Abstract
Abstract. During the last glacial termination, the upper North Pacific Ocean underwent dramatic and rapid changes in oxygenation that lead to the transient intensification of oxygen minimum zones (OMZs), recorded by the widespread occurrence of laminated sediments on circum-Pacific continental margins. We present a new laminated sediment record from the mid-depth (1100 m) northern Bering Sea margin that provides insight into these deglacial OMZ maxima with exceptional, decadal-scale detail. Combined ultrahigh-resolution micro-X-ray-fluorescence (micro-XRF) data and sediment facies analysis of laminae reveal an alternation between predominantly terrigenous and diatom-dominated opal sedimentation. The diatomaceous laminae are interpreted to represent spring/summer productivity events related to the retreating sea ice margin. We identified five laminated sections in the deglacial part of our site. Lamina counts were carried out on these sections and correlated with the Bølling–Allerød and Preboreal phases in the North Greenland Ice Core (NGRIP) oxygen isotope record, indicating an annual deposition of individual lamina couplets (varves). The observed rapid decadal intensifications of anoxia, in particular within the Bølling–Allerød, are tightly coupled to short-term warm events through increases in regional export production. This dependence of laminae formation on warmer temperatures is underlined by a correlation with published Bering Sea sea surface temperature records and δ18O data of planktic foraminifera from the Gulf of Alaska. The rapidity of the observed changes strongly implies a close atmospheric teleconnection between North Pacific and North Atlantic regions. We suggest that concomitant increases in export production and subsequent remineralization of organic matter in the Bering Sea, in combination with oxygen-poor waters entering the Being Sea, drove down oxygen concentrations to values below 0.1 mL L−1 and caused laminae preservation. Calculated benthic–planktic ventilation ages show no significant variations throughout the last deglaciation, indicating that changes in formation rates or differing sources of North Pacific mid-depth waters are not prime candidates for strengthening the OMZ at our site. The age models established by our correlation procedure allow for the determination of calendar age control points for the Bølling–Allerød and the Preboreal that are independent of the initial radiocarbon-based chronology. Resulting surface reservoir ages range within 730–990 yr during the Bølling–Allerød, 800–1100 yr in the Younger Dryas, and 765–775 yr for the Preboreal.
Highlights
The last glacial termination is characterized by the widespread decrease of oxygen concentrations at mid-depth in the world ocean (Jaccard and Galbraith, 2012)
As it has further been suggested that higher primary production in the Chukchi Sea during the Holocene could result from the greater nutrient supply from the Bering Sea (e.g., Keigwin et al, 2006), we suggest the following mechanism: before 11 ka Bering Sea surface ocean circulation was substantially different from modern patterns, with an absent or weakened Anadyr Current and differing expression of the Bering Slope Current, leading to different interactions with the Alaskan Stream and the open North Pacific
Two laminated cores from the northern Bering Slope located in intermediate water depths allow for a tight coupling to Greenland ice core data on decadal timescales, especially for the deglacial Bølling–Allerød phase (GI-1, 14.64–12.85 ka)
Summary
The last glacial termination is characterized by the widespread decrease of oxygen concentrations at mid-depth in the world ocean (Jaccard and Galbraith, 2012). In the North Pacific, this prominent reduction led to the expansion of oxygen minimum zones (OMZs), culminating in the formation of anoxic, laminated sediment sequences at several continental margin locations (Fig. 1). H. Kuehn et al.: Laminated sediments in the Bering Sea reveal atmospheric teleconnections Sediment core. 179◦50.87 E 178◦53.99 E 179◦05.24 E 179◦05.24 E 177◦57.42 E 178◦49.45 E 179◦51.00 W 179◦27.95 W 179◦26.67 W 179◦26.61 W 175◦40.69 W 171◦04.95 W 170◦19.68 W 168◦48.66 W 168◦48.62 W 166◦59.32 E 169◦58.902 W 179◦31.297 W 179◦0.49992 E 176◦55.003 E 175◦48.966 W 179◦28.204 W 179◦26.508 W 168◦40.014 W 179◦27.82 W 179◦25.34 W 179◦27.78 W 179◦33.47 W 170◦13.38 W Depth (m b.s.l.)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
