Pacific–Atlantic Interactions Heat Up: Evidence from El Niño and Mid-Latitude Blobs

In this talk, evidence will be presented to demonstrate that interactions between the Pacific and Atlantic Oceans have increased in the past two decades resulting in a greater number of synchronized occurrences of marine heatwave and cold spell events (aka. warm and cold blobs, respectively) in North Pacific and Atlantic and also more frequent occurrences of the Central Pacific (CP) El Nino.

Most previous studies have emphasized processes within the tropical Pacific for the generation of El Niño. We will show that after a change in the phase (from negative to positive) of the Atlantic Multi-decadal Oscillation (AMO) in the early 1990s, the Atlantic Ocean has been more capable of influencing El Niño dynamics. As a result of the stronger Pacific-Atlantic interactions, El Niño has changed from being predominantly of the Eastern Pacific (EP) type to being predominantly of the Central Pacific (CP) type and has become more biennial. The sequence of the physical processes that involved in this interaction will be presented.

We will also show evidence that during this same time period unusually prolonged North Pacific heatwaves (i.e., Pacific warm blobs) have a tendency to occur together with prolonged North Atlantic cold spells (i.e., Atlantic cold blobs). These synchronized extreme events are accompanied by a unique circulation pattern in the atmosphere, which exhibits a unique cross-basin structure. We will discuss how this pattern can serve as an atmospheric conducting pattern to induce co-variability in the North Pacific-Atlantic Oceans and why it has occurred more often recently.