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Delta Flows: Sea Level Rise and The Delta

I was minding my own business, checking Twitter Tuesday morning, December 10, when I saw this article from the Washington Post:

“Septupled”—I had to think about that for a moment. Greenland’s rate of ice melt increased by a factor of seven times, reported the Post. Since 1992, Greenland’s ice sheet lost just 33 billion tons to neighboring oceans, compared with 254 billion tons now—an acceleration of 7.6 times. The 89 scientists authoring the Greenland report stated: “The Greenland Ice Sheet holds enough water to raise mean global sea level by 7.4 [meters, or about 32 feet on average].” The current melting rate is enough to raise global sea levels vertically about 1 centimeter (about three-eighths of an inch), they found. 

Greenland study co-author Andrew Shepherd of the University of Leeds told the Post, “Around the planet, just 1 centimeter of sea-level rise brings another 6 million people into seasonal, annual floods.”

A centimeter doesn’t sound like much. Why worry? But then you have to remember that this is a vertical estimate in a world where the seas ebb and flow horizontally, as tides influenced by our Moon. 

Okay, I thought. But what does that look like?

I turned to glaciologist Eric Steig, whom I follow on Twitter. He also had tweeted out the actual scientific study from Nature, and we conversed via Twitter.

“Sea level” measures all the sea levels that go with our tides—there’s an average tide, as well as high and low tide levels. So I asked Steig about tidal range—the degree to which sea levels’ vertical rise is boosted by the horizontal reality of more water in the ocean basin. “One cm [centimeter] vertically can be many meters horizontally,” he wrote, adding, “Also, this is just so far. Mass loss from Greenland ice is, and will continue, accelerating.”

Think of your bathtub for a moment. You have the spigot on—that’s Greenland melting and the tub is filling (and we’re not even talking about the west shelf of Antarctica’s ice sheet yet). Your kid is in there too, sloshing the water around, like the moon acting on our tides, at least sort of. The fuller the tub gets, the more water your kid moves by sloshing—vertically and horizontally. After you towel off your kid, you get the mop.

After I disclosed to Steig that I had in mind the California Delta and that the Delta is often severed in sea level rise analyses from the California coast, he replied, “Note that in many locations, subsidence dominates over sea level rise. So your local sea level rise may be much faster.” He said nothing direct about our Delta, but the implication is clear: Prepare

We expected early on that the Newsom Administration was going to lead aggressively on water and climate change. We wrote to them in our Climate Equity and Seismic Resilience report this summer that “new ice-sheet research needs to be factored into the climate change analysis produced for the Newsom Administration’s Water Resilience Portfolio.” (p. E-1) The administration’s much-delayed portfolio plan is supposed to be out later this month—though originally it was expected in October. 

The longer the portfolio plan is delayed, the worse we expect it will be. The more it will be about water and “business as usual” and not climate equity and equitably distributed social resilience. The more we hear about voluntary agreements, Sites Reservoir, a single-tunnel project, a permanent water service contract for Westlands Water District and other Central Valley Project contractors, rumors of a water bond in 2020, and proposed taxpayer funds for repairing the Friant-Kern Canal disabled by groundwater overdraft and land subsidence, the more likely it seems to us that this administration’s commitment to water resilience will look just one tunnel shy of Governor Jerry Brown’s. 

These proposals are the water industry’s grab to control the state’s future water supplies at the expense of environmental and climate justice for the Delta, the public trust, reasonable uses and methods of diversion, and reduced Delta reliance for the state’s future water needs. California will have dithered away another year not adapting to climate change and sea level rise our water system, our rivers, our Delta, and our “California water conservation way of life.”

Greenland’s melting accelerates, and so will sea level rise. Last summer, we urged the Newsom Administration to embark on Delta levee investments as a key part of California’s future water resilience. So much depends on this recommendation: public safety throughout the Delta, our region’s agricultural economy, our water quality here and for exports to other parts of California depend upon making and enacting such important priorities as the implications of sea level rise reach us. Our report reminded the Newsom Administration, that it’s not just sea level rise: it’s our response to the combined effects of climate change—effects that we can and must anticipate—of sea level rise, storm surge from the Bay, and river runoff from atmospheric rivers that hold the survival of the Delta. 

We hope they listened.