Abrupt changes in high-latitude nutrient supply to the Atlantic during the last glacial cycle
The supply of nutrients to the low-latitude thermocline is largely controlled by intermediate-
depth waters formed at the surface in the high southern latitudes. Silicic acid is an essential
macronutrient for diatoms, which are responsible for a signifi cant portion of marine
carbon export production. Changes in ocean circulation, such as those observed during the
last deglaciation, would infl uence the nutrient composition of the thermocline and, therefore,
the relative abundance of diatoms in the low latitudes. Here we present the fi rst record
of the silicic acid content of the Atlantic over the last glacial cycle. Our results show that
at intermediate depths of the South Atlantic, the silicic acid concentration was the same at
the Last Glacial Maximum (LGM) as it is today, overprinted by high silicic acid pulses that
coincided with abrupt changes in ocean and atmospheric circulation during Heinrich Stadials
and the Younger Dryas. We suggest these pulses were caused by changes in intermediate
water formation resulting from shifts in the subpolar hydrological cycle, with fundamental
implications for the nutrient supply to the Atlantic.
Authors: Hendry, K.R., Robinson, L.F., Meredith, Michael ORCID record for Michael Meredith, Mulitza, S., Chiessi, C.M., Arz, H.