Abrupt changes in the supply of Southern Ocean nutrients to the Atlantic across the last deglaciation

There is an increasing body of evidence pointing towards dramatic changes in ocean circulation during the abrupt climate events of the last deglacial linked with increases in atmospheric CO2 recorded in ice-cores. Shifts in the nature and geographical extent of intermediate water supply from the Southern Ocean, which feeds nutrients such as silicic acid into the thermocline, would have significant implications for biological productivity in the Atlantic. Here, we present records of sponge spicule silicon isotopes, a measure of silicic acid concentration, from intermediate depths of the western Atlantic. The records show Si-rich southern sourced waters invaded the mid-depths of the South Atlantic during the periods of abrupt climate change during the late glacial and deglacial, and can be traced to intermediate depths of the North Atlantic. We suggest these pulses of Si-rich waters fed diatom and radiolarian production into the high latitude North Atlantic. We also present records of biogenic opal separated from Bermuda Rise sediments, in the North Atlantic, at times of high opal burial during Heinrich Event 1. Our records of changes in intermediate depth waters provide direct evidence for large adjustments in ocean circulation during the periods of rapid climate change and atmospheric CO2 increase.