Palm trees, alligators, and warm weather might conjure thoughts of the tropics, but for a period during Earth’s history, all of these things could be found in polar regions! Today the Arctic and Antarctic are frozen landscapes, but millions of years ago the climate of these regions more closely resembled modern California or Florida!
Earth has undergone several major climatic shifts, oscillating between “hothouse” or “icehouse” states over millions of years. During “hothouse” conditions, Earth has no major ice sheets, atmospheric concentrations of greenhouse gasses like carbon dioxide are high, and temperature gradients between the tropics and polar regions are small. During icehouse periods, Earth’s climate is cooler, with large ice sheets and periods of glacial growth and retreat.
The Cenozoic Era began 66 million years ago, and continues to the present. In the early Cenozoic Era, Earth was in a hothouse phase; temperatures at the tropics were around 40 C (110 F), and 20 C (70 F) at the poles. During the Cenozoic Era, Earth began to cool, entering a period known as the Pleistocene Icehouse roughly 2.5 million years ago. The Pleistocene is typically what is referred to as an “Ice Age”; glaciers formed and temperature gradients between the poles were larger. Today, Earth is still in an icehouse stage.
Scientists seek to understand what drove the cooling trend during the Cenozoic Era to answer questions about our climate today, such as how warm temperatures were maintained in polar regions despite spending 6 months of the year in darkness, and what initiated the shift from hothouse to icehouse conditions using clues left behind millions of years ago.
This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links, please go to ocean.tamu.edu and click On the Ocean.
Featured image from: Mikkel Juul Jensen/SPL/Cosmos (left) and Aphelleon/Shutterstock (right)
Script Author: James M. Fiorendino
Contributing Professor: Dr. Yige Zhang