Ice-sheet collapse and sea-level rise at the Bølling warming 14,600 years ago

Past sea-level records provide invaluable information about the response of ice sheets to climate forcing. Some such records suggest that the last deglaciation was punctuated by a dramatic period of sea-level rise, of about 20 metres, in less than 500 years. Controversy about the amplitude and timing of this meltwater pulse (MWP-1A) has, however, led to uncertainty about the source of the melt water and its temporal and causal relationships with the abrupt climate changes of the deglaciation. Here we show that MWP-1A started no earlier than 14,650 years ago and ended before 14,310 years ago, making it coeval with the Bølling warming. Our results, based on corals drilled offshore from Tahiti during Integrated Ocean Drilling Project Expedition 310, reveal that the increase in sea level at Tahiti was between 12 and 22 metres, with a most probable value between 14 and 18 metres, establishing a significant meltwater contribution from the Southern Hemisphere. This implies that the rate of eustatic sea-level rise exceeded 40 millimetres per year during MWP-1A. An international drilling programme that explored offshore from the Tahiti reef establishes that an episode of rapid sea-level rise, meltwater pulse 1A, occurred between 14,650 and 14,310 years ago, and that the rise in sea level was probably between 14 and 18 metres. Antarctic ice-sheet collapse and sea-level changes A rapid sea-level rise occurred towards the end of the last ice age, during an event known as meltwater pulse 1A. The precise magnitude and timing of the event have remained obscure, rendering the climate forcings and consequent ice-sheet responses unclear. Pierre Deschamps and colleagues now report the results of a major coral-drilling programme in Tahiti, and establish that meltwater pulse 1A took place between 14,650 and 14,310 years ago, coincident with a warming spike. Sea levels rose by between 14 and 18 metres. Such a large rise suggests that ice-sheet collapse in Antarctica may have contributed to these changes, previously a point of much contention.