Melting ice sheets in Antarctica will wallop California with greater sea-level rise than the world average, threatening the state's iconic beaches and important infrastructure, according to a report issued yesterday.

The latest science shows that the rate of ice loss from Greenland and Antarctica is increasing. That soon will become the primary contributor to global sea-level rise, overtaking ocean expansion from warming waters and the melting of mountain glaciers and ice caps, said the study, submitted to the California Ocean Protection Council.

That ice loss causes higher sea-level rise in California, it said, due to how the Earth rotates and gravitational pull on the waters. If the ice melt is from West Antarctica, impacts extend further.

“For California, there is no worse place for land ice to be lost than from the West Antarctic Ice Sheet,” the study said. “For every foot of global sea-level rise caused by the loss of ice on West Antarctica, sea-level will rise approximately 1.25 feet along the California coast.”

Melting in Antarctica puts the California coast essentially “in the bull's-eye” of the magnified sea-level rise, said Dan Cayan, director of the Climate Research Division at the Scripps Institution of Oceanography in San Diego.

Cayan was one of seven authors of the report, produced by a working group of the California Ocean Protection Council Science Advisory Team. The council asked for an update on a similar report done in 2010 and updated in 2013. Another one was needed because of newer science and projections on sea-level rise, said John Laird, council chairman and California Natural Resources Agency secretary.

The council will hold workshops this spring and summer on the research, take comments and issue a draft proposal for how to turn it into policy this fall. That could be approved by January.

Sea-level rise already is affecting coastal California, the study said. It's causing more extensive coastal flooding during storms, periodic tidal flooding and increased coastal erosion. Over the short term, the state faces higher sea levels from phenomena like El Niño, during which the central Pacific Ocean warms. El Niño also can trigger stronger storms, which, when combined with sea-level rise, can trigger mudslides, floods and avalanches in the mountains.

Rising seas will worsen, although exact amounts depend on a number of factors, including whether countries successfully curb greenhouse gas emissions and limit temperature rise, it said.

Until 2050, there are minor differences in sea-level rise projections based on greenhouse gas pollution scenarios. They diverge significantly past midcentury, the study said. It gave possible sea-level rise amounts looking at three California locations where there are tide gauges: Crescent City in northern California, the Golden Gate Bridge in San Francisco and La Jolla in San Diego.

By the turn of the century in San Francisco under the lowest estimate, the sea would rise 1 foot. It could climb as much as 6.9 feet. In La Jolla, the ocean would lift 1.1 feet under the lowest estimate or as much as 7.1 feet.

Crescent City faces a range of 1.2 inches under the lowest estimate to as much as 5.9 feet.

10-foot rise possible

The report also said those estimates might fall far below what actually transpires, however. They might underestimate “the likelihood of extreme sea-level rise,” particularly under high greenhouse gas emissions scenarios. It describes one that could bring a 10-foot rise to California by the turn of the century.

“The probability of this scenario is currently unknown, but its consideration is important, particularly for high-stakes, long-term decisions,” the report said.

Some speakers at the meeting, including a California Coastal Commission representative, expressed concern that the low estimates in the report could mislead some people.

“The probability information as currently presented could have the unintended consequence of reducing or reversing the progress that is being made in planning for sea-level rise,” said Madeline Cavalieri, coastal planner at the California Coastal Commission. The low scenarios don't account for the latest science on ice sheet loss, she said.

Some people “may use the tables to select sea-level rise projections that are lower than what is recommended by the current state guidance,” she said.

Cavalieri praised the report for including the extreme scenario with the possible 10-feet scenario, saying it is important for planning to protect critical infrastructure. Coastal Commission staff members currently are working on adaptation blueprints with more than 30 cities out of 76 local governments located in the sea-level rise zone, she said.

David Behar, climate program director at the San Francisco Public Utilities Commission, cautioned that the state needs to be “more transparent and clear about where 10-foot number comes from.”

“That's the biggest number that I've seen in any of the reports, including in the NOAA report ... so we need to understand where that number came from and help people understand how to use it, ” he said. His agency likely will increase rates to fund adaptation, he said, so clarity is essential.

Gavin Newsom, California lieutenant governor and chairman of the State Lands Commission, at the meeting expressed frustration with how to deal with the study results.

“This is all interesting, but what the hell do we do about it,” outside of the state maintaining its actions to cut greenhouse gas emissions and limit climate change, Newsom said.

There are planning issues the state needs to think about, not just on the coast but in the Sacramento-San Joaquin River Delta, the system that provides a large share of the state's drinking water, Cayan said. The delta has leveed islands. If those are overtopped, he said, the circulation and the salinity gradient would change.

California also is considering a massive project installing tunnels beneath the delta to carry water to Southern California instead of the current pumping system. The state might need to carefully study the design and the height of the pipes that would draw the water, Cayan said, to make sure they are high enough.

“California really has to be a leader because this is such an important problem, both from direct impacts but geopolitically, with a lot of populations that are in harm's way,” Cayan said.

There's also the issue of social justice, he said, as “some of the folks that are least able to build a sea wall, or whatever it is, are maybe more exposed.”

Reprinted from Climatewire with permission from E&E News. E&E provides daily coverage of essential energy and environmental news at www.eenews.net.