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Sea Level Rise Could Come Much Sooner Than You Think

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A flood in Garden Grove in 1971. | Photo: Orange County Archives, some rights reserved

It was just over a week ago that we reported on a study of melting of the West Antarctic Ice Sheet, which seems to be adding more water than we'd expected to the world's oceans. According to that study, melting off the West Antarctic is expected to boost sea levels by about a meter by the end of this century, bringing the total increase in sea level from all sources to two meters — six and a half feet — by 2100.

As it turns out, that recent news might already be obsolete, and far too optimistic. In a presentation at the Risk Management Society's RIMS 2016 conference in San Diego April 12, a top scientific official with the National Oceanic and Atmospheric Administration said that recent, as-yet-unpublished data from Antarctica suggests that sea levels could rise three meters — almost ten feet — by the middle of the century.

Margaret Davidson, NOAA’s senior advisor for coastal inundation and resilience science and services, told conference attendees that "the latest field data out of West Antarctic is kind of an OMG thing.” Davidson said that data shows sea level rise could reach three meters by 2050 or 2060, a much steeper rise happening far sooner than even the most catastrophic scenarios currently available in peer-reviewed journals and the far more conservative estimates published by the Intergovernmental Panel on Climate Change. That steep a rise in sea level would put significant parts of many California cities underwater in just two or three decades.

California is, theoretically, preparing for the effects of sea level rise, but not at a pace that satisfies sea level specialists. The state's planning relies on sea level rise projections that fall well below the three meters by 2060 Davidson suggests as a possibility. The California Coastal Commission, for instance, uses a 2012 summary from the National Research Council that suggests most of California will see sea level rises of between 18 inches and five and a half feet by the end of the century. As the Orange County Register's Aaron Orlowski reports this week, some affluent coastal communities are fighting efforts to prepare for even that much smaller amount of sea level rise.  

Why the discrepancy between the recent data reported anecdotally by Davidson and the formal pronouncements of the National Research Council and of the IPCC, which in 2013 was forecasting half a meter of rise by 2100? According to Insurance Journal reporter Don Jergler, Davidson told attendees in San Diego that the difference was due to the methodical nature of scientific study and peer review. 

"By the time we get out the [IPCC] report, it’s actually synthesizing data from about a decade ago,” said Davidson.

That's not all downside: the longer process also helps scientists avoid making rash judgments based on seemingly alarming data that turns out not to be as bad as it appears at first glance. It may be that the "OMG" data NOAA is getting from Antarctica actually results in less, and slower, sea level rise.

"The latest field data out of West Antarctic is kind of an OMG thing.”
Margaret Davidson, NOAA

That's worth hoping for, because three meters of sea level rise by 2050 or 2060 would be catastrophic for many parts of the world, including California. And 2050 isn't that far away. Sober forecasts of a meter or less of sea level rise by the end of this century are alarming in the abstract, but few people reading this in 2016 will be around to witness it. But mid-century? That's close. Children born this year will be in their early 40s in 2060. 

What would three meters of sea level rise look like in California? Southern California won't be as hard-hit as many places around the world, where millions of people live within a few feet of sea level in cities with no barriers between their residents and the surf. Southern California's coastal bluffs will protect much of the region's valuable real estate from direct inundation by three-meter-higher seas.

Most, that is, but not all. San Diego west of Interstate 5 is at risk, with low-lying neighborhoods like Barrio Logan and Mission Bay well within the inundation zone. Northward, anywhere there's a coastal estuary or creek we can count on the ocean growing new fingers to extend inland, with seawater flooding what had been irreplaceable freshwater marshes. South Bay shoreline communities from Huntington Beach to Terminal Island will be at risk of flooding: in some places land subject to inundation stretches halfway from the ocean to the 405. Venice and Santa Monica will lose their beaches. About half the Naval Air Station at Point Mugu will be at risk of flooding. So will about a third of downtown Carpinteria and the Santa Barbara airport.

That's some expensive real estate potentially going underwater in your children's early adulthood, but north of Big Sur is where the real changes to the map will be taking place. We can say goodbye to Monterey's Fisherman's Wharf neighborhood, for starters. The mouth of the fertile Salinas Valley will become a bay, as will the Pajaro River floodplain as far inland as Watsonville.

The Bay Area will be almost completely changed. Hilly San Francisco will be spared the worst of the damage, though it will lose UCSF's fancy new campus in the southeast part of town at Mission Bay. Downtown San Rafael will be underwater. The Bay will reach to Petaluma, Napa, and Fairfield — three cities well inland of the current Bay shore. The flats in Richmond and North Richmond, now populated by some of the Bay Area's least-affluent communities, will be underwater. Point Richmond will become an island a mile offshore. Oakland will lose its port, its airport, and many square miles of its most affordable housing in West Oakland and near the Coliseum. Between Hayward and Union City, a broad arm of the Bay will reach nearly to the base of the hills. Along the Peninsula, essentially everything east of Route 101 will be gone. So will downtown Milpitas.

And the most spectacular damage will be east of the Bay, in the Delta, as we mentioned in our recent piece on sea level rise and the Peripheral Tunnels. In that piece, we discussed the damage wrought by two meters of sea level rise. Three meters would be far worse. We could expect open water from West Sacramento — which would be lost without public works intervention — to Tracy, 60 miles south. Downtown Stockton would be gone. So would many miles of Interstate 5, which would skirt the east shore of the Sacramento Sea.

Interstate 80 flooding in the Delta, 2005 | Photo: Patrick Berry, some rights reserved

If the data from West Antarctica is as dire as NOAA's Davidson suggests, then California is faced with a staggeringly difficult series of choices. Building enough earthworks and levees and dikes to protect every single square mile of developed land under the three-meter mark by 2050 seems an impossible task: even if it were technically feasible, the cost would be astronomical.

And there are a few things to keep in mind. The potentially inundated areas listed here were mapped by  assuming the ocean was simply three meters higher. This method, referred to in sea level rise jargon as the "bathtub model," doesn't account for things like storm surges, seasonal floods as swollen rivers meet raised estuaries, or local variations in sea level due to phenomena such as El Niño. It also doesn't reflect the fact that once the Pacific reaches the three-meter mark, it'll keep rising from there.

There's also this: to get three meters of sea level rise by 2050 or 2060 we obviously have to reach one and two meters of rise sometime before that. Which means that — if Davidson's suggestions bear out — we're going to have our hands full in the lowest-lying areas, like the Sacramento Delta, very soon.

If Davidson's suggestions bear out, in fact, we will relatively soon be engaged in a public conversation about which parts of coastal Calfornia we abandon to the Pacific and which we harden with levees and breakwalls. If California's history is any indication, we're going to have to fight hard to keep real estate values from being the main factor determining what gets saved and what gets submerged. 

Or we could stop dumping greenhouse gases into the atmosphere, and minimize the damage to our coastlines. Just a thought.

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