Weather Watch

Climate change leading to higher tides in California. That means ‘nuisance flooding’

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California governor visits site of Northern California wildfire, says state “could literally burn up” if drought persists. Fire officials said Thursday that the Rocky fire had grown to 69,600 acres.

Last week, a group of esteemed colleagues (Dr. Ray Weymann, Walt Reil and Steve Kliewer) and I traveled to Caltech’s Jet Propulsion Laboratory (JPL) in Pasadena to receive a tour of the facility with JPL scientist Josh Willis. We also attended several presentations about climate change.

JPL was very active last week with the anticipated landing of NASA’s InSight lander Monday. This spacecraft will study the deep interior of Mars; InSight blasted off from Vandenberg Air Force Base on May 5.

One of the presentations that we attended was on the impacts of “nuisance flooding.” Nuisance flooding occurs at high tide that leads to public inconveniences such as road closures. Unfortunately, as sea level continues to rise, it is becoming progressively more common in the coastal regions.

In years past, this type of flooding only occurred during tempests when storm surge, storm runoff, high tides and large wind-generated waves combined to produce seawater intrusion — or during the “King Tides” (the very highest tides of the year).

Currently, a moderate El Niño event is brewing in the Pacific, and combined with global warming has contributed to warmer fall seawater temperatures. Usually, seawater temperatures along the Central Coast average around 58 degrees during the month of November. So far this November, the temperature average is 62 degrees.

When the water warms, it causes thermal expansion in the upper levels of the ocean.

Consequently, seawater levels can be several inches higher than those predicted in the tide tables. The observed water level has been about 5 inches taller than predicted tides at the Port San Luis Tide Gauge. In other words, the tide tables predict a 6.2-foot high tide Sunday at 10:25 a.m., but the actual tide will probably be above 6.7 feet.

The maximum tidal range along the Central Coast can reach from more than 2 feet below the mean low-water mark to more than 7 feet above it, for a tidal range of more than 9 feet. The highest tidal range that I know of is in the Bay of Fundy on the east coast of Canada, which can exceed 52 feet.

Dr. Willis told us that nuisance flooding had been worst on the East Coast that West Coast of United States, however, this may be changing. You see, another oceanographic cycle that can orchestrate changes in our weather, and sea level is a longer lasting cycle called the Pacific Decadal Oscillation or PDO.

While the El Niño–Southern Oscillation phase typically lasts from eight to 13 months, the PDO alternates between a warm phase (positive) and a cooler (negative) phase that can last a few years to decades. Unlike El Niño, which focuses on SST in the central equatorial region of the Pacific Ocean, the PDO is classified by seawater temperatures throughout the northern Pacific Ocean. According to Dr. Willis, the PDO appears to be shifting to a positive phase, which means higher sea levels due to thermal expansion along the west coast.

On the East Coast, rising sea levels have already become problematic. One community under threat is Norfolk, Virginia, home to Naval Station Norfolk. This base is the Navy’s largest naval station, with the largest concentration of U.S. Navy forces found anywhere in the world.

Six of the Navy’s 11 aircraft carriers are stationed there.

I was stationed in Naval Station Norfolk in the early 1980s at HSL-30 “Neptune’s Horsemen,” a training squadron for H-2 Seasprite helicopters. During the winter, it was cold and icy, and warm and humid during the summer. The entire area is as flat as a pancake, and much of the navy base sits on landfill. Not only is the sea level rising, but the landfill it’s built upon is gradually sinking.

The number of high tides at the Sewells Point Tide Gauge near the naval station that reached the “nuisance flood” level, where roads become impassable due to flooding, has steadily increased over the years.

The cost to upgrade the breakwaters, dry docks, piers where ships like aircraft carriers, submarines, cruisers and destroyers moor, electrical utility system, wastewater treatment facilities, buildings, hangers and on-base housing from the rising sea will cost taxpayers unfathomable amounts. How would sailors and civilians who live off base get to work even if the base was fortified from rising seas?

Today, many residents in the Hampton Roads area check tide charts before leaving for work to see if the main roads leading to the naval station will be open. Over the next 80 years, climate scientists are expecting about a 47-inch increase in sea level.

John Lindsey’s column is special to The Tribune. He is PG&E’s Diablo Canyon marine meteorologist and a media relations representative. Email him at pgeweather@pge.com or follow him on Twitter: @PGE_John.
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