Multistage process of North Pacific cooling during the past 10 million years

Earth’s climate and ocean circulation have reorganized profoundly since the late Miocene. Global compilations of sea surface temperature reconstructions indicate cooling trends during the late Miocene and the Pliocene-Pleistocene periods. However, there is no long-term high-resolution temperature record from the northwestern Pacific yet. Here we present a new, extremely high-resolution (1-3 kyr), continuous alkenone sea surface temperature record spanning the past 10 million years from the subarctic front region of the northwestern Pacific. On glacial-interglacial timescale, SST variance and dominant frequencies changed stepwise, defining three phases: strong-amplitude variability (~5–9°C) at 0–1.7 Ma, moderate variability (~2–5°C) at 1.7–5.6 Ma, and weak variability (~1–2°C) at 5.6–9 Ma. Band-pass filtering isolates 405, 100, 41 and 21/19 kyr components, revealing pervasive orbital pacing and reproducing the three-phase structure. On long-term timescale, our results exhibit multistage process of the North Pacific cooling with related climate changes during the time period. In particular, the late Miocene (5-7 Ma) cooling can be compared with that of the late Pliocene-Pleistocene periods (1-3 Ma). Further comparisons between our temperature record at the subarctic front region with those from the western and eastern equatorial Pacific have been conducted, anticipating being able to reconstruct the evolution/variability of the subarctic front and its relationship with the evolution of the North Pacific subtropical gyre during the northern hemisphere glaciation.