Thermohaline Properties and Trends in the Antarctic and Subantarctic Regions of the Pacific Ocean using 20 years of Argo float data

The Antarctic and Subantarctic regions of the oceans, situated mainly in the Southern Ocean, play a crucial role in connecting all oceans through the Antarctic Circumpolar Current (ACC). It is essential to better understand the processes that occur in these regions, such as water mass formation, deep convection, and hence their contribution to the Meridional Overturning Circulation (MOC). Particularly noteworthy areas are those with abrupt bathymetric changes, such as the Campbell Plateau in southwestern New Zealand.  In the present study, Argo floats data from 2003 to 2024 are used to identify the main water masses  along the sectors from the eastern and western edges of the Campbell Plateau to the Antarctic continental shelf. These sectors, located between subtropical and subantarctic fronts, are characterized by the formation of Sub-Antarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW), which contribute to shaping the broader oceanic circulation patterns. Recent results reveal the presence of eight distinct water masses in the study region and emphasize their peculiar seasonal variability. Also, a decadal analysis identifies  colder waters in the period 2003-2013 compared to 2014-2024, while significant changes in the trends of salinity and temperatures are observed in the different sectors. Preliminary results of this study highlight a unique 'dual mode' in temperature dynamics, where rising temperatures in one sector are accompanied by declining temperatures in the other. Similar patterns were also found in the salinity results. Finally, the use of Argo float data provides an unprecedented level of detail in examining the spatial and temporal resolution of an area located between these two different sectors of the ACC, whose changes most likely influence the global and Southern Ocean circulation patterns, with consequent implications on climate.