Post-glacial flooding of the Bering Land Bridge dated to 11 cal ka BP based on new geophysical and sediment records

Martin Jakobsson,Jan Backman,Larry A Mayer,Thomas M Cronin,Johan Nilsson,Igor Semiletov,Christof Pearce,Christian Stranne,Göran Björk,Agatha De Boer,Helen Coxall,Leif G Anderson,Jayne E Rattray,Carl-Magnus Mörth,Matt O'Regan,Natalia Barrientos

doi:10.5194/cp-13-991-2017

Abstract

Abstract. The Bering Strait connects the Arctic and Pacific oceans and separates the North American and Asian landmasses. The presently shallow ( ∼ 53 m) strait was exposed during the sea level lowstand of the last glacial period, which permitted human migration across a land bridge today referred to as the Bering Land Bridge. Proxy studies (stable isotope composition of foraminifera, whale migration into the Arctic Ocean, mollusc and insect fossils and paleobotanical data) have suggested a range of ages for the Bering Strait reopening, mainly falling within the Younger Dryas stadial (12.9–11.7 cal ka BP). Here we provide new information on the deglacial and post-glacial evolution of the Arctic–Pacific connection through the Bering Strait based on analyses of geological and geophysical data from Herald Canyon, located north of the Bering Strait on the Chukchi Sea shelf region in the western Arctic Ocean. Our results suggest an initial opening at about 11 cal ka BP in the earliest Holocene, which is later than in several previous studies. Our key evidence is based on a well-dated core from Herald Canyon, in which a shift from a near-shore environment to a Pacific-influenced open marine setting at around 11 cal ka BP is observed. The shift corresponds to meltwater pulse 1b (MWP1b) and is interpreted to signify relatively rapid breaching of the Bering Strait and the submergence of the large Bering Land Bridge. Although the precise rates of sea level rise cannot be quantified, our new results suggest that the late deglacial sea level rise was rapid and occurred after the end of the Younger Dryas stadial.

Highlights

The ∼ 85 km wide and ∼ 53 m deep Bering Strait forms a Pacific–Arctic connection that influences Arctic Ocean circulation, surface water composition, nutrient flux, sea ice and marine ecosystems (Grebmeier, 2011; Watanabe and Hasumi, 2009)
Herald Canyon topographically steers the western branch of Pacific water flowing into the Arctic Ocean (Pickart et al, 2010; Woodgate and Aagaard, 2005), implying that cores 2PC1 and 4-PC1 are strategically placed to record this critical component of Arctic Ocean paleoceanography
Evidence of pre-Clovis cultures that made it into North and South America and the likelihood that they traveled by boat across the Bering Strait have toned down the significance of a Bering Land Bridge for human migration pathways (Erlandson et al, 2007)

Summary

Introduction

The ∼ 85 km wide and ∼ 53 m deep Bering Strait forms a Pacific–Arctic connection that influences Arctic Ocean circulation, surface water composition, nutrient flux, sea ice and marine ecosystems (Grebmeier, 2011; Watanabe and Hasumi, 2009). The throughflow was initially proposed to be primarily driven by the mean sea level difference between the Pacific (higher) and the Arctic Ocean (lower; Stigebrandt, 1984), later work has pointed to the importance of both the farfield wind stress (De Boer and Nof, 2004a, b; Ortiz et al, 2012) and the near-field wind stress (Aagaard et al, 2006; Danielson et al, 2014). Jakobsson et al.: Post-glacial flooding of the Bering Land Bridge dampen abrupt climate transitions, thereby emphasizing the critical role of a Pacific–Arctic connection in Earth’s climate system (De Boer and Nof, 2004b; Hu et al, 2012, 2015; Sandal and Nof, 2008)

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Conclusion