Prior to 10,000 years ago, the Earth's climate was characterized by warm temperatures, which gave rise to early civilization. An analysis of ice taken from various sites in Greenland revealed that just before this warm period, the temperature varied irregularly from warm to cold for about 1,000 years. The average winter temperature in northern Europe changed 10 degrees in a short ten years. The last cold period, called the "Younger Dryas" time, ended about 11,000 years ago. Evidence of this phenomenon can be seen in the accumulations in the North Atlantic Ocean and ice from the Scandinavian peninsula and Iceland. Evidence can also be found in swamps and lakes of Northern Europe and the coastal areas of Canada, demonstrating that this was a global phenomenon.
There is no clear explanation of the cause of this sudden change in climate, though a few hypotheses have been presented. Research using the present weather model has shown that the circulation of temperature and salt determines the density of ocean water. This is called the ocean thermal salt circulation. This circulation changes suddenly accompanying changes in the Earth's climate. In the coastal area of Northern Europe, the climate is warm and moderate due to the influence of warm surface water circulation. However, the mixing of cold pure water can quickly disrupt this circulation and cause sudden drops in temperature. It is now evident that this mixing of cold water has occurred at least eight times. Analysis of the accumulation in the Northern Atlantic determined that the source of the cold water was the melting of huge icebergs originating in Canada. Unfortunately, we do not yet know the cause of the melting. However, several possibilities can be considered. ! For example, the global ocean circulation and atmospheric temperature variations may have interacted to cause global environmental changes.