For example, in October 2017 in Virginia and in other locations, Hurricane Jose, which never made landfall but churned hundreds of miles off the U.S. coast, contributed to king-tide flooding. Off Sewells Point near Norfolk, the water rose 0.73 feet (.22 meters) above what the National Oceanic and Atmospheric Administration considers minor flood stage there.
Such situations are becoming increasingly common and more troublesome. In Florida, the number of king tides has soared 400 percent between 2006 and 2016. And during summer of 2019, Miami set multiple high-tide records in late July and early August.
Why the increase? Although there are many reasons why king tides are driving water further inland, none is more worrisome than climate change. As Earth warms, ice melts and the temperature of the ocean gets hotter. When that happens, water expands and rises.
"The king tides are garnering more attention now due to the derivative effects of sea level rise, and coastal land subsidence due to the draining of subsurface aquifers for drinking water in many coastal regions," Loftis says.
Brian McNoldy, a scientist at the University of Miami's Rosenstiel School of Marine and Atmospheric Science, says seasonal effects, such as the amount of precipitation, also play a role. In addition, when trees and plants begin to shut down for the winter and shed their leaves, they cannot absorb as much rain runoff as they do in the spring and summer. As a result, the increase runoff contributes to flooding during king tides.
Although wind doesn't have a direct impact on king tides, it does play a role. In South Florida, McNoldy says, a persistent onshore wind increases the water level up to a foot (.03 meters) on top of the regular astronomic tides. The impact on communities can be devastating. Right after Hurricane Irma blew through in 2017, king tides flooded some neighborhoods of Anna Maria Island, Bradenton Beach and parts of South Florida for several days, creating unease in an already ravaged area.