It's easy to think of sea-level rise as a uniform force, occurring simultaneously and in equal measure along coastlines around the world. However, a pair of recent studies have illustrated just how complex and variable the phenomenon really is. Most relevant to us here in the Bay Area was a report released Friday by the National Research Council, a private nonprofit based in Washington, DC. It identified a particularly unexpected factor in sea-level rise: plate tectonics.
Turns out that the San Andreas Fault is causing the California coast from Cape Mendocino south to subside, exaggerating the impacts of sea-level rise. As a result, the organization anticipates that sea level in the Bay Area will rise by 3 feet 3 inches over the next century, a figure slightly higher than the forecasted global average. That's not good news for the region's many developed low-lying areas. San Francisco International Airport, for example, could flood if waters rise by as much as sixteen inches, which could happen in just a few decades.
Above Cape Mendocino and all the way up through Washington, however, shifting plates are producing the opposite effect: the land itself is lifting, mitigating the effects of sea-level rise. As a result, the National Research Council predicts that sea levels will rise along that broad swath of coastline by about two feet.
A second study, released on Sunday in the journal Nature Climate Change, showed that sea-level rise on the northern half of the US East Coast is occurring at a rate three to four times the global average, reported the Christian Science Monitor. In this case, the culprit is ocean currents. "When the Gulf Stream and its northern extension slow down, the slope of the seas changes to balance against the slowing current," the CSM writes. "That slope then pushes up sea levels in the Northeast. It is like a see-saw effect ...."
While plate tectonics and ocean thermodynamics may seem a bit arcane when it comes to the reality of rising sea levels caused by warming waters and melting polar ice caps wreaking havoc along coastlines in the Bay Area and around the world, there's no doubt they play a role in meting out the damage. Sea-level rise is not static; it's living and dynamic, making another recent piece of news all the more confounding: North Carolina legislators recently drafted a bill that would limit sea-level rise for planning purposes to a somewhat arbitrary figure based on past results rather than newer, higher projections that scientists consider much more accurate. A few days ago, however, it looks like they came to their senses.