Science

Less Sea Level Rise for Left Coast

by | Mar 21, 2022

Western Canada’s Mackenzie River plays a major role in Arctic climate as warmer fresh water mixes with cold seawater. Photo: NASA/USGS 2017.

Estuaries invite sea level rise inland. Here Western Canada’s Mackenzie River plays a major role in Arctic climate as warmer fresh water mixes with cold seawater. Photo: NASA/USGS

Scientists are now more confident we should plan for up to a foot of sea-level rise on the Pacific Coast by 2050 than they were the last time they did the math. That’s because this time when they compared the projections from computer models with projections from actual tide gauges in coastal waters and satellite altimetry (bouncing radar off the ocean surface to measure height changes), they got the same results. 

“What’s new is that models and observation-based projections corroborate each other,” says US Geological Survey coastal hazard scientist Patrick Barnard. “We’re getting better at using multiple lines of evidence to support projections.”

The sea-level-rise science, released by an interagency federal task force (NOAA, USGS, FEMA, et al) this February, builds on scenarios in the recent Intergovernmental Panel on Climate Change’s Sixth Assessment. For the US coastline in general, the report projects an average rise of 10-12 inches within the next 30 years. The East Coast could go higher (up to 14 inches), and the Gulf Coast higher still (up to 18 inches), while the West Coast could be lower (4-8 inches). Scientists were also confident enough about the new, ground-truthed math that they threw out a more extreme earlier projection. 

 “We’re pretty confident now about what we’ll see by 2050, but after that depends on emissions scenarios and the speed of ice sheet response,” says Barnard, a co-chair of the task force. “The latest science out of Antarctica is that despite observed ice sheet instability, and even if there is catastrophic loss, sea level will likely take longer to respond than what was originally thought possible. 

While the near-future news is better for the West Coast than for other coasts, the San Francisco Bay Area will still suffer because so much of its infrastructure is built at low elevations right along the shoreline, often on sinking Bay fill. USGS projects 150,000 people and $50 billion worth of property across California are at risk of coastal flooding given the new 2050 projection. The Bay Area accounts for two-thirds of statewide impacts, says Barnard.

The East and Gulf coasts will be worse off mainly because they are sinking. “They have some of the highest rates of land subsidence in the country,” says Barnard, pointing out the Gulf Coast’s long history of oil and gas drilling and groundwater removal, and both coasts’ big muddy deltas and estuaries “that settle and sink over time.” Warmer water off these coasts also adds more volume to the ocean in these areas that cooler currents off the West Coast prevent. 

Another difference in the three coasts is relief. The East and Gulf coasts are relatively flat, with few coastal mountains to stop the advance of storm surges and sea-level rise, and many wide-mouthed estuaries to invite these waters in. California’s coastal mountains, rocky shores, and narrow-mouthed estuaries (like the Golden Gate) reduce some impacts of sea-level rise.

Other sorts of flooding aren’t so stymied by California’s steep shores. The November 2021 atmospheric river over the Pacific sent torrents down hillsides to pool at the base of Marin County watersheds, for example, just where the Bay is also creeping inland, pushing groundwater higher, too.

Other Recent Posts

The Lost Birds, A Review

The loss of avian diversity inspired The Lost Birds, the latest work by composer Christopher Tin, who is best known for scoring video games and movies. Released in September 2022, The Lost Birds is a tribute to extinct animals.

New Flood Protection Standard for the Peninsula

In San Mateo County, new planning guidance may help cities account for rising seas when approving new developments. OneShoreline’s proposals are stricter than current requirements from federal, state, and local agencies, but those are also evolving. “The intent is to go where we already see regulators are going,” says Makena Wong, a project manager.

Shores that Can Shapeshift AND Stay Put?

The region is obsessing over beach-building. Whether it’s a degraded salt marsh in downtown San Rafael or a sliver of wetlands near the old San Francisco shipyards, local practitioners are adding beaches as nature-based buffers against waves and rising seas to adaptation projects around the Bay.

Humanity on the Fence

A new public art installation, called Fencelines, redefines the only barrier separating Richmond’s residential neighborhoods from the Chevron oil refinery: a wire fence.

Growing a Rainbow in the Urban Dirt

Debbie Harris directs Urban Adamah, a Jewish urban farm in Northwest Berkeley. She is a farmer by trade but her role at Urban Adamah requires her to be “a horticulturalist, a plumber, a therapist, a teacher, an organizer.”

Food Forests Green Solano

This spring, Sustainable Solano hosted open gardens that they helped plan and plant, offering visitors a chance to discover these food forests: a garden layered like a natural forest that includes fruit-bearing trees and edible plants.

Hollywood a Black Hole on Climate Change?

A USC study on “climate silence” reported that only 0.6% of all scripted film and television released between 2016 and 2020 mention the term “climate change” and only 2.8% of all scripts included any climate-related terms.

Projected coastal flooding frequencies in the US by 2050. Source: NOAA/USGS.

Projected coastal flooding frequencies in the US by 2050. Source: NOAA/USGS.

“Flood frequency is also going to increase exponentially with sea-level rise,” says Barnard. According to the new science, by 2050 damaging flooding will occur more than ten times more often than it does today, or about four times a year as compared to once every three years at present. Though the science also projects flooding will be a bit less frequent in California than on the other coasts, it’s still a worry. “Everything is going to be riding on top of an extra foot of sea level, which could tip the scales in many low-lying coastal communities.”

Everything is also riding on when and how those ice sheets melt, and where in our oceans the melt water ends up. Barnard says just because one coast may be closer to melt sources than another does not mean it will experience higher sea levels — but sorting that all out requires much more complex science.  

We can now plan with more certainty for one foot of sea-level rise by 2050. But beyond that is the stuff of politics and the profit motive. Even the best science can’t account for the uncertainties of human meltdown.

About The Author

Ariel Rubissow Okamoto

is KneeDeep’s managing editor. She is a Bay Area environmental writer and editor and co-author of a Natural History of San Francisco Bay (UC Press 2011). For the last decade, she’s been reporting on innovations in climate adaptation on the bayshore (Bay Nature). She is also an occasional essayist for the San Francisco Chronicle. In other lives, she has been a vintner, soccer mom, and waitress. She lives in San Francisco close to the Bay with her architect husband Paul Okamoto.