Core Insights - The research published in the journal "Nature Geoscience" reveals that changes in ocean sulfate concentrations can alter methane consumption methods, shedding light on the carbon cycle mechanisms behind the extreme global warming and ocean acidification during the Paleocene-Eocene Thermal Maximum (PETM) 56 million years ago [1] Group 1: Methane Consumption and Carbon Cycle - Approximately 90% of methane in modern oceans is utilized by microorganisms in sediments under anoxic conditions, producing alkaline substances that mitigate ocean acidification [1] - During the PETM, the sulfate concentration in Arctic seawater was less than one-third of modern levels, leading to a shift where oxygen-loving bacteria began to "rapidly burn" methane, directly consuming oxygen and releasing carbon dioxide [1] - The reconstruction of carbon dioxide concentrations based on molecular traces from marine phytoplankton indicates that during the PETM recovery period, Arctic ocean CO2 levels were 200-700 ppm higher than the global average, indicating a transition from CO2 absorption to emission [1] Group 2: Implications for Arctic's Role in Carbon Cycle - The reduction in seawater salinity and sulfate led to methane being decomposed solely through "rapid burning," resulting in significant carbon dioxide production [1] - This fundamentally altered the Arctic's role in the global carbon cycle, transforming it from a carbon sink to a greenhouse gas emission source [1]