A simple mixing explanation for late Pleistocene changes in the Pacific-South Atlantic benthic δ 13 C gradient

• Published in: Climate of the Past
• Main Author: L. E. Lisiecki
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2010
• Subjects: Environmental pollution; TD172-193.5; Environmental protection; TD169-171.8; Environmental sciences; GE1-350; Southern Ocean; Pacific
• Online Access: https://doi.org/10.5194/cp-6-305-2010; https://doaj.org/article/3aa8fab1509946ff88a292627d4eeb32

The fact that the deep-ocean benthic δ 13 C minimum shifted from the North Pacific to the South Atlantic during the Last Glacial Maximum is often interpretted as evidence of a change in deep water circulation, such as the development of deep water ventilation in the North Pacific or a decrease in Southern Ocean overturning. This study re-evaluates the implications of changes in benthic δ 13 C gradients by comparing Pacific Deep Water (PDW) δ 13 C measurements with the values expected for the null hypothesis that PDW ventilation sources remained unchanged throughout the Late Pleistocene. The δ 13 C compositions of PDW, Northern Component Water (NCW) and Southern Component Water (SCW) are estimated from regional benthic δ 13 C stacks of 3–6 sites. Changes in PDW δ 13 C and PDW-SCW δ 13 C gradients over the past 800 kyr are found to be well described by a constant mixture of 60% NCW and 40% SCW plus a constant Pacific remineralization offset of −0.5‰. Thus, a change in PDW ventilation cannot be inferred solely on the basis of changes in the Pacific-South Atlantic benthic δ 13 C gradient.