El Nino is one side of the climatic coin called the El Nino-Southern Oscillation. It’s the heads toDuring El Nino, a swath of ocean stretching about 10,000km westward off the coast of Ecuador warms for months on end, typically by about 1 degree Celsius to 2 degrees Celsius. A few degrees may not seem like much, but in that part of the world, it’s more than enough to completely reorganise wind, rainfall and temperature patterns all over the planet.
Specifically, El Nino tends to trigger intense and widespread periods of extreme ocean warming known as marine heat waves. For example, some fish increase their metabolism in warm waters by so much that they burn energy faster than they can eat, and they can die. Pacific cod declined by 70 per cent in the Gulf of Alaska in response to a marine heat wave.Other impacts include bleached corals, widespread harmful algal blooms, decimated seaweeds and increased marine mammal strandings. All told, billions of US dollars are lost to marine heat waves each year.
Peruvian fishers have for centuries weathered periods of extreme ocean warming that drive fish away. It wasn’t until the 1920s that scientists realised that these South American marine heat waves were related to the Pacificwide El Nino-Southern Oscillation.
... and the fish?