The Late Paleocene Thermal Maximum

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About 55 million years ago, as the Paleocene was drawing to an end, there was a warming event of remarkable magnitude, speed, and importance. This event is known as the Late Paleocene Thermal Maximum (LPTM), and it has been a topic of intense and relevant academic interest ever since it was first described.

From Zachos et al. 2001. Benthic foraminiferal record from two sites in the south Atlantic and one in the western Pacific. The records were correlated with carbon isotopes.

The Late Paleocene Thermal Maximum was a massive event with repercussions for the climate, oceans, and biota of Earth. Global temperatures increased by more than 5°C in less than 10 ky, with an even more pronounced change poleward. Evidence suggests that the atmospheric circulation weakened substantially. The changes in the ocean were similarly drastic: seafloor temperatures increased 4°C as the vertical temperature gradient all but vanished for more than 30,000 years. The calcium compensation depth shoaled nearly 2 kilometers in less than 1,000 years, as carbonate accumulation all but disappeared. Finally, the LPTM caused a mass extinction among benthic foraminifera and a global migration and radiation of mammals. (Adapted from Pagani et al, 2006)

The excursion in the carbon isotope record leaves very little doubt that a big flux of carbon dioxide was part of the LPTM, and that this CO₂ at least partially originated from the disassociation of an immense quantity of methane hydrate. However, the overall chain of events, and the causes of those events, remains to an exciting extent a mystery. Discovering the root cause, the “trigger,” of the LPTM would give us a much fuller understanding of this event and would help to illuminate paleoclimate in general. Furthermore, a fuller grasp on the causes and chronology of the LPTM would give us an invaluable chance to learn from a carbon influx of a similar magnitude and abruptness to the one we are creating today.