Fig. 3: ¹³⁷Cs profiles across the South Pacific (30°S), Indian (20°S) and Atlantic (30°S) Oceans during the BEAGLE (Blue Ocean Global Expedition (2003–2004).
From: Anthropogenic radionuclides as tracers of climate change in the Pacific Ocean
The Indian Ocean exhibits pronounced subsurface 137Cs maxima at 100–200 m (notably near 100°E and 55°E), representing the highest 137Cs concentrations observed in the Southern Hemisphere, which are comparable to maxima in the North Pacific. These data confirm the transport of surface waters from the North Pacific through Indonesian seas into the South Indian Ocean and then to the subtropical gyre, which serves as a long-term reservoir of anthropogenic pollutants on decadal timescales. Similar upper-ocean concentrations in the SW Indian Ocean and the South Atlantic Ocean indicate inter-basin exchange via the Agulhas system and the broader overturning circulation associated with the GMOC. The North Pacific therefore acts as a source of anthropogenic radionuclides and other pollutants to the South Indian and South Atlantic Oceans. Adapted from ref. 20, licensed under CC BY).
