This year’s atmospheric impact goes well beyond storms
Southern California may have braced for rains that never came, but this year’s massive El Niño made its mark nonetheless. While a high-pressure ridge sent much of the expected downpours north, profound effects of the phenomenon
gave scientists at Scripps Institution of Oceanography at UC San Diego much to interpret on several fronts:
Ocean temperature stratification
A classic El Niño condition involves sharp temperature contrasts between the ocean surface and bands of deeper water that cut off the supply of nutrients. Phytoplankton at the surface diminish substantially in a change that reverberates through the ocean food web.
Scripps biological oceanographer Mark Ohman led a cruise to collect data that could help infer if changes in marine life will occur in El Niño years. “We expect to see less total biomass, less living stuff,” says Ohman. “El Niños have changed traditional predator-prey relationships in both directions.”
Odd migration patterns
One of the most obvious signs of El Niño this year was the continued appearance of fish and other marine creatures in places where they don’t normally live. “Subtropical species such as Pacific bluefin tuna, opah, marlin and wahoo were observed well north of their usual ranges,” said Cisco Werner, director of NOAA’s Southwest Fisheries Science Center. “These observations can give us a glimpse into how our future ecosystems will look under more sustained warming conditions.”
Shifting sands
It’s common for energized waves of winter ocean to erode coastline sand from beaches, but while five or six feet is average, this year saw more than 10 feet of vertical erosion along the coast.
All that sand goes somewhere else, however. Several Southern California estuaries—and even the Tijuana River—were cut off from the ocean by displaced sand and cobblestones. “There’s a public perception that El Niño never came, but it certainly did from an ocean perspective,” said Scripps coastal oceanographer Sarah Giddings, who waded through several estuaries to measure how El Niño changed their internal workings.
Sea level surge
While this year’s El Niño brought less overall rainfall, it did bring very short, intense rains at abnormal times of the year. “These rains led to severe flash floods in several cities across the region, exemplifying how these climatic shifts can impact our businesses and communities,” says Laura Engeman, manager of the San Diego Regional Climate Collaborative, an information-sharing network of local cities, universities and other entities. “It is important that we plan now to make us more resilient to the impacts of these climatic extremes.”
Imperial Beach, for example, has begun assessing the vulnerability of its coastline to sea-level rise. “Imperial Beach experienced the most severe coastal flooding in more than 20 years this year on our beachfront and bayfront,” says the city’s mayor, Serge Dedina, Marshall ’87. “That experience—which we worked with our residents to prepare for—has only reinforced our decision to embark on our comprehensive sea-level rise and coastal flooding adaptation planning process. This year was a sign of things to come.”