Sea level fingerprinting of the Bering Strait flooding history detects the source of the Younger Dryas climate event

Abstract

During the Last Glacial Maximum, expansive continental ice sheets lowered globally averaged sea level ~130 m, exposing a land bridge at the Bering Strait. During the subsequent deglaciation, sea level rose rapidly and ultimately flooded the Bering Strait, linking the Arctic and Pacific Oceans. Observational records of the Bering Strait flooding have suggested two apparently contradictory scenarios for the timing of the reconnection. We reconcile these enigmatic datasets using gravitationally self-consistent sea-level simulations that vary the timing and geometry of ice retreat between the Laurentide and Cordilleran Ice Sheets to the southwest of the Bering Strait to fit observations of a two-phased flooding history. Assuming the datasets are robust, we demonstrate that their reconciliation requires a substantial melting of the Cordilleran and western Laurentide Ice Sheet from 13,000 to 11,500 years ago. This timing provides a freshwater source for the widely debated Younger Dryas cold episode (12,900 to 11,700 years ago).

The role of Northeast Pacific meltwater events in deglacial climate change

“…While the timing of major meltwater events from the Cordilleran and Laurentide ice sheets appears to have been somewhat asynchronous during the early deglaciation, cooling during the YD was generally synchronous and of similar magnitude between sites in the Northeast Pacific and midlatitude North Atlantic, pointing to essentially synchronous meltwater influences in both ocean basins in this abrupt Northern Hemisphere cooling event. While dates for the submergence of the Bering Strait remain controversial, our results suggest that if the strait was breached at the beginning of the YD (30,32), then some of the meltwater funneled into the Northeast Pacific may have been transported through the Arctic and into North Atlantic deepwater formation regions. Thus, major meltwater pulses to the Northeast Pacific and attendant impacts on ocean circulation and sea-ice formation may have played a hitherto underrepresented role in abrupt deglacial climate variability.…”

Deglacial to Holocene variability in surface water characteristics and major floods in the Beaufort Sea

“…Additionally, the total inundation of the Bering Strait occurred at ca. 11 kyr BP and the Pacific Water inflow may have contributed warm water to this site 45 . In the mid-late Holocene (8-0 kyr BP), RI-OH′-SST values were quite low and stable ( Fig.…”

“…geochemical, and geophysical data) from sediment cores suggest an initial opening of Bering Strait at about 11.5 kyr BP 46,62,63 , whereas other evidence based on marine species dispersal suggests an earlier connection at about 13.3 kyr BP [64][65][66] . These contradictory evidences are recently reconciled by a gravitationally self-consistent sea-level simulation 45 . The authors predict the first opening of Bering Strait with shallow inundation at ca.…”

“…6c). This may be explained by the fact that the Beaufort Sea itself is an oligotrophic system 6 , and the Bering Strait was still closed at that time (>13 kyr BP), hence preventing the inflow of nutrient-rich Pacific Water 45,46 . Primary productivity shortly increased during the early YD (Figs.…”

“…11 kyr BP as well as subsequent moderate increases during the early Holocene ( Fig. 7e), possibly caused by high terrigenous input (including nutrients) and the total inundation of Bering Strait, respectively 45 . Furthermore, maximum summer insolation 47 may have caused shorter sea-ice seasons at the core site.…”