Cerovecki, I., and Haumann, A. (2024)
Presented at:
Ocean Sciences Meeting 2024Subantarctic Mode Water (SAMW) subduction represents one of the main processes governing the transport of properties from the surface mixed layer, where this water mass is in contact with the atmosphere, into the ocean interior. Strong quasi-decadal variability of SAMW properties in recent decades thus represents significant perturbation to the upper ocean heat and freshwater content. We examine the mechanisms governing this variability, patterns of variability, and propagation pathways. Both the observations (gridded Argo product) and a state estimate (ECCO4v4) show that strong temperature and salinity anomalies enter the SAMW density range in 50-60 degree S latitude band, and are being advected northward into subtropics, and tropics (up to 10 degree S). Variations in the surface atmospheric forcing control the properties of the subducted SAMW as well as the longer-term variability of subsurface properties. Particularly strong is 2000-2012 temperature decrease within the SAMW density range in the southeast Pacific, partly driven by atmospheric tropical teleconnection from the post-2000 negative phase of the Interdecadal Pacific Oscillation. Around 2014-2015, when the Interdecadal Pacific Oscillation shifted to its positive phase, it was followed by SAMW temperature increase. We explore the implications of such strong temperature anomalies for the upper ocean heat budget of the tropical Pacific.
