A new study led by University of Arizona researchers may solve two mysteries that have long puzzled paleoclimate experts: Where did the last ice age ice sheets come from, and why they grew so much more than 100,000 years ago fast? Understanding what drives Earth’s glacier-interglacial cycle — the periodic advance and retreat of ice sheets in the northern hemisphere — has been no easy task, and researchers have put a lot of effort into explaining the expansion and contraction of large ice blocks over thousands of years. The new study , published in the journal Nature Geoscience, proposes an explanation for the rapid expansion of ice sheets that covered much of the northern hemisphere during the most recent ice age, and the findings may also apply to Other Ice Ages.
About 100,000 years ago, mammoths were still roaming the earth, and the climate in the northern hemisphere cooled sharply, leading to the formation of large ice sheets. Over a period of about 10,000 years, local mountain glaciers grew and formed a large ice sheet that covered much of what is today Canada, Siberia, and northern Europe. Scientists have been unable to explain the large ice covering Scandinavia and much of northern Europe, although it is widely believed that periodic “wobbles” in Earth’s orbit around the sun trigger the cooling of the northern hemisphere summer, leading to the onset of widespread glacial action. Cover, it’s much warmer there. “Using climate model simulations and ocean sediment analysis, we demonstrate that ice formation in northern Canada blocks ocean pathways that allow seawater to flow from the Arctic into the North Atlantic,” said Marcus Lofverstrom, assistant professor of geosciences and head of the UArizona Earth System Dynamics Lab. This in turn resulted in weakened ocean circulation and cold conditions off the Scandinavian coast, enough for the region to start freezing.”
“These findings are supported by the North Atlantic marine sediment record, which provides evidence that glaciers in northern Canada predate Europe by thousands of years,” said Diane Thompson, assistant professor in the Department of Earth Sciences at the University of Arizona. “The sediment record also shows that Convincing evidence that deep-sea circulation weakened before glaciers formed in Scandinavia, similar to what we modeled.” The authors write that these experiments suggest that the formation of sea ice in northern Canada may be a Necessary prerequisites for glaciation in Scandinavia. “The mechanism we’ve identified here may apply to every ice age, not just the most recent one,” Lofverstrom said. “It may even help explain shorter periods of cold, such as after the end of the last ice age, when Newer Dryas cold reversal (12,900 to 11,700 years ago) that interrupted the general warming trend.”
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