Research from the University of Sydney and Sorbonne University used the geological record of the deep sea to discover a connection between the orbits of Earth and Mars, past global warming patterns and the speeding up of deep ocean circulation. They discovered a surprising 2.4-million-year cycle where deep currents wax and wane which, in turn, is linked to periods of increased solar energy and a warmer climate.

These cycles are called “astronomical grand cycles”, predicted to occur due to the interactions of Earth and Mars orbits. However, evidence for this is rarely detected in the geological record.

The study has identified that deep eddies were an important component of earlier warming seas. It is possible these could partly mitigate ocean stagnation some have predicted could follow a faltering Atlantic meridional overturning circulation that drives the Gulf Stream and maintains temperate climates in Europe.

How the interplay between different processes driving deep-ocean dynamics and ocean life may play out in the future is still not well known, but the authors hope that their new results will help with building better climate models.