When it was hot in Antarctica

In some parts of the ancient Antarctica was once as warm as it is today on the coast of California and Florida. On this claim scientists in their research using a new method of measuring the temperature in the past.

The findings, published in April in the Proceedings of the National Academy of Sciences of the United States, stressing the potential to raise the temperature of the Earth's poles, as well as the associated risk of melting of the polar ice caps and rising sea levels.

The study led by researchers from Yale University, focused on Antarctica in the Eocene epoch, 40-50 million years ago, during the period with a high concentration of CO2 in the atmosphere and, therefore, is under the influence of the greenhouse effect. Today Antarctica throughout the year is one of the coldest places on Earth, with an average temperature below zero even during the warm summer months.

But it was not always so, and the new data will help improve climate models used to predict future climate, says one of the study's authors associate professor of geology and geophysics at Yale University Hagit Affek .

Measuring the temperature of the past helps us to understand the sensitivity of the climate system to greenhouse gases, and especially the impact of global warming on the polar regions, said Affek.

In the research team included paleontologists, geochemists and climate physicist.

Measuring the concentration of rare isotopes in ancient fossil shells, the scientists found that the temperature in some parts of Antarctica reached 17 degrees Celsius during the Eocene, with an average temperature of 14 degrees - similar to the average temperature of the coast of California today.

Eocene temperature in the South Pacific was measured 22 degrees Celsius, the researchers say, which corresponds to a temperature of sea water near Florida today.

Today, the average annual temperature of the sea in the South Pacific Ocean off the coast of Antarctica is about 0 degrees Celsius.

These ancient ocean temperatures were not evenly distributed across regions of Antarctica, and the researchers say that this finding suggests that the difference in temperature led to the ocean currents.

Measurement of past temperatures in different parts of Antarctica gives us a clear idea of ​​how warm was Antarctica, where the Earth's atmosphere contained much more CO2 said Peter Douglas , one of the study participants. Now we know that once it was warm across the continent, but in some parts it was much warmer than the other. This strongly suggests that global warming could particularly affect regions that are close to the Earth's poles. Warming in these regions has significant consequences for the climate far beyond due to ocean circulation, the melting of the polar ice caps and rising sea levels. 

To determine the temperature of the ancient scientists measured the amount of two rare isotopes associated with each other in the fossil bivalve shells collected by one of the study's authors Linda Ivan  from Syracuse University. The concentration of the links between carbon-13 and oxygen-18 reflects the temperature at which the shell has grown, the researchers say. They combined these results with other geothermal and simulation models.

We were able to combine data from different geochemical methods to the climate model to learn something new about how the Earth's climate system operates in conditions different from its current state, said Affek. This combination of different approaches provides a more complete picture than could give either of these approaches alone.