The average rise in global sea level has been fairly steady over the past few decades, at about 3.2 millimeters per year. However, a huge increase in this rate may be just around the corner for California.
Willis has been an authority on sea-level changes for years. Willis noted that the rate of sea-level rise along the California coast has been notable over the past 20 years because it's been much slower than the rate of global sea level rise.
Willis and other noted oceanographers believe this is because, for the past 15 to 20 years, the Pacific Ocean has been in a cold phase of the Pacific Decadal Oscillation, or PDO.
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Think of the PDO as a prolonged version of its much better known little brother and sister: El Niño and La Niña. Generally, the PDO waxes and wanes approximately every few decades — unlike the El Niño and La Niña cycle, which may last only one or two years.
Lower-than-normal sea-surface temperatures in much of the Pacific Ocean characterize the cool phase of the PDO, not just the parts near the equator. When water cools, it contracts.
During strong La Niña events, when seawater temperatures along our coastline are colder than normal, sea levels can actually be several inches lower than those predicted in the tide tables.
This is because of the thermal contraction of the upper levels of the ocean. However, when the ocean warms, it relentlessly expands.
In an ominous sign, we may be shifting back to a positive, or warm, phase of the PDO.
“If that's the case, California may be looking at 20 years of sea level rise that is two to three times faster than the global rate,” Willis said. “If that happens, we could see a rise of as much as 1 centimeter per year for the next decade. One centimeter doesn't sound like much, but for each centimeter of rise, most beaches lost 3 feet of width. So it can be devastating.”
The effects of rising seas are amplified when combined with waves generated by high winds, storm surges, storm runoff and tides.
This unfortunate circumstance will not only put hundreds of thousands of Californians who live along the coastline in harm’s way, but also millions — if not billions — of other folks who live along the populated coastlines of our world.
To make matters worse, global warming caused by the relentless release of greenhouse gases by our own activities will continue to intensify this dire situation if we continue along this ill-fated path.
Adm. David Titley, a former oceanographer and navigator of the U.S. Navy who is a professor at Penn State and the founding director of Penn State’s Center for Solutions to Weather and Climate Risk, said it best: “Over the years, scientific findings on climate change have built to the point where we simply cannot afford to ignore them. And this is true no matter what your politics might be. The climate doesn’t care about politics.”
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