Little ice age triggered by massive volcanic eruptions. It does rather oxymoronic that volcanic eruptions â€“ those streams of lava â€“ might have been the cause of the Little Ice Age that lasted for centuries on the earth in the Middle Ages. The conclusion was reached by the scientists at the University of Colorado Boulder and the National Center for Atmospheric Research (NCAR). They closed down on four volcanic eruptions in the tropical regions between 1275 and 1300 AD led to the subsequent cooling rsulting in an expansion of sea ice and a related weakening of Atlantic currents.
The scientists studied patterns of dead vegetation, ice and sediment core data, and powerful computer climate models.
Bette Otto-Bliesner, a NCAR scientist, said, â€œOur simulations showed that the volcanic eruptions may have had a profound cooling effect. The eruptions could have triggered a chain reaction, affecting sea ice and ocean currents in a way that lowered temperatures for centuries.â€
The popular memories of the â€˜Little Ice Ageâ€™ happen to be of the â€˜frost fairsâ€™ held on the ice of the River Thames in London and the destruction of towns by the advancing glaciers in mountain valleys. These effects were not viewed as any â€˜Ice Ageâ€™ by communities other than geological scientists, and were more popularly known for the literature of Chaucer and the age preceding the famous Tudors of England. But the team of scientists who reached this conclusion claim these had its origins much before Chaucer wrote his first sonnet.
Gifford Miller, lead author of the University of Colorado Boulder, said, â€œThe dominant way scientists have defined the Little Ice Age is by the expansion of big valley glaciers in the Alps and in Norway. But the time in which European glaciers advanced far enough to demolish villages would have been long after the onset of the cold period.â€
The team religiously radiocarbon-dated more than 150 samples collected from beneath receding margins of ice caps on Baffin Island in the Canadian Arctic. These samples happened to be of dead plant material with roots intact, They discovered that a large number of death-dates of these plant happen to fall between 1275 and 1300 AD. This was a clear indication of the planst being engulfed by ice during a relatively sudden event â€“ the Little Ice Age!
They also found another duration when there seemed to be mass death of plants â€“ around 1450 AD. After finding the second death date, the group decided to broaden the search and started analyzing sediment cores from a glacial lake linked to the 367-square-mile LangjÃ¶kull icecap in the central highlands of Iceland in hope of catching some other clues.
The scientists then found that during the 13th and 15th centuries the annual layers in the cores suddenly became thicker due to increased erosion caused by the expansion of the ice cap as the climate cooled. These could be relatively reliably dated by using tephra deposits from known historic volcanic eruptions on Iceland going back more than 1,000 years.
Miller added, â€œThat showed us the signal we got from Baffin Island was not just a local signal, it was a North Atlantic signal. This gave us a great deal more confidence that there was a major perturbation to the Northern Hemisphere climate near the end of the 13th century.â€