One of the largest scorching deserts in the world, the Sahara desert has an area of around 9,200,000 square kilometres presently. But throughout the centuries, this arid land occasionally became lush with savannahs, rivers, lakes, and creatures that needed water, like hippos. When and how these “green phases” occurred are revealed by a recent scientific investigation.
The scientific study, which was released on Friday in the journal Nature Communications, demonstrates how variations in Earth’s orbit around the Sun were responsible for the Sahara Desert’s recurring wet periods. During the cold ages, these wet episodes were likewise inhibited.
“The cyclic transformation of the Sahara Desert into savannah and woodland ecosystems is one of the most remarkable environmental changes on the planet. Our study is one of the first climate modelling studies to simulate the African Humid Periods with comparable magnitude to what the palaeo climate observations indicate, revealing why and when these events occurred,” mentioned the lead author Edward Armstrong, a climate scientist at the University of Helsinki and the University of Bristol during a press interaction.
These “greenings” may have been caused by modifications to Earth’s orbital precession, according to this new study. The term “precession” describes the tilt of the Earth’s axis. This affects seasonality throughout a period of around 21,000 years. This in turn regulates the intensity of the African Monsoon and the distribution of vegetation in the area.
The study confirmed that the North African humid periods occurred every 21,000 years, as predicted by variations in the planet’s orbital precession, using sophisticated climate models. The Northern Hemisphere saw warmer summers as a result of these changes, which strengthened the West African monsoon system. As a result of the Sahara’s increasing rainfall, savannah-like vegetation began to spread throughout the desert.
