New data from ocean microbes in the Soledad basin off the coast of Baja, Calif., confirms a La Niña-like effect cooled surface waters 4,000 to 10,000 years ago.
Previous studies of one microbe species in sediment cores found cooler waters during this period of the Holocene, but scientists were not sure whether La Niña was at play, or more local effects like deeper waters welling to the surface were responsible.
Trade winds move warm waters from east to west over periodic cycles that occur over several years. La Niña – the cooling effect – brings cooler, drier weather to the United States. It is the opposite of warmer, wetter El Niño-induced seasons. In addition to these global effects, currents and local weather conditions also circulate deep, cold, nutrient-rich waters to the surface, an upwelling that replenishes nutrient-depleted surface waters.
Adding data from two more microbial species — one a summer-loving variety and another that lives in deeper waters — researchers now confirm the La Niña cooling effect. Hannah Grist, a graduate student at the University of Colorado, Boulder, presented the new results at a poster Thursday morning at the American Geophysical Union’s Fall Meeting in San Francisco.