Arctic Climate Variation in Late Cretaceous Sheds Light on Current Climate Change Predictions
15.02.2011 - Atmosphere & Space, Land & Geology, Flora & Fauna, Arctic
A new study conducted by scientists from the University of Southampton’s School of Ocean and Earth Science and recently published in Geophysical Research Letters had a look back at organisms preserved in marine sediments to learn more about climate variation in the Arctic during a much warmer time in the Earth’s history, the Late Cretaceous (69–76 million years ago). Their findings suggest that man-made global warming will not significantly change how already-existing natural modes of inter-annual climate variability such as El Niño Southern Oscillation and the Atlantic North Atlantic Oscillation affect climate.
While the Arctic Ocean is anticipated to become ice-free during the summer months in 15 to 50 years, the key question is to know whether an ice-free Arctic will affect atmospheric circulation and climate variability. As part of the study, the scientists analysed sediment cores from the Arctic Ocean dating back to the Late Cretaceous. The cores contain fossil remains of diatoms, tiny planktonic marine plants, which are proof that the Arctic was ice-free during the Late Cretaceous. There is also evidence of rafting, which indicates there was winter ice cover as well. By analysing the characteristics of the diatom layers and measuring their thickness, the researchers were able to reconstruct climate-driven variations in oceans over time.
The analysis suggests that the Arctic climate of the Late Cretaceous varied over multi-year timescales similar to those we see today, like the El Niño Southern Oscillation, which transmits warmer equatorial influences to higher latitudes via interactions between the ocean and atmosphere.
These findings are important in light of the ongoing debate as to whether warmin brought on by anthropogenic climate change might have an impact on the Earth's natural climate variability. For example, the findings provide evidence gainst one hypothetical scenario in which anthropogenic climate change might create a permanent El Niño state, which would result in milder European winters.
