Neodymium Evidence for Increased Circumpolar Deep Water Flow to the North Pacific During the Middle Miocene Climate Transition

• Published in: Paleoceanography and paleoclimatology Vol. 33; no. 7; pp. 672 - 682
• Main Authors: Kender, Sev, Bogus, Kara A., Cobb, Ty D., Thomas, Deborah J.
• Format: Journal Article
• Language: English
• Published: Hoboken Blackwell Publishing Ltd 01-07-2018
• Subjects: Circumpolar Deep Water; Climate; Cold water; Constraint modelling; Deep water; Fish; Fish teeth; Glaciation; Ice sheets; Isotopes; Mass; Miocene; Neodymium; Neodymium isotopes; Neogene; Oceans; Pacific meridional overturning circulation; Philippine Sea; Sinking; Surface water; Teeth; Tracers; Water depth; Water flow; Water masses; Water temperature; Pacific Ocean
• ISSN: 2572-4517; 2572-4525
• DOI: 10.1029/2017PA003309

Low salinity surface water inhibits local deepwater formation in the modern North Pacific. Instead, southern‐sourced Circumpolar Deep Water (CDW) fills the basin, which is the product of water masses formed from cold sinking centers in the Southern Ocean and North Atlantic. This CDW is responsible for transporting a significant amount of global heat and dissolved carbon in the deep Pacific Ocean. The history of its flow and the broader overturning circulation are widely assumed to be sensitive to climate perturbations. However, insufficient records exist of CDW presence in the deep North Pacific with which to evaluate its evolution and role in major climate transitions of the past 23 Ma. Here we report sedimentary coatings and fish teeth neodymium isotope values—tracers for water‐mass mixing—from deepwater International Ocean Discovery Program Site U1438 (4.7 km water depth) in the Philippine Sea, northwest Pacific Ocean. Our results indicate the water mass shifted from a North Pacific source in the early Miocene to a southern source by ~14 Ma. Within the age model and temporal constraints, this major reorganization of North Pacific water mass structure may have coincided with ice sheet build up on Antarctica and is most consistent with an increased northward flux of CDW due to enhanced sinking of cold water forced by Antarctic cooling. The northward extent of this flux may have remained relatively constant during much of the past 14 Ma.
Key Points
We present the first record of fish teeth and sedimentary coating neodymium isotopes from the abyssal Philippine Sea (North Pacific) during the Neogene
This Deep Pacific water mass shifted from a North Pacific source in the Early Miocene to a southern source by ~14 Ma
This major reorganization of North Pacific water mass structure may have been linked with Antarctic glaciation of the middle Miocene climate transition