Posted on Categories Discover Magazine
If the mom and pup Galápagos sea lions in the photo above seem content, it could be that we’re simply projecting human emotions onto them. Or it may just be that that their bellies are full with fish. In fact, barring close encounters with rapacious sharks, they’ve probably had it pretty good lately — thanks to La Niña. Now in its third year, the climate phenomenon typically brings a bounty of food for marine animals foraging in the waters of the Galápagos Islands. But now, according to the latest forecast, La Niña is poised to leave the stage. And there are tentative signs that its alter-ego, El Niño, is warming up for an appearance next fall — literally so, since El Niño brings abnormally warm waters to that part of the equatorial Pacific Ocean. Should that happen, Galápagos marine life won’t be the only ones to suffer. La Niña and El Niño are two sides of the climate coin known as the El Niño-Southern Oscillation, or ENSO. Around the Galápagos, La Niña benefits marine animals, whereas El Niño can send populations plummeting. Beyond that, both phenomena affect both wildlife and millions of people living thousands of miles away. In the case of El Niño, its warming of ocean waters sends waves of disruption rippling through the ocean and atmosphere, thereby promoting extreme weather events — from flooding and landslides to severe drought. Is that outcome looming? Bye Bye La Niña “La Niña — the cool phase of the El Niño-Southern Oscillation climate pattern — weakened over the past month, and forecasters expect a transition to neutral conditions in the next couple of months,” writes Emily Becker of the University of Miami’s Cooperative Institute for Marine & Atmospheric Studies. Looking further ahead, there’s a 60 percent of El Niño grabbing the spotlight during the fall. But right now, that forecast is highly uncertain. (For the reason, keep reading…) If El Niño does show up, many Galapagos sea lions — an endangered species — and other marine animals in the region, will perish. In fact, during the strong El Niño of 2015, the sea lion population declined by nearly one quarter. El Niño has this impact because the warm waters it brings to the region tend to be lacking in nutrients, reducing productivity of the marine ecosystem. For Galápagos sea lions, this means fewer fish to eat, and fewer pups surviving. Over the longer term, global warming could make El Niño years even more challenging for the species, and others as well, including fur seals and Galápagos penguins. (You can check out the details in this story.) The impact on marine life extends beyond the Galápagos. In neutral years, when neither El Niño nor La Niña are present, cold ocean water upwelling from the deep along the coast of the Americas brings nutrients to the surface. This sustains plankton at the bottom of the food chain — an effect that’s intensified during a La Niña. But during an El Niño, the upwelling is suppressed, causing fish to perish or migrate. Animals that eat the fish, including birds and sea lions, tend to suffer. As do fishermen who ply the waters off Ecuador and Peru. Impacts on Us Through the unusual heating of ocean waters along the equator in the Pacific, El Niño also affects the weather on every continent — even including Antarctica. As Kevin Trenberth, a Distinguished Scholar at the National Center of Atmospheric Research, explains it: “Somewhat like a rock sitting in a stream of water, this unusual heating sets up teleconnections: continental-scale waves in the atmosphere that extend into the midlatitudes in winter.” These waves ultimately alter the path of the jet streams that encircle both hemispheres of the globe. In the Northern Hemisphere, the mid-latitude jet stream racing west across the Pacific is shifted south of its neutral position during an El Niño. The result: the northern United States and Canada tend to be drier and warmer than usual. By contrast, the U.S. Gulf Coast and Southeast tend to experience heavy rains and increased flooding. California and the southwestern United States can also be wetter than usual during an El Niño episode — which would be more good news for the drought-stricken region following the recent heavy precipitation there. But this impact tends to occur during stronger episodes. And we simply don’t know yet whether an El Niño is ready to take center stage, let alone whether it will give a strong performance. That’s because at this time of year, and moving into the spring, computer models have a hard time making accurate forecasts of what’s coming in the fall. (Scientists call this the “spring predictability barrier.”) After spring, the models should get increasingly accurate. In the meantime, forecasters are now quite confident that La Niña is ready to take her bows, with an 85 percent chance that the February through April period will wind up with neutral conditions. Beyond that, we’ll just have to wait for more reliable forecasts. Either way, mom and pup Galápagos sea lions would be well advised to partake of La Niña’s bounty of fish while they can.