Connections Between Surface and Subsurface Temperature Anomalies

Temperature anomalies, such as marine heatwaves and cold spells, are often studied as sea‐surface phenomena. Substantial temperature anomalies are also present in the subsurface, but subsurface temperature data are sparser. Here we use 1° × 1° × 7 day resolution ocean temperature maps from 1993 to 2023 to explore the dominant relation of surface temperature anomalies to those below the surface, finding three different temporal relationships between them in different regions. In parts of the subpolar Northeast Pacific as well as small areas in the tropical North Pacific and tropical South Pacific, we find a dominant “top‐down” relationship, where subsurface temperature anomalies lag surface expressions, lingering for months to years afterward. In the central‐eastern equatorial Pacific, “bottom‐up” subsurface temperature anomalies tend to be initiated before those at the surface. In western boundary currents, their extensions, and other areas with strong currents or eddies including the Antarctic Circumpolar Current, “all‐at‐once” surface and subsurface temperature anomalies are often simultaneous, as eddies and current meanders often perturb temperatures throughout the upper ocean, including at the surface. This study provides a global overview of the dominant patterns of connectivity between surface and subsurface temperature anomalies, with patterns of vertical propagation that match larger oceanographic features. As such, this type of analysis holds promise for future understanding of the mechanisms of formation of temperature extreme events both at the surface and at depth.