Distal and proximal controls on the silicon stable isotope signature of North Atlantic Deep Water ...

• Main Authors: de Souza, Gregory F., Slater, Richard D., Hain, Mathis P., Brzezinski, Mark A., Sarmiento, Jorge L.
• Format: Text
• Language: English
• Published: ETH Zurich 2015
• Subjects: biogeochemical cycles; silicon isotopes; meridional overturning circulation; Southern Ocean; NADW; North Atlantic Deep Water; North Atlantic
• Online Access: https://dx.doi.org/10.3929/ethz-b-000106285; http://hdl.handle.net/20.500.11850/261833

It has been suggested that the uniquely high δ30Si signature of North Atlantic Deep Water (NADW) results from the contribution of isotopically fractionated silicic acid by mode and intermediate waters that are formed in the Southern Ocean and transported to the North Atlantic within the upper limb of the meridional overturning circulation (MOC). Here, we test this hypothesis in a suite of ocean general circulation models (OGCMs) with widely varying MOCs and related pathways of nutrient supply to the upper ocean. Despite their differing MOC pathways, all models reproduce the observation of a high δ30Si signature in NADW, as well showing a major or dominant (46–62%) contribution from Southern Ocean mode/intermediate waters to its Si inventory. These models thus confirm that the δ30Si signature of NADW does indeed owe its existence primarily to the large-scale transport of a distal fractionation signal created in the surface Southern Ocean. However, we also find that more proximal fractionation of Si upwelled ... : Earth and Planetary Science Letters, 432 ...