A 200,000 year heatwave
Drill cores extracted from the rock of Spitsbergen contain a detailed record of a dramatic, ancient climate shift. Around 56 million years ago, at the boundary between the Paleocene and Eocene epochs, Earth experienced the most rapid period of natural global warming known in the geological record. This event is called the Paleocene-Eocene Thermal Maximum, or PETM. Over a period of about 200,000 years, global average temperatures rose by 5 to 8°C (9 to 14°F).
The warming was driven by the release of thousands of gigatons of carbon into the ocean and atmosphere. Geochemical analysis of sediment layers in Svalbard and elsewhere points to massive volcanic activity in the North Atlantic as a likely trigger. This initial warming may have then melted frozen methane deposits on the seafloor, releasing even more greenhouse gases. The evidence for this immense carbon injection is found globally in a feature called a carbon isotope excursion—a distinct shift in the ratio of carbon isotopes in ancient sediments. The PETM section of the Svalbard drill cores, found in the Frysjaodden Formation, clearly shows this isotopic signature. It also reveals an increase in kaolinite clay, a mineral that indicates intense chemical weathering on land due to higher temperatures and heavy rainfall.