234Th is a naturally occurring radionuclide constantly produced in sea water by its soluble parent 238U. Due to its high reactivity to particles and relatively short half-life (T1/2 = 24.1 days), 234Th is used as an effective and suitable proxy for describing biogeochemical processes occurring over timescales of days to weeks in the upper water column.In a rapidly changing environment, akin to the water column during the Antarctic spring-summer transition, a study of short timescale alterations of the 234Th/238U equilibrium can significantly improve the understanding of the forces driving exceptional events such as an incipient phytoplankton bloom