Annual amphidromic columns of sea temperature in global oceans from Argo data

Abstract

Nearly a decade ago, it was recognized that “amphidrome” is not a tide-only feature. Although more than a dozen annual amphidromes have been reported for several oceanic/atmospheric variables, little has been done so far to identify nontidal amphidromes under the sea surface. In this study, analysis of annual phase properties of sea temperature at different depths has been conducted using Argo data. As a result, four annual amphidromic columns of sea temperature (AACST) with different thicknesses have been identified across the tropical oceans. The concept of “amphidromic column” is defined for the first time as the water column where an amphidromic point extends vertically for a given depth in the ocean. Given the fact that it is coupled with the lower limit of the oceanic mixed layer and provides a direct measure of the solar penetration, the determination of AACST has many potential implications ranging from a more precise monitoring of the interannual to multidecadal temperature changes under global warming, to a better understanding of the thermal-dynamical, biological, and fishery processes in the tropical oceans.