Scientists released fluorescent dye nearly 2 km underwater; it revealed deep water rising 100 metres a day

A fluorescent green dye released nearly 1,870 metres below the surface of the North Atlantic has helped scientists directly observe a long-suspected movement of deep ocean water, and the water was rising far faster at the study site than the global average previously estimated.In an experiment conducted in 2021, researchers released about 55 gallons of non-toxic fluorescein dye close to the seafloor inside a submarine canyon in the Rockall Trough, roughly 370 kilometres northwest of Ireland. By tracking the dye as it moved through the deep water, the team found evidence of vigorous upward mixing along the canyon slope.The measured upwelling was of the order of 100 metres per day, around 10,000 times the global average rate required to sustain the ocean's large-scale overturning circulation, according to the study published in Nature in June 2024. The finding addresses a long-standing question in oceanography: how does cold, dense water that sinks into the deep ocean eventually return towards the surface?A mystery hidden deep beneath the oceanThe world's oceans are constantly moving heat, carbon and nutrients through a vast circulation system. Cold, dense seawater forms at high lati...