Roughly 700,000 years ago, the “Warm Ice Age” permanently altered Earth’s climate cycles. Coinciding with this exceptionally warm and wet period, the polar glaciers expanded dramatically. A European research team including geoscientists from the University of Heidelberg used recently obtained geological data in combination with computer simulations to pinpoint this seemingly paradoxical connection. According to the researchers, this profound change in the Earth’s climate was responsible for the change in climate cycles, and thus represents a crucial step in the subsequent climatic evolution of our planet.
Geological ice ages – called ice age periods – are characterized by the development of large ice sheets in the northern hemisphere. In the past 700,000 years, phases have shifted between distinct glacial and warm periods every 100,000 years. Before then, Earth’s climate was governed by 40,000-year cycles with shorter, weaker glacial periods. The change in climate cycles occurred in the Middle Pleistocene transition period, which began approximately 1.2 million years ago and ended about 670,000 years ago. “The mechanisms responsible for this critical change in the global climate rhythm are still largely unknown. They cannot be attributed to differences in the orbital parameters that govern the Earth’s climate,” explains Assistant Professor Dr. Andre Bahr of the Institute of Earth Sciences at the University of Heidelberg. “But the recently identified warm ice age, which caused the accumulation of continental ice excess, played a crucial role.”
In their investigations, the researchers used new climate records from core drilling off Portugal and loess records from the Chinese plateau. Then the data was entered into computer simulations. The models show a long-term trend of warming and wetting in both subtropical regions over the past 800,000 to 670,000 years. Concurrent with this last glacial period of the Middle Pleistocene transition, sea surface temperatures in the North Atlantic and tropical North Pacific were much warmer than in the preglacial period, the stage between the two ice ages. This has led to increased moisture production and precipitation in southwestern Europe, expansion of Mediterranean forests, and an increase in the summer monsoon in eastern Asia. Moisture has also reached the polar regions, where it has contributed to the expansion of the ice sheets in northern Eurasia. “They persisted for some time and ushered in a phase of continuous and far-reaching glaciation in the Pleistocene that lasted until the late Pleistocene. This expansion of continental glaciers was necessary to begin the transition from the 40,000-year cycles to the 100,000-year cycles we see today, which was crucial to the evolution of later Earth’s climate”, Andre Barr stated.
The results of this research have been published in the journal Nature Communications. Scientists from Germany, France, Spain and Portugal contributed to the research. The work was funded by the German Research Foundation.