Molecular fossils and machine learning have enabled scientists to build the first charts of Antarctic ocean temperatures over the past 45 million years.
The team, led by scientists from Victoria University of Wellington (NZ) and Birmingham (UK) say their results suggest we are nearing a ‘tipping point’ where ocean warming caused by atmospheric CO 2 will cause catastrophic rises in sea levels because of melting ice sheets. Their results are published today (15 September 2022) in Nature Geoscience.
In the study, the team examined molecular fossils from core samples taken during ocean drilling projects. The fossil remains are in fact single lipid (insoluble in water) molecules produced by archaea - single-celled https://www.nature.com/articles/s41561-022-01025-x which are similar to bacteria. The archaea adjust the composition of their outer membrane lipids in response to changing sea temperatures. By studying these changes, scientists can draw conclusions about the ancient sea temperature which would have surrounded a particular sample as it died.
While these molecular fossil techniques are well used by palaeoclimatologists, the team from Wellington (NZ) and Birmingham (UK) went a step further. They used machine learning to refine the technique, giving the first record to date of changing Antarctic sea temperatures throughout much of the Cenozoic period – covering the past 45 million years.
That means scientists are able to pinpoint much more accurately the historic temperatures which caused ice sheets to grow and shrink during that period. The future loss of ice sheets and the retreat of glaciers in the Antarctic is critically important as melting ice in the region could sea levels to rise by up to 50 m.