기후 변화에 따른 엘니뇨 특성

Abstract

El Nin˜o events, characterized by anomalous warming in the easternequatorial Pacific Ocean, have global climatic teleconnectionsand are the most dominant feature of cyclic climate variability onsubdecadal timescales. Understanding changes in the frequency orcharacteristics of El Nin˜o events in a changing climate is thereforeof broad scientific and socioeconomic interest. Recent studies1–5show that the canonical El Nin˜o has become less frequent and thata different kind of El Nin˜o has become more common during thelate twentieth century, in which warm sea surface temperatures(SSTs) in the central Pacific are flanked on the east and west bycooler SSTs. This type of El Nin˜o, termed the central Pacific El Nin˜o(CP-El Nin˜o; also termed the dateline El Nin˜o2, El Nin˜o Modoki3 orwarm pool El Nin˜o5), differs from the canonical eastern Pacific ElNin˜o (EP-El Nin˜o) in both the location of maximumSST anomaliesand tropical–midlatitude teleconnections. Here we show changesin the ratio of CP-El Nin˜o to EP-El Nin˜o under projected globalwarming scenarios from the Coupled Model IntercomparisonProject phase 3 multi-model data set6. Using calculations basedon historical El Nin˜o indices, we find that projections of anthropogenicclimate change are associated with an increased frequencyof the CP-El Nin˜o compared to the EP-El Nin˜o. When restrictedto the six climate models with the best representation of thetwentieth-century ratio of CP-El Nin˜o to EP-El Nin˜o, the occurrenceratio of CP-El Nin˜o/EP-El Nin˜o is projected to increase asmuch as five times under global warming. The change is related to aflattening of the thermocline in the equatorial Pacific.