During the history of Earth, the Arctic as a major ecological and climatic zone has to be seen as a rather untypical phenomenon: For billions of years, the climate was simply too warm for allowing such extensive cold regions even close to the poles. Also during our geological period, the Quarternary, the extent of the Arctic as an ecological zone depends highly on the changing prevailing climatic conditions: during the last ice ages, the Actic covered repeatedly major parts of the entire northern hemisphere, reaching in Europe all the way down into Spain. Then, its extent was much smaller than today during the climate optimum after the last ice age until about 5 000 years before present, the so-called Atlanticum. After that, the area increased and reached its maximum extent during the Little Ice Age about 300 - 150 years before present. Today, the Arctic as a climatic zone covers about 21 million square kilometers, with the Arctic Ocean as its center and at the same time its largest part (13 million square kilometres). This ocean is surrounded by an area of about 8 million square kilometers of arctic land masses (incl. islands), which include the north of Eurasia and America, as well as the mini continent Greenland. In total, these land areas equal about the extent of Australia. With the currently ongoing warming of climate, a gradual shrinking of the Arctic is a natural longterm consequence.