The global climate of the Earth changed dramatically in the past and will change in the future. Reconstructing past climate conditions is a challenging task, yet crucial to understand the complexity of the Earth’s climate system. The global ocean circulation is a fundamental component in the Earth’s climate system, as it stores and re-distributes heat and matter such as carbon, oxygen and nutrients on the planet.

But how did the global ocean circulation evolve in the past? Did water masses flow the same paths as today? Have there been changes in water mass exchange across the hemispheres? What happened during major climate changes?

Answering these questions is a challenge, however authigenic neodymium isotopes (εNd) preserved in the coating of sediment particles in the deep sea have proven useful to study the deep ocean circulation and water mass provenance of the past.

There are little high resoluted and far back reaching εNd records available. The unprecedented 1 Ma εNd record of high resolution from a site situated south of the Polar Front in the Atlantic Ocean presents an important benchmark, which shows a variable behavior synchronous with climate an is of special interest over major climate changes in the past.

Based on the strong correlation of εNd with climate a new tool for the age model of the sediment could be developed. Further, the interplay of advective and diffusive processes influencing the εNd signatures and likely the entire Southern Ocean was studied. Together with several εNd records from the Atlantic the interhemispheric εNd gradient provides insights in the evolution of the deep water exchange over the past one million years.

N summary, the new εNd data take us one step further on finding the answer to the proposed questions and highlight the applicability of εNd as a water mass tracer but also as a new tool to evaluate the interhemispheric deep water mass exchange in the past.