The 14th century was a difficult time for Europe. Barely recovering from the plague epidemic, the survivors faced an abrupt climate change – the Little Ice Age. In just 20 years, the abnormally warm weather gave way to an icy cold. Today scientists have learned why this happened.
The Little Ice Age was one of the coldest periods in the last 10 thousand years. This cold snap has led to crop failures, hunger and pandemics, leading to the deaths of millions in Europe. Scientists at the University of Massachusetts at Amherst believe that the cold snap, which was especially felt in the North Atlantic region, was due to a previous unusually warm period, according to Phys.
Scientists François and Raymond Bradley created a 3,000-year-old reconstruction of the sea surface temperature in the North Atlantic and discovered an amazing feature. In the late 1300s, very warm conditions gave way to unprecedented cold conditions in the early 1400s which took only 20 years.
Scientists studied back in 2020 the annual layers of sediment in a lake in the north of Ellesmere Island, Canada, which contain titanium left over from centuries of weathering of rocks. By measuring the concentration of titanium in different layers, the scientists were able to estimate the change in temperature over time. It turned out that the lowest temperatures were recorded between 1400-1600 AD.
Researchers, as a result of new scientific work, discovered an abnormally strong transfer of warm water to the north in the late 1300s, which peaked around 1380. As a result, the waters south of Greenland are much warmer than usual.
Usually warm, salty water from the tropics flows northward along the coast of Northern Europe and when it reaches higher latitudes, it gives off its heat to the atmosphere, becomes colder (and therefore denser and heavier) and sinks to the ocean floor. The resulting deep-sea current then travels south along the coast of North America as part of a vast system of water circulation in the oceans.
But in the late 1300s, much more warm water was moving north than usual, which in turn led to the rapid loss of Arctic ice. Over the course of several decades in the late 1300s and early 1400s, vast amounts of breakaway ice entered the North Atlantic. Its melting has reduced the salinity of the ocean, disrupted water circulation and dramatically weakened the warm current that warms Europe. This is what caused a significant cooling, scientists say.
Interestingly, the reason for the warming, which eventually froze Europe, scientists call the increase in solar activity and the peculiarities of atmospheric circulation. The late 1300s saw unusually high solar activity, which intensified the warm current. Then there were fewer volcanic eruptions on Earth and there was less ash in the air. This “clean” atmosphere suggests that the planet was more susceptible to changes in solar activity.
“The impact of high solar activity on atmospheric circulation in the North Atlantic was particularly strong,” Lappoint said.
We need to keep a close eye on the accumulation of fresh water in the Beaufort Sea in northern Alaska. Over the past two decades, its fresh water content has increased by 40%. Exporting this water to the North Atlantic can greatly affect the circulation of ocean currents. In addition, over the past decade, periods of high atmospheric pressure have become more common in Greenland in summer.
Scientists note that a similar phenomenon – the slowing down of the Gulf Stream due to melting ice – is observed today. However, the scale of the cooling may be less, as there is very little Arctic sea ice left.