According to a detailed analysis of the ancient Antarctic ice layer, researchers found that the growth rate of atmospheric carbon dioxide today is 10 times that of any time in the past 50000 years. Recently, relevant achievements were published in the Journal of the National Academy of Sciences.
This study provides new knowledge for the study of the abrupt climate change period in the earth's history, and puts forward new ideas on the potential impact of climate change today.
"Research in the past can tell us how different today is. Today's rate of change of carbon dioxide is indeed unprecedented." Kathleen Wendt, the main author of the paper and assistant professor of Oregon State University, said, "Our research has determined the fastest rate of natural rise of carbon dioxide in history, and today's carbon dioxide emissions, mainly driven by humans, are 10 times faster than in the past."
In the past, carbon dioxide levels fluctuated due to glacial cycles and other natural causes. But today, due to human emissions, carbon dioxide levels are rising.
The ice formed in Antarctica for hundreds of thousands of years contains ancient atmosphere, which is trapped in bubbles. Scientists collected these ice samples by drilling 3.2km deep ice cores to analyze trace chemicals and establish past climate records.
Previous studies have shown that during the last ice age, which ended about 10000 years ago, carbon dioxide levels in several stages appear to be far above average. But these measurements are not accurate enough to reveal the full nature of rapid change.
"Our interest has been stimulated, and we want to go back to those periods for more detailed measurements to understand what happened," Wendt said.
Wendt and colleagues used ice core samples from the boundary line of the Great Ice Sheet in West Antarctica to study what happened in those periods. They found a model that indicates that these carbon dioxide surges occurred in the cold period of the North Atlantic called Heinrich event, which is related to climate change around the world.
"These Heinrich events are really extraordinary." said Christo Buizert, one of the authors of the paper and an associate professor at Oregon State University. "We believe that they were caused by the rapid collapse of the North American ice sheet. This triggered a series of chain reactions, including changes in the tropical monsoon, the southern hemisphere westerly wind and a large amount of carbon dioxide in the ocean."
During the maximum natural rise period, carbon dioxide has increased by about 14 ppm (parts per million) in 55 years. This surge occurs about every 7000 years. According to the rising rate of carbon dioxide today, the growth of this scale can be completed in only five to six years.
There is evidence that during the natural rise of carbon dioxide in the past, the westerly wind, which plays an important role in the deep ocean circulation, is also strengthening, leading to the rapid release of carbon dioxide in the Southern Ocean.
Other studies show that these westerlies will strengthen in the next century due to climate change. The researchers point out that the new findings show that if this happens, it will reduce the ability of the Southern Ocean to absorb carbon dioxide generated by humans.
"We rely on the Southern Ocean to absorb some of the carbon dioxide emitted by humans, but the rapidly increasing southerly wind has weakened this ability," Wendt said. (WenLeLe)
Relevant paper information:
https://doi.org/10.1073/pnas.2319652121
