Remote influences on freshwater flux variability in the Atlantic warm pool region

Abstract

The understanding of freshwater flux variability is both scientifically and socially important. Local freshwater flux response to a large Atlantic warm pool (AWP) is excessive freshwater or negative Evaporation minus Precipitation (EmP) anomalies, whereas the response is deficient to a small AWP. However, the EmP anomalies in the AWP region are also influenced by the SST anomalies in the tropical eastern Pacific and in the tropical South Atlantic. These remote influences operate through the inter‐basin mode represented by the SST gradient between the tropical North Atlantic and eastern Pacific and the Atlantic meridional mode (AMM) defined as the SST gradient between the tropical North and South Atlantic. When either of these two modes is in the negative phase, the EmP and sea surface salinity anomalies in the AWP region can be positive although the AWP is large. This indicates that the remote influences of the inter‐basin mode and/or the AMM can overwhelm the local effect and induce an opposite freshwater response. Additionally, although ENSO and the AMM sometimes coincide with AWP variability, an El Niño in the preceding winter or a positive AMM in the spring does not necessarily follow a large AWP in the summer.