About 100,000 years ago, when mammoths roamed the earth, temperatures plummeted in the northern hemisphere and large areas were covered by massive ice sheets.
In just 10,000 years, local mountain glaciers formed huge ice sheets, covering large parts of what is today Canada, northern Europe, and Siberia.
Therefore, Palo climatologists have long worked to find answers to two questions: Where did the ice sheets that dominated during the last ice age come from? And how could they grow so massive so fast?
In new study may have the answers.
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The earth’s orbit around the sun determines ice ages
Ice ages are dictated by the earth’s orbit around the sun. The trajectory can vary from being elliptical to being almost completely round. At the same time, small changes occur in the angle of the earth’s axis.
These variations affect the amount of solar radiation that reaches the earth’s surface. Thus, it matters how hot or cold it gets on earth.
The changes are called glacial cycles and the most recent began 116,000 years ago, after which a huge and massive ice sheet eventually covered the northern hemisphere.
It did not take the ice sheets more than 10,000 years to melt together.
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Scandinavia should be ice-free
While it may seem likely that the areas that are today Canada and Siberia were covered by ice, the experts have put their foreheads in deep folds when they have tried to explain the extensive ice sheets that covered the milder regions of Scandinavia and the rest of Northern Europe.
The warm waters that the North Atlantic ocean current brings with it should have helped to keep Scandinavia largely ice-free.
To find the answer, the researchers developed a complex analysis model called the Community Earth System Model. The model was able to recreate the climatic conditions that prevailed at the beginning of the last ice age.
Then the researchers discovered that passages in the Canadian, Arctic archipelago formed an important hub for control of the North Atlantic climate, which ultimately decided whether ice sheets could be formed in Scandinavia or not.
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The ice cover controls ocean currents
The models developed by the researchers revealed that as long as the passage of the Canadian Arctic archipelago was kept open, the northern hemisphere cooled down enough to build up ice sheets in northern Canada and Siberia, but not in Scandinavia.
However, the researchers discovered that if the waterways in the Canadian Arctic archipelago were blocked, the healthy Arctic and northern Pacific waters would be redirected eastward via passages outside Greenland.
The researchers have since been able to support the new models with studies of sea sediments from the North Atlantic, which show signs of glaciers in northern Canada thousands of years before those that originated in Europe.
The sediment studies also showed a weakened deep-sea circulation before the glaciers formed in Scandinavia.
The formation of sea ice in northern Canada has therefore been a prerequisite for an ice age to occur in Scandinavia – and for it to happen so rapidly.
The new method for calculating ice ages is so groundbreaking that it can be used to investigate and understand other historical ice ages. At the same time, it can help predict future climate change with greater precision.
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