An Argo Float Study of Temperature and Salinity in the Subpolar region of the Cambpell Plateau

Abstract

The Subantarctic region of New Zealand is marked by a unique and complex bathymetry that includes an ocean ridge and a substantial submarine plateau known as the Campbell Plateau. This plateau is located near the Pacific sector of the Southern Ocean, and plays a vital role in the export of heat, salt, and nutrients into the lower thermocline, primarily through the formation of mode waters. In the present study, Argo floats data from 2003 to 2023 are used to identify the main water masses along the eastern margin of the Campbell Plateau. This region, located at the boundary between subtropical and subantarctic fronts, is characterized by the formation of Sub-Antarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW), which make an important contribution to the broader oceanic circulation patterns. First results reveal the presence of eight distinct water masses in the study region and emphasize their peculiar seasonal variability. A decadal analysis describes colder waters in the period 2003-2013 compared to 2014-2023, while significant changes in salinity are observed in 2017-2018. Water mass identification, depicted through Temperature-Salinity plots, is consistent with existing literature, but can also provide new insights on the interaction between subantarctic and subtropical waters. This research contributes to describe the ocean dynamic of Subantarctic New Zealand. The use of Argo float data provides an unprecedented level of detail in examining the spatial and temporal resolution of an area located between two different current systems, whose changes potentially influence the global and Southern Ocean circulation patterns, with consequent implication on the climate.