Interannual and Seasonal Variation of Axis Position and Intensity of the Antarctic Circumpolar Current by Satellite Altimetry
Geophysical Center RAS,
3, Molodezhnaya Str.,
The Antarctic Circumpolar Current (ACC) develops to area of convergences and divergences of the Southern Ocean, which is confined of Subantarctic Front (SAF) and Polar Front (PF). Position of the SAF and PF were constructed from Multi-Cannel Sea Surface Temperature (MCSST) gradients based on satellite AVHRR data. According to the SAF and PF average annual position the ACC northern and southern borders was determined as 60 and 100 cm isolines in Rio and Hernandez (2003) combined mean dynamic topography (CMDT), which calculated by in situ measurements relative to 1500 dbar.
The ACC axis was defined as location of geostrophic surface speed maximum along meridian between stated isolines on the synoptic dynamic topography (SDT), which are constructed by superposition of sea level anomaly altimetry data with corresponding CDT. Value of surface speed on the ACC axis was determined as intensity of this current.
Along ACC axis seven local maximum of geostrophic surface speeds (more 20 cm/s) are observed. The ACC axis position changes near latitude 50ºS in the Atlantic and the Indian Oceans, and between latitude 55–60ºS in the Pacific Ocean. Thus average geostrophic surface speed along the ACC axis makes 16 cm/s, and it changes from 10 to 15 cm/s on ACC borders (SAF and PF).
In spectral density sesonal variation of the ACC axis and intensity are looking good independently of longitude. However interannual changes are various for different past of the Sourtern Ocean. For example they are insignificant in Darke Passeg, but near Kergelen Platoau position of the ACC axis dislocates to south with rate about 0.02 deg/yr, while the ACC intesity isn’t change almost.
The research was undertaken with partial support from the Russian Basic Research Foundation (Projects 06-05-64871 and 06-05-65061).