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Paleocene-Eocene Thermal Maximum to Eocene-Oligocene Cooling | GEO GIRL

Climate in the Paleogene went from a sharp warming event, the Paleocene Eocene Thermal Maximum (PETM), to a more long term warming, the Early Eocene Optimum (EEO), to long term global cooling that continues today, the Eocene Oligocene Ice Age, which marks the beginning of the modern ice age, at least in the south pole region. The PETM was a sudden intense heating due to the powerful greenhouse gas effect of methane that was being released from melting methane hydrates at the time. This triggered a positive feedback mechanism because more warming caused more melting leading to higher methane concentrations and further warming. Warming at the poles decreased ocean mixing and circulation because warmer waters at the poles weren't sinking to drive thermohaline circulation, and tihs also weakened the temperature gradient between the equator and poles, which decreased wind speeds and upwelling at ocean margins, exacerbating the stagnat oceans and causing ocean anoxia. Eventually the methane was converted into CO2 which lengthened the warming event into the early Eocene epoch. Life during the PETM and early Eocene Optimum was adapted to these warm conditions even at high latitudes. The following cooling event caused mass extinction among these warm adapted species. Cooling started in the middle to late Eocene, then worsened at the Eocene-Oligocene Cooling (start of Ice Age that continues today). The cooling was due to tectonics in the south pole. Antarctica became isolated due to Austrailia's movement away from it and the opening of the Drake Passage between South America and Antarctica. This allowed cooling of Antarctic waters, glaciation of the continent, and sinking of cold waters around the south pole which led to thermohaline circulation of the ocean which re-oxygenation the previously warm, anoxic, and stagnant ocean of the Eocene. Methane hydrates were forming instead of melting at this point and C burial rates increased with primary productivity which were both positive feedbacks that further cooled the planet. Terrestrial vegetation went from tropical forests to dry woodlands & vast grasslands, which mammals had to adapt to. This cooling event put Earth into it's modern climate and environmental regime. References: Earth System History: https://amzn.to/3v1Iy0G GEO GIRL Website: https://www.geogirlscience.com/ (visit my website to see all my courses, shop merch, learn more about me, and donate to support the channel if you'd like!) Studying for an exam? Schedule Tutoring with me: https://GEOGIRLTutoring.as.me/ Hey there, Earth enthusiast! Check my favorite Earth-friendly products: Bamboo paper towels: https://shrsl.com/3cvkw Eco-Friendly Tote (great for grocery shopping!): https://shrsl.com/3cwfp Reusable straws + cleaning brushes (my fav!): https://shrsl.com/3cwft Eco-friendly laundry detergent: https://shrsl.com/3cwgo Directly offset your carbon footprint with Wren: https://shrsl.com/3d0t2 Non-textbook books I recommend: Oxygen by D. Canfield: https://amzn.to/3gffbCL Brief history of Earth by A. Knoll: https://amzn.to/3w3hC1I Life on young planet by A. Knoll: https://amzn.to/2RBMpny Some assembly required by N. Shubin: https://amzn.to/3w1Ezm2 Your inner fish by N. Shubin: https://amzn.to/3cpw3Wb Oxygen by N. Lane: https://amzn.to/3z4FgwZ Alien Oceans by K. Hand: https://amzn.to/3clMx1l Life's Engines: https://amzn.to/3w1Nhke Tools I use as a geologist/teacher/student: Geology field notebook: https://amzn.to/3lb6dJf Geology rock hammer: https://amzn.to/3DZw8MA Geological compass: https://amzn.to/3hfbdLu Geological hand lens: https://amzn.to/3jXysM5 Camera: https://amzn.to/3l6fGRT Carbon-neutral pencil bag: https://shrsl.com/3cvjv Carbon-neutral backpack: https://shrsl.com/3cvkc 0:00 When was the Paleogene? 0:38 Climate trends in the Paleogene 2:01 Paleocene Eocene Thermal Maximum (PETM) 3:22 Role of greenhouse gases in PETM 5:12 Role of warm poles in PETM 6:41 Early Eocene Warming (EEO) 8:22 Warm poles continued to weaken T gradients 10:10 How life was affected by PETM & EEO 10:35 Cooling in the middle to late Eocene 12:37 Eocene-Oligocene Cooling (start of Ice Age!) 13:37 Beginning of modern ocean circulation 14:47 Isolation of Antarctica caused cooling? 15:57 C sinks accentuated cooling 17:09 Mass extinctions due to global cooling 18:01 Tropical forests became dry woodlands & grasslands 19:20 Mammal changes in new environment 20:02 This cooling event changed Earth forever! Disclaimer: Links included in this description might be affiliate links. If you purchase a product or service with the links that I provide I may receive a small commission, but there is no additional charge to you! Thank you for supporting my channel so I can continue to provide you with free content each week! And as always, let me know your topic suggestions in the comments down below!