The Late Cenozoic Ice Age is the third and current global ice age of the Phanerozoic eon. It began with the icing of Antarctica in the very end of the Eocene, around 34 million years ago, and also includes the shorter Quaternary glaciation, during which vast ice masses formed around the North Pole. Currently, this ice age continues as Greenland and Antarctica are still covered in ice. It is the only ice age of the Phanerozoic, during which extensive ice cover was formed not only in the southern, but also in the northern hemispheres.
From greenhouse to icehouse[]
Timeline of glaciations, shown in blue.
The previous glaciation, known as the Karoo ice age, ended in the Permian period, about 260 million years ago, and over the next ~226 million years, there were no permanent ice sheets on Earth. Such phases are called greenhouse, while the glacial periods are called icehouse in accordance with their climatic conditions. This last greenhouse interval spans the entire Mesozoic and therefore the period of all pterosaur and non-avian dinosaur existence. The reasons probably lie in the violent eruptions that accompanied the final formation and then the split of Pangea. In addition, from the Permian to the early Paleogene period, large land masses were absent from the poles. Even at the beginning of the Eocene, Ellesmere and Axel Heiberg islands of the Canadian High Arctic contained dense green forests consisting of elm, alder, birch and grapes.[1] However, at the end of the epoch, Antarctica began to be covered with permanent ice sheets.
Impact on climate and biota[]
Anthropornis, a large penguin that lived on Seymour Island off the coast of Antarctica at the beginning of the Late Cenozoic Ice Age
The new ice age had a strong impact on the biosphere. Antarctica, previously covered with forests and inhabited by a diverse fauna, became deserted. Currently, it is covered by the largest desert on the planet, where no land animals live. The freezing of polar waters led to changes in ocean currents and a cooling of the seas by ∼2.5 °C.[2] As a result of cooling, the climate became drier, which is noted, for example, in the Eocene-Oligocene deposits of southern Asia.[3] The beginning of the glaciation coincides with the Eocene–Oligocene extinction event. Many species poorly adapted to cold temperatures and dry climate went extinct. Among them were basilosaurid whales and multituberculates. At the same time, some animals managed to adapt to the colder weather. Penguins continued to live in the seas around Antarctica, with 5 species currently inhabiting the continent.
As cooling progressed, the climate became increasingly drier, and as a result, new ecosystems, savannas, arose in the Neogene. In this new environment, new forms of mammals emerged that are still widespread today. First of all, these are fleet-footed artiodactyls, such as antelopes and camels. Horses and elephants also evolved in savannas and steppes. At the end of the Miocene, as a result of forest reduction, bipedal primates appeared, adapted to life on the plains. From these primates, humans eventually descended.
During the Pleistocene, some animals in the northern hemisphere like woolly mammoths and woolly rhinoceroses adapted to the cold by acquiring warm fur.
2.58 million years ago, ice sheets began to form at the North Pole, marking the beginning of the Quaternary glaciation. The climate became even colder and drier, causing tropical forests to shrink and sea levels to drop as large volumes of water remained in the polar regions as ice. Adapting to the cold, some animals acquired a subcutaneous layer of fat, others acquired warm fur and fluff. The glaciers of the Northern Hemisphere have advanced and retreated many times, and during periods of warming, more heat-loving species have returned to high latitudes. The last glaciation in northern region ended 11,700 years ago, and the beginning of a new interglacial, which corresponds to the current Holocene epoch, is associated with this event.
Over the past 11,700 years, the climate has continued to change from warming to cooling (even minor ice ages are distinguished), but these fluctuations were relatively low compared to the Pleistocene glaciations. As the glaciers melted, the area of tropical forests began to increase again. However, large volumes of permanent ice remain in Antarctica and northern territories.
Future[]
At the time of the Meghalayan age and the Holocene epoch, the Earth is in an interglacial period. It is expected that the next stage of glaciation in the northern hemisphere may occur in 50,000 years. However, there is a possibility that global warming caused by human activity will weaken this cooling, or even make its onset impossible. In this case, after the melting of the ice masses in Greenland and Antarctica, the current ice age will end. On the other hand, there are models according to which Antarctica will remain near the south pole for millions of years, which will make the onset of new ice ages possible in the long term.
In popular culture[]
The second episode of Walking with Beasts takes place 36 million years ago, when the world was on the verge of a new ice age, and animals such as Basilosaurus and Embolotherium were already experiencing climate change.
References[]
- ↑ "Canadian High Arctic Islands Were Once Home to Rich Forests". https://www.sci.news/paleontology/paleocene-eocene-canadian-high-arctic-forests-07968.html.
- ↑ Lear, Caroline H.; Bailey, Trevor R.; Pearson, Paul N.; Coxall, Helen K.; Rosenthal, Yair (1 March 2008). "Cooling and ice growth across the Eocene-Oligocene transition". Geology. 36 (3): 251. DOI:10.1130/G24584A
- ↑ Li, Y. X.; Jiao, W. J.; Liu, Z. H.; Jin, J. H.; Wang, D. H.; He, Y. X.; Quan, C. (2016). "Terrestrial responses of low-latitude Asia to the Eocene–Oligocene climate transition revealed by integrated chronostratigraphy". Climate of the Past. 12 (2): 255–272. DOI:10.5194/cp-12-255-2016