Using six autonomous Argobuoys, Ukrainian scientists have carried out the first-ever year-round oceanographic study in the Bransfield Strait between the Antarctic Peninsula and the South Shetland Islands. Since their deployment in March 2025, the measuring stations have been continuously providing data on the temperature and salinity of the seawater – even during the Antarctic winter.
The Argobuoys descend to a depth of 1,500 metres and drift with the ocean currents. Every ten days, they rise slowly to the surface, measuring the temperature and electrical conductivity at every metre of water depth – data from which the salinity can be calculated. Once they resurface, they have only around 20 minutes to transmit their data to the scientists via satellite. To avoid collisions with sea ice, the buoys are programmed not to surface when the water temperature is below –1.75 °C.
The measuring stations are located in Bransfield Strait, a dynamic and, as yet, largely unexplored region of the ocean. Here, the cold, less saline water masses of the Weddell Sea meet the warmer and more saline waters to the west of the Antarctic Peninsula. One of the buoys did not transmit for several months, but later resurfaced and transmitted its stored data. It is thought to have been trapped under thick sea ice during this time.
In just over a year, 428 data sets have already been received. For the first time, these provide a complete insight into the seasonal changes in the water masses of this region. Among other things, the researchers were able to detect the formation of seasonal surface water layers, changes in water stratification at greater depths, and permanently stable water masses.
“If we compare water masses to a garden, then alongside the green of summer we have finally seen the other seasons too: how leaves form buds, turn yellow and eventually fall off,” says oceanographer Natalia Dikul from the National Antarctic Scientific Centre (NASC), describing the new findings.
The data collected provides important insights into the Antarctic ecosystem. The upwelling of nutrient-rich deep water promotes the growth of phytoplankton – the food source for krill, fish, seabirds and seals. At the same time, warmer deep water can accelerate the melting of the ice shelves. Furthermore, the measurements provide valuable information about heat transport in the Southern Ocean and its influence on the Antarctic climate.
The research is part of the OCEAN project, which is funded under the EU’s Horizon Europe research programme in collaboration with UK Research and Innovation (UKRI).
Heiner Kubny, PolarJournal