Seashells point to much warmer past: scientists

Three to four million years ago the temperatures on Ellesmere Island’s Strathcona fiord were up to 16 C higher than today. (PHOTO BY MARTIN LIPMAN)

By studying fossilized seashells from 3.5 million years ago, scientists from the University of California in Los Angeles have constructed an ancient climate record for Ellesmere Island.

Their research shows that, during this period, temperatures were considerably higher in the High Arctic than today.

Three to four million years ago, temperatures from May to September were 11 to 16 C warmer there than the present-day average temperatures of −1.6 to 1.3 C.

From studying fossil seashells and plants gathered around Ellesmere Island’s Strathcona Fiord, scientists determined that the average growing-season temperature on Ellesmere Island reached about 11 C.

The results of the new study, detailed in the online edition of Earth and Planetary Science Letters, suggests how global warming due to higher levels of greenhouse gases in the atmosphere will impact the High Arctic.

The study reveals what may happen when levels of the greenhouse gas carbon dioxide stabilize at about 400 parts per million — as was the case when those shells were formed and plants thrived 3.5 million years ago in a much warmer, ice-free Strathcona Fiord.

The Intergovernmental Panel on Climate Change has said keeping carbon dioxide levels at 400 ppm, by reducing greenhouse gas emissions world-wide, will keep global temperature rise to two degrees Centigrade.

Previous research has shown that, for the High Arctic, this 2 C rise will still mean temperatures up to 16 C higher in the Arctic than today by 2100.

Shells collected from Beaver Pond in Strathcona Fiord provided the materials scientists looked at for this recent study.

Named for the numerous branches discovered with beaver teeth marks, which have lasted for millions of years, Beaver Pond contains many plant and animal specimens which are well-preserved within a peat layer encased in ice.

By measuring the oxygen in a combination of fossilized shells and plant samples, it was possible to determine the temperature at which the specimens originally formed, said Aradhna Tripati, from ULCA’s department of earth and space sciences, in an April 7 news release.