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New Research Illuminates Ancient Ocean Currents and Climate Change

A international study has unveiled new insights into the evolution of deep ocean currents and their impact on Earth's climate.

20 May 2025
a huddle of people around a table in the hull of a ship

Dr Tom Dunkley Jones (centre) with crew on the International Ocean Discovery Program (IODP) Expedition 395 in 2023

A groundbreaking international study, featuring contributions from the University of Birmingham, has unveiled new insights into the evolution of deep ocean currents and their impact on Earth's climate. Published in Nature Communications on May 9, 2025, the research reveals that the Iceland–Scotland Overflow Water (ISOW), a crucial component of the North Atlantic Deep Water (NADW), intensified around 3.6 million years ago—earlier than previously believed.

The NADW plays a vital role in the Atlantic Meridional Overturning Circulation (AMOC), a system that significantly influences global climate patterns. By analysing sediment cores collected during the International Ocean Discovery Programme (IODP) Expeditions 395C and 395, the research team identified a rapid acceleration in sediment deposition associated with ISOW at the 3.6-million-year mark. This finding suggests a pivotal shift in deep ocean circulation that likely contributed to the long term evolution of Northern Hemisphere climate.

Dr. Tom Dunkley Jones from the University of Birmingham's School of Geography, Earth and Environmental Sciences played a key role in this study. His expertise in the study of marine algae was instrumental in interpreting the sedimentary records that underpin these conclusions.

Understanding the historical behaviour of ocean currents like ISOW is essential for predicting future climate scenarios," said Dr. Dunkley Jones. "Our findings provide a clearer picture of how deep water formation and circulation have evolved, offering valuable context for current climate models

Dr. Tom Dunkley Jones

The study was led by Dr Matthias Sinnesael from Trinity College Dublin’s School of Natural Sciences and Dr Boris Karatsolis from Vrije Universiteit Brussel. 

In recent decades, humanity has increasingly felt the impacts of global warming. From rising sea levels that endanger coastal cities to heatwaves and floods, the world is currently living within the ‘storm’ of extreme weather events. Collectively, the short-term daily-to-monthly changes in weather that persist over long periods, eventually become part of the climate, which constitutes the long-term average state of these weather conditions. At the same time, changes in climate can act in timescales larger than humanity itself, influenced by complex interactions between various processes like plate tectonics, greenhouse gases, biotic evolution, and ocean circulation patterns.

Dr Matthias Sinnesael, Trinity College Dublin’s School of Natural Sciences

The study also highlights a contrast between ISOW and the Denmark Strait Overflow Water (DSOW), another NADW component. While ISOW showed significant intensification 3.6 million years ago, DSOW has exhibited a more consistent presence since the Late Miocene. This divergence underscores the complex nature of oceanic systems and their varied responses to climatic shifts.

These insights not only enhance understanding of past climate dynamics but also underscore the importance of ocean currents in regulating Earth's climate.

Featured staff

  • Dr Tom Dunkley Jones

    Birmingham Fellow

    School of Geography, Earth and Environmental Sciences

    Dr Tom Dunkley Jones, Royal Society Dorothy Hodgkin Research Fellow and Birmingham Fellow at the University of Birmingham. Tom is a micropalaeontologist specializing in the study of fossil coccolithophore algae.

    Phone: +44 (0)121 414 6751
    Email:

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