A team of researchers led by scientists from the University of Victoria of Wellington (NZ) and Birmingham (UK) recently published the first record of Antarctic Ocean temperatures over the past 45 million years, which provides important insights into future sea level changes. To track changes in sea temperature, they used a combination of data obtained from molecular fossils and machine learning.
The molecular fossils were obtained from core samples obtained from ocean drilling projects. Inside these cores were the fossilized remains of lipid molecules produced by archaea, single-celled organisms similar to bacteria. Lipid molecules were part of the body’s outer membrane, and the composition of these molecules changed with differences in sea temperature. By studying these changes, scientists can draw conclusions about the temperature of the ancient sea that surrounded the Archaea when they were alive.
While the use of molecular fossils is familiar to paleoclimatologists, current researchers have gone further and used machine learning to refine the technique. This allowed them to obtain the first data to date on the change in temperature of the Antarctic Sea over the past 45 million years, which is most of the Cenozoic period.
The results of the study, published in the journal Nature Geoscience, allow scientists to more accurately determine the historical temperatures that caused the rise and fall of ice sheets during this period. This is very important for our understanding of the possible consequences of the current global warming, as the loss of ice sheets and the retreat of glaciers in Antarctica could mean a sea level rise of up to 50 meters.
“Our data provides a better understanding of temperature fluctuations in Antarctica and how they relate to changes in Antarctic ice and landforms over this period, and paves the way for more accurate estimates of future events,” said study lead author Dr. James Bendl. .
The relationship between CO2, sea surface temperature and ice levels in Antarctica is clearly supported by research data over the past 45 million years. But one surprising result was that the cooling of the ocean did not always match the increase in Antarctic ice. In particular, this applies to the 1-million-year period of ocean cooling that occurred between 25 and 24 million years ago. “We show that this is likely due to tectonic subsidence and inflow of relatively warm ocean water in the Ross Sea region,” said Dr. Bendl.
“We see that the ice in Antarctica is currently changing, not least due to the loss of some ice shelves and recent cracks in the Thwaites Glacier, one of the largest glaciers in the region.”
This new study of the Earth’s past is one of the clearest indications that humans continue to produce CO2 at levels where we can expect large ice loss on the Antarctic margins and global sea level rise in the coming decades and centuries.”
The researchers say their results suggest a “tipping point” is approaching, when ocean warming caused by atmospheric CO2 will lead to catastrophic sea level rise due to melting ice sheets. They plan to continue applying biomarker-based and machine learning approaches to reconstruct the climate evolution of Antarctica and understand the implications of future warming and sea level rise.