Evidence for Long‐Term Coupling of Deep Ocean Carbon Storage and Global Climate Over the Past 4.5 Million Years

Abstract Robust evidence indicates that late Pleistocene glacial‐interglacial climate cycles are linked to periodic, orbitally‐forced changes in the partitioning of CO 2 between the deep ocean and atmosphere. The extent to which changes in deep ocean carbon storage are related to climate on longer timescales is less well understood. To address this knowledge gap, we analyze the benthic stable carbon isotope gradient between the Pacific and North Atlantic Ocean, denoted as Δ δ 13 C, which can reflect deep Pacific respired and disequilibrium carbon content. We show that Δ δ 13 C has increased as global climate cooled and ice volume grew over the past 4.5 million years. This finding is corroborated by new trace metal data from the North Pacific across the Plio‐Pleistocene, suggesting that deep ocean respired carbon content, particularly in the Pacific, has increased alongside global climate cooling over the past 4.5 million years. These observations support the view that deep ocean carbon storage is an important component of global climate during both the late Neogene and Quaternary.