Southern Ocean source of ¹⁴C-depleted carbon in the North Pacific Ocean during the last deglaciation

During the last deglaciation, atmospheric carbon dioxide concentrations rose at the same time that the Δ 14 C of that CO₂ fell. This has been attributed to the release of 14 C-depleted carbon dioxide from the deep ocean, possibly vented through the Southern Ocean. Recently, a sediment record from the eastern North Pacific Ocean spanning the last deglaciation was interpreted to reflect transport of such radiocarbon-depleted CO₂ from the Southern Ocean through Antarctic Intermediate Water. However, the suggestion that the record reflects intermediate water derived from the Southern Ocean remains controversial. Here we assess the source of the deglacial intermediate water by measuring the neodymium isotopes of fossil fish teeth/debris from the same eastern North Pacific core used in the earlier study. The isotopic signature of a water mass, which is captured in the fossil fish teeth, reflects the location in which it formed. Our data exhibit a clear shift in the neodymium isotope values towards Southern Ocean values about 18,000 years ago, coinciding with the negative Δ 14 C excursion. We conclude that these data support a Southern Ocean source for the deglacial radiocarbon-depleted CO₂ detected in the eastern North Pacific.