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Glaciers may grow and shrink faster than expected
Drowned passage decorated with speleothems, Vallgornera Cave, Spain.
[Image © Tony Merino]
During the last ice age, the world's sea level fell by approximately 130 meters. For about 100,000 years, it dropped—but not smoothly—with a series of small spikes back up along the way. Now, new research shows that the world's sea level 81,000 years ago was actually more than a meter higher than it is today.
Since the sea rises and falls with the melting and forming of glaciers, respectively, this finding means that the polar ice sheets were smaller and global temperatures were at least as high (or even higher) 81,000 years ago than they are now—even though the concentration of carbon dioxide in the atmosphere was much lower back then.
Encrusted stalactites at present sea level, Vallgornera Cave, Spain.
[Image © Bogdan P. Onac]
This finding does not agree with traditional theories of how ice sheets form. Instead, it suggests that glaciers may grow and shrink faster than experts have believed, and if they are confirmed, the results of this study are sure to change the debate over how ice ages come and go.
In order to reach these new conclusions, Jeffrey Dorale and colleagues took measurements from a cave formation on the Spanish island of Mallorca. The cave formation that the researchers analyzed has been submerged in the Mediterranean Sea on-and-off for hundreds of thousands of years.
According to Dorale and colleagues, the 100,000-year cycle that researchers have come to rely upon might not apply to glaciers after all. Instead, they suggest it might only apply to carbon dioxide levels, methane levels, and global temperatures recorded by polar ice caps.