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

Abstract

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.

Pronounced interannual variability in tropical South Pacific temperatures during Heinrich Stadial 1

“…The HS1 coral lived in a water depth of ≤10 m, more likely in ≤5 m (ref. 18), similar to our modern Tahiti corals. Consequently, less variance at ENSO periods relative to today in the HS1 coral δ 18 O record can be interpreted as a change in the influence of the SPCZ and/or the salinity front on Tahiti δ 18 O seawater during HS1.…”

“…Powder X-ray diffraction, petrographic thin sections, scanning electron microscopy (SEM) and micronscale laser ablation (LA)-ICP-MS analyses indicate that the aragonitic coral skeleton is well preserved (Supplementary Methods and Supplementary Figs S1-S7). Two highly consistent U-Th ages indicate that the coral grew 14.994 ± 0.025 thousand years before the present (kyr BP; 'present' is defined as AD 1950) 18 (see Methods and Supplementary Table S1), a few centuries before the onset of the Bølling warming at 14.642 kyr BP (maximum counting error 0.186 kyr) 19 that followed the cold HS1 in the North Atlantic (Fig. 2).…”

“…U-Th analyses were performed using a VG-54 thermo-ionization mass spectrometer equipped with a 30-cm electrostatic analyser and a pulsecounting Daly detector at CEREGE 18,51 mean value of 1.1453 ± 0.0009 (2σ). This value is within the larger range adopted by the IntCal Group 52 as isotopic screening criterion in the 0-17 kyr interval (( 234 U/ 238 U) 0 = 1.1452 ± 0.0048, 2σ), as a necessary condition for closed system behaviour of U-series isotopes 52 (Supplementary Table S1 26,57 .…”

Abrupt Bølling warming and ice saddle collapse contributions to the Meltwater Pulse 1a rapid sea level rise

“…In total, this produced around 130 m of global mean sea level rise (GMSLR) [ Lambeck et al ., 2014], which was sometimes contributed to by major episodes of accelerated ice melt. Meltwater Pulse 1a (MWP1a) is the largest of these, identified as a 14–18 m of GMSLR in less than 340 years at 14.6 ka [ Deschamps et al ., 2012] in coral reef records from Tahiti and Barbados, as well as other sea level proxies around the world. This event also occurred around the time of an abrupt Northern Hemisphere warming of 4–5°C that took place within a few decades to centuries [ Buizert et al ., 2014; Deschamps et al ., 2012].…”

“…Meltwater Pulse 1a (MWP1a) is the largest of these, identified as a 14–18 m of GMSLR in less than 340 years at 14.6 ka [ Deschamps et al ., 2012] in coral reef records from Tahiti and Barbados, as well as other sea level proxies around the world. This event also occurred around the time of an abrupt Northern Hemisphere warming of 4–5°C that took place within a few decades to centuries [ Buizert et al ., 2014; Deschamps et al ., 2012]. However, the link between this intense ice melt and warming remains elusive.…”