Comparative Analysis of Jet Detection Methods on the Basis of Satellite Altimetry Data by Example of the Antarctic Circumpolar Current Sector to the South of Africa

Abstract—

For the period of satellite altimetry observation 1993–2018, a comparison was made of estimates of the linear meridional shifts of the jet structure and variations in current intensity in the sector of the Antarctic Circumpolar Current (ACC) south of Africa (10° E–25° W), obtained on the basis of the parameters derived from the module of the absolute dynamic topography (ADT) gradient \(\left| {\nabla \zeta } \right|\): directly \(\left| {\nabla \zeta } \right|\), module of the velocity of geostrophic current |u| on the ocean surface, half of square of the ADT gradient \(\frac{1}{2}{{\left| {\nabla \zeta } \right|}^{2}}\), and specific kinetic energy \(\frac{1}{2}{{u}^{2}}\). The analysis was carried out by a method developed earlier and refined in this paper using linear regression analysis. It is shown that qualitatively the characters of the meridional shifts (displacement of the curves of these parameters averaged over latitude and for each year) in latitude and the corresponding current intensity variations (i.e., variations in the parameters themselves) over 26-year observations, when calculated through each of the four parameters, turned out to be similar. The same similarity was obtained from the calculations with respect to the ADT scale. Meanwhile, the quantitative differences between calculations for different pairs of parameters can be significant even in the \(\left| u \right|\) and \(\left| {\nabla \zeta } \right|\) pair. In quantitative terms, the absolute values of shifts of the jet structure and variations in the intensity of currents in the ACC band in the studied sector of the Southern Ocean generally increase from those linearly dependent on the ADT gradient module to quadratically dependent ones.