Do you see the bubbles in this piece of Antarctic ice? It comes from a core sample. The bubbles contain carbon dioxide and other gases that were trapped in the ice when formed thousands of years ago. Researchers carefully crush the piece and capture the gases that escape when the bubbles break. This allows them to better understand what carbon dioxide levels were over time. Click on image for full size (588 Kb) Courtesy of Oregon State University

In recent years, public discussion of climate change has included concerns that increased levels of carbon dioxide will contribute to global warming, which in turn may change the circulation in the Earth's ocean, with potentially disastrous consequences.

In a paper published today in the journal Science, researchers presented new data from their analysis of ice core samples and ocean deposits dating as far back as 90,000 years ago and suggest that warming, carbon dioxide levels and ocean currents are tightly inter-related. These findings provide scientists with more data and insights into how these phenomena were connected in the past and may lead to a better understanding of future climate trends.

With support from the National Science Foundation, Jinho Ahn and Edward Brook, both geoscientists at Oregon State University, analyzed 390 ice core samples taken from Antarctic ice at Byrd Station. The samples offered a snap shot of the Earth’s atmosphere and climate dating back between 20,000 and 90,000 years. Sections of the samples were carefully crushed, releasing gases from bubbles that were frozen within the ice through the millennia. These ancient gas samples were then analyzed to measure the levels of carbon dioxide contained in each one.

Ahn and Brook then compared the carbon dioxide levels from the ice samples with climate data from Greenland and Antarctica that reflected the approximate temperatures when the gases were trapped and with ocean sediments in Chile and the Iberian Peninsula. Data from the sediments provided the scientists with an understanding of how fast or slow the ocean currents were in the North Atlantic and how well the Southern Ocean was stratified during these same time periods.

The researchers discovered that elevations in carbon dioxide levels were related to subsequent increases in the Earth's temperature as well as reduced circulation of ocean currents in the North Atlantic. The data also suggests that carbon dioxide levels increased along with the weakening of mixing of waters in the Southern Ocean. This, the researchers say, may point to potential future scenario where global warming causes changes in ocean currents which in turn causes more carbon dioxide to enter the atmosphere, adding more greenhouse gas to an already warming climate.

Ahn and Brook state that a variety of factors may be at work in the future that alter the relationship between climate change and ocean currents. One potential factor is that the levels of carbon dioxide in today's atmosphere are much higher than they were during the period Ahn and Brook studied. The researchers hope that future studies of the ancient gas from a newly drilled ice core may allow a higher resolution analysis and yield more details about the timing between carbon dioxide levels and the temperature at the Earth's poles.

Text above is courtesy of the National Science Foundation

Do you see the bubbles in this piece of Antarctic ice? The bubbles contain carbon dioxide and other gases that were trapped in the ice when formed thousands of years ago. Researchers carefully crush the piece and capture the gases that escape when the bubbles break. This allows them to better understand what carbon dioxide levels were over time. Click on image for full size (588 Kb) Courtesy of Oregon State University

To learn what Earth’s atmosphere used to be like, scientists have been studying ancient air.

The ancient air is within tiny bubbles in 390 samples of ice from Antarctica. The bubbles tell what Earth's atmosphere was like 20,000 to 90,000 years ago.

Today, as the amount of greenhouse gases in Earth’s atmosphere continues to grow and the greenhouse effect gets stronger, scientists are concerned that this may cause a change in the circulation of the ocean. Comparing the data from the air bubbles with other data about what the planet was like at that time, scientists are able to learn whether this has happened in the past.

Interested in learning more about the connection greenhouse gases, climate, and ocean circulation, scientists Jinho Ahn and Edward Brook analyzed the bubbles. Sections of the samples were carefully crushed, releasing gases from the little bubbles. The level of carbon dioxide in each ancient gas sample was measured.

The scientists compared the amounts of carbon dioxide found in the ancient air with climate information about the temperature of our planet at the time when the gases were trapped in the ice. They also compared the carbon dioxide levels from the ancient air with ocean sediments in Chile and the Iberian Peninsula. The sediments preserve evidence of how fast or slow the ocean currents were.

What did they find? The data suggests that carbon dioxide levels, global warming, and ocean currents are tightly related. They found that samples of ancient air that contained more carbon dioxide were from times when Earth’s temperature was higher. They also found that these were times when ocean currents were weaker.

And if it has happened in the past, it may happen in the future, say the scientists. And changes in ocean currents could cause even more carbon dioxide to get into the atmosphere.

Do you see the bubbles in this piece of Antarctic ice? The bubbles contain carbon dioxide and other gases that were trapped in the ice when formed thousands of years ago. Researchers carefully crush the piece and capture the gases that escape when the bubbles break. This allows them to better understand what carbon dioxide levels were over time. Click on image for full size (588 Kb) Courtesy of Oregon State University

What was the atmosphere like over 20,000 years ago? Scientists have been studying ancient air to find out.

The ancient air is within tiny bubbles in 390 samples of ice from Antarctica. The bubbles tell what Earth's atmosphere was like 20,000 to 90,000 years ago.

Scientists studied how much carbon dioxide was in the bubbles. They compared the data with information about what Earth’s climate was like in the past. They also compared the carbon dioxide levels from the ancient air with information about what the ocean circulation was like at the time.

What did they find? They found that samples of ancient air that had more carbon dioxide were from times when Earth’s temperature was higher. They also found that these were times when ocean currents did not flow as quickly.

If it has happened in the past, it may happen in the future, say the scientists.  So we might see changes in ocean currents in the future as the amount of greenhouse gases continues to grow and the greenhouse effect gets stronger.