Taking advantage of the unique properties of sediments from the bottom of Sawtooth Lake in the Canadian high-altitude Arctic, climatologists have set a new record for sea surface temperatures in the Atlantic Ocean over the past 3000 years. The research results are published by the Proceedings of the National Academy of Sciences.
A team led by François Lapoant and Raymond Bradley of the University of Massachusetts Climate Systems Research Center at Amherst and Pierre Francus of the University of Quebec analyzed “perfectly preserved” annual sediment layers that had accumulated in a lake in the north of Ellesmere Island, Nunavut. The peculiarity of these deposits is that they contain titanium, which remained after centuries of weathering of rocks. By measuring the concentration of titanium in different layers, scientists can estimate the relative temperature and atmospheric pressure that has been observed over time.
After examining the deposits, scientists found that the lowest temperatures were found between 1400-1600 AD, with the warmest interval only observed in the last decade.
Our unique dataset represents the first reconstruction of the surface temperature of the Atlantic Ocean in 3,000 years and will enable climatologists to better understand the mechanisms behind long-term changes in Atlantic Ocean behavior.
Pierre Francus of the University of Quebec
When cold temperatures prevail over the North Atlantic, relatively low atmospheric pressure is observed in most of the Canadian highlands of the Arctic and Greenland. This is due to the slower melting of snow in this region and the higher titanium content in the sediments. The reverse is also true – the warmer the ocean, the higher the atmospheric pressure, the snow melts faster, and the titanium concentration decreases.
“Using these strong connections, it was possible to reconstruct how the surface temperature of the Atlantic Ocean has changed over the past 2,900 years, making this record the longest currently available,” explains Lapointe.
The researchers report that their recently recovered data correlates significantly with several other independent records of sediment in the Atlantic Ocean, from northern Iceland to the coastal regions of Venezuela. This confirms their reliability as a proxy for long-term ocean temperature variability. Scientists note that the new record is also similar to European temperatures over the past 2,000 years.
Lapointe, who has conducted extensive fieldwork in the Canadian Arctic over the past decade, notes that “in recent summer, this region is usually dominated by systems with high atmospheric pressure – clear sky conditions. Maximum temperatures often reach 20 degrees Celsius for days or even weeks in a row, like in 2019. This has had an irreversible effect on snow cover, glaciers and ice caps, as well as on permafrost. ”
“These conditions are currently not adequately reflected in global climate models, which underestimates the potential consequences of future warming in the Arctic regions,” the scientists conclude.