Environmental precursors to rapid light carbon injection at the Palaeocene/Eocene boundary

Early warming signs The Palaeocene/Eocene thermal maximum — a period of intense global warming about 55 million years ago — was associated with a massive release of isotopically distinctive greenhouse gases into the ocean-atmosphere system. It remains unclear, however, whether this input caused or resulted from the global warming and environmental change that characterize the event. Sluijs et al . use high-resolution records of environmental change across the Palaeocene/Eocene boundary from two sediment sections in New Jersey to shed light on this question. They find that the onset of environmental change and surface-ocean warming preceded the input of greenhouse gases by several thousand years at this location. This sequence of events is consistent with the proposal that deep-ocean warming caused the dissociation of submarine gas hydrates, releasing massive amounts of the greenhouse gas methane. But the cause of the early warming remains uncertain. Exceptionally high resolution records of environmental change across the Palaeocene/Eocene boundary from two sediment sections in New Jersey find that the onset of environmental change and surface–ocean warming preceded the input of greenhouse gases by several thousand years. This sequence is consistent with the proposal that warming of the deep ocean caused the dissociation of submarine gas hydrates, which released massive amounts of methane. The start of the Palaeocene/Eocene thermal maximum—a period of exceptional global warming about 55 million years ago—is marked by a prominent negative carbon isotope excursion that reflects a massive input of 13 C-depleted (‘light’) carbon to the ocean–atmosphere system 1 . It is often assumed 2 that this carbon injection initiated the rapid increase in global surface temperatures and environmental change that characterize the climate perturbation 3 , 4 , 5 , 6 , 7 , but the exact sequence of events remains uncertain. Here we present chemical and biotic records of environmental change across the Palaeocene/Eocene boundary from two sediment sections in New Jersey that have high sediment accumulation rates. We show that the onsets of environmental change (as recorded by the abundant occurrence (‘acme’) of the dinoflagellate cyst Apectodinium ) and of surface-ocean warming (as evidenced by the palaeothermometer TEX 86 ) preceded the light carbon injection by several thousand years. The onset of the Apectodinium acme also precedes the carbon isotope excursion in sections from