25th February 2020: How beautiful would it be to nearly feel the complex ACC system under our feet in the vast Southern Ocean?

by Maria de la Fuente and Gwen Jouet

Around Antarctica region there is a strong current called Antarctic Circumpolar Current (ACC) going clockwise and achieving speeds of 100-150 Sv (hm3/s). Several sharp changes in both temperature and salinity are present in the surface waters as we go further south in the current, the so-called ‘Fronts’.

Onboard the Marion Dufresne research vessel in the ACCLIMATE-2 Southern Ocean mission we have been able to cross and identify the ACC fronts through the constant hydrographical measurements carried by the various sensors placed at the base of the ship. Follow our daily measurements here.

The upper figure shows the Sea Surface Temperature (SST) changes registered along the cruise and the lower figure displays the location of the main sampling stations towards south. Taken together, these figures show how the recorded changes in SST over our days of navigation are in good agreement with the Fronts crossing timing. Thus, the SST consistently decreased as we left Durban city between 27-20ªC until entering the ACC system where we experienced a sharp ~10ºC drop in the surface temperature in just 500 km. Once in the ACC, the SST changes were less pronounced but perfectly noticeable between fronts… very nice!