Terrigenous Sedimentation on the Submarine Shirshov Ridge (Bering Sea) during the Last Deglaciation

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-XRF data and sediment facies analysis of laminae reveals an alternation between predominantly terrigenous and diatom-dominated opal sedimentation. The diatomaceous laminae are interpreted to represent spring/summer productivity events that occur at the retreating sea ice margin. We identified five laminated sections in the deglacial part of our site. Laminae counts were carried out on these sections and correlated to the Bølling–Allerød and Preboreal phases in North Greenland Ice Core (NGRIP) oxygen isotope record, indicating an annual deposition of individual laminae couplets. The observed rapid intra-decadal intensifications of anoxia, in particular within the Bølling–Allerød, are tightly coupled to short-term warm events through increases in regional biogenic productivity. By correlating the counted laminated sections with Bering Sea Surface Temperature records (SST) and NGRIP δ18O data, we propose a deglacial minimum SST of 6–7 °C for the preservation of laminae, which we call the deglacial temperature threshold for anoxia occurrence, a process that strongly implies a close atmospheric teleconnection between the North Pacific and North Atlantic regions. We suggest that concomitant increases in Bering Sea biogenic productivity, 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 to determine calendar age control points for the Bølling–Allerød and the Preboreal that are independent of the initial radiocarbon-based chronology. Resulting calculated reservoir ages are 875 yr during the Bølling–Allerød, and 910–770 yr for the Younger Dryas and the Preboreal, respectively.

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High organic carbon deposition in the northern margin of the Aleutian Basin (Bering Sea) before the last deglaciation

Ocean Science Journal ◽

10.1007/s12601-010-0019-y ◽

2010 ◽

Vol 45 (4) ◽

pp. 203-211 ◽

Cited By ~ 11

Author(s):

Boo-Keun Khim ◽

Sunghan Kim ◽

Masao Uchida ◽

Takuya Itaki

Keyword(s):

Organic Carbon ◽

Bering Sea ◽

Carbon Deposition ◽

Last Deglaciation ◽

Northern Margin ◽

The Last Deglaciation ◽

Aleutian Basin

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Terrigenous sedimentation on the submarine Shirshov Ridge (Bering Sea) during the last deglaciation

Литология и полезные ископаемые ◽

10.31857/s0024-497x20192102-118 ◽

2019 ◽

pp. 102-118

Author(s):

I. O. Murdmaa ◽

E. V. Dorokhova ◽

E. A. Ovsepyan ◽

O. M. Dara ◽

D. Nürnberg

Keyword(s):

Grain Size ◽

Sea Ice ◽

Bering Sea ◽

Younger Dryas ◽

Size Distributions ◽

Suspended Material ◽

Terrigenous Sedimentation ◽

Shirshov Ridge ◽

Grain Size Distributions ◽

Bottom Waters

The submarine Shirshov Ridge is an independent system of terrigenous sedimentation, which is geomorphologically isolated from bottom terrigenous influx into the deep-water basin of the Bering Sea. Using the ridge as example, we studied background hemipelagic sedimentation of the finely dispersed terrigenous suspended material from water column and deposition of the coarser grained ice-rafted material in the western part of the deep-water basin. The grain-size and mineral composition of postglacial sediments of the Shirshov Ridge was studied in cores SO201-2-85KL and SO201-2-77KL taken from local basins in the central and southern parts of the ridge, respectively. Statistic treatment of uninterrupted grain-size distributions (GD) of terrigenous component of the postglacial sediments by end-member (EM) modelling revealed that the grain-size distributions of terrigenous sediments from two cores are determined by the mixing of three EMs. EM-1 and EM-2 reflect the hemipelagic sedimentation with and without bottom currents influence respectively, while EM-3 with mode at fine-grained sand characterizes GD of the ice-rafted material. Reconstructed mechanisms of terrigenous influx on the Shirshov Ridge involve advection of the suspended matter with surface and intermediate water masses and ice-rafting. The relative role of both mechanisms of the terrigenous sedimentation under the influence of varying bottom current velocities for intervals of Last Glacial Maximum, early deglaciation, Heinrich event 1, Bølling–Allerød, Younger Dryas, and Early Holocene is estimated. It is ascertained that the grain-size distribution of terrigenous component is defined by climate variations, sea ice coverage, sea ice drift pathways, conditions of fast ice melting, and mobility of bottom waters. High concentrations of drifting ice or seasonal sea ice cover likely existed above the southern part of the ridge during the second half of the Heinrich 1 event. The low mobility of bottom waters facilitated only the subice hemipelagic sedimentation of fine fractions from the background reserve of suspended material. A sharp reduction of ice-rafted flux was reconstructed for the Bølling–Allerød warming interval. Bottom currents affected sedimentation in the central part of the ridge during the entire deglaciation (in addition to the second half of the Heinrich 1 event), and in the southern part during the Bølling–Allerød, Younger Dryas, and Early Holocene.

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Laminated sediments in the Bering Sea reveal atmospheric teleconnections to Greenland climate on millennial to decadal timescales during the last deglaciation

Climate of the Past ◽

10.5194/cp-10-2215-2014 ◽

2014 ◽

Vol 10 (6) ◽

pp. 2215-2236 ◽

Cited By ~ 13

Author(s):

H. Kuehn ◽

L. Lembke-Jene ◽

R. Gersonde ◽

O. Esper ◽

F. Lamy ◽

...

Keyword(s):

Bering Sea ◽

North Pacific ◽

North Pacific Ocean ◽

Gulf Of Alaska ◽

Laminated Sediments ◽

Last Deglaciation ◽

Export Production ◽

Decadal Scale ◽

The Last Deglaciation ◽

The Bering Sea

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.

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