton/The New York Times

Parts of the Atlantic Coast are still recovering from the onslaught of Hurricane Matthew, but even more flooding is on the way as local tides will reach some of their highest points of the year. With little chance to recover between events, coastal cities are facing a constant reminder that climate change has already tipped the scales toward more frequent and bigger floods.

When the earth, moon, and sun are in perfect alignment, gravity pulls the oceans to their highest tides, often afflicting coastal communities with minor or nuisance flooding that can close roads, inundate local businesses, erode beaches and cause sewage overflows. And as global warming accelerates sea level rise, these floods — often called sunny day floods — are increasing; in many locations they’re occurring 10 or 20 times a year.  

This week, points along the Atlantic and Gulf Coasts will be experiencing those highest of high tides — commonly known as king tides. But added to this natural tidal cycle are several inches of water brought on from an unnatural source: us. Rising temperatures over the past century — mostly fueled by our carbon emissions from fossil fuels — have caused sea levels to rise, which has made high tides even higher than they used to be in most places. And with sea level rise accelerating, this week’s king tides, and the floods they will deliver, give us a preview of what everyday water levels will soon be like because of global warming.

While flooding from king tides, and similar floods from storms or high winds, aren’t usually as severe as the ones doled out by hurricanes and tropical storms, they happen much more frequently. Recent research attributes about 6 inches of the world’s sea level rise that has occurred since 1900 to human-caused global warming. And given current levels of carbon emissions, that rate is expected to accelerate. Scientists project that sea level rise could surpass 3 feet by the end of the century. At the local level, sea level rise amounts to higher water lines during high tides, so local thresholds for minor floods are surpassed more frequently now than in the past.