Characteristics and trends of the Campbell Plateau Meander in the Southern Ocean

The Southern Ocean is a crucial component of the global climate system and has absorbed a large proportion of anthropogenic heat and carbon emitted since the pre-industrial era. The Antarctic Circumpolar Current is composed of fronts, jets, and meanders. Meanders are \meandering\" currents often overlapping the location of fronts and close to topographic features and are sites of locally enhanced vertical transport and mixing. Although meanders are key sites of interactions between the surface and deeper waters their response to climate change is largely unexplored. In this study we investigate the Campbell Plateau meander south of New Zealand using satellite altimetry data over the 1993-2020 period. We apply a \"local gradient maxima\" method to absolute dynamical topography data from satellite altimetry to identify the meander's location. The meander's width and geostrophic current speed are also derived. The linear trends of the meander's meridional displacement width as well as speed are estimated and their statistical significance is tested. From 1993 to 2020 the meander's location has been largely fixed except for downstream from the Plateau shifting northwards by 0.4° latitude per decade. The meander has become flatter at the western edge of the Plateau but steeper at its eastern edge. Furthermore the meander has overall been widening by 2 km per decade and accelerating by 0.01 m \\(s\\)\\(^ {-1}\\) per decade particularly downstream from the Plateau. These findings are similar to other results from ongoing work on the Agulhas-Kerguelen standing meander located in the Indian sector of the Southern Ocean. While we cannot attribute these trends to one particular forcing we discuss several hypotheses. The observed widening and accelerating of the meander may hinder the cross-frontal transport of heat and other tracers but could enhance the local vertical tracer transport. Whether these trends are applicable to the whole Southern Ocean meanders remains to be verified."