Reconstruction of ice conditions in the northern Chukchi Sea during recent centuries: Geochemical proxy compared with observed data

Production of Ancient Dissolved Organic Carbon in Arctic Ocean Sediment: A Pathway of Carbon Cycling in the Extreme Environment

“…If we examined the solid phase δ 13 C‐TOC values alone in the surface sediments, there was a narrow range of δ 13 C (−22.1‰ to −23.1‰) for TOC. This result could suggest the deposition of a large fraction of marine‐derived OM on the inner shelf and slope region of the Arctic Ocean in past decades, as reported recently (Astakhov et al, ; Morris et al, ). The rapid degradation of the newly deposited OC could have resulted in the accumulation of more refractory terrestrial TOC preserved at depth in the sediments.…”

“…However, the distinct shift in TOC and HC Δ 14 C values from the shelf to slope in the surface sediments (Figure 2) cannot be explained by the deposition and degradation of marine-and terrestrial-derived OM alone. At the very surface (0-2 cm), sediments were deposited over approximately 25 years on the shelf and 50 years on the slope; these estimates were based on the sedimentation rates measured for the Chukchi Sea shelf (0.84 mm year -1 ) and the slope region (≤0.60 mm year −1 ) (Astakhov et al, 2019;Yu et al, 2012). The TOC 14 C ages at 0-2 cm were 4,430, 5,850 and 6,860 years for Cores R09, R11 and R14, respectively.…”

Composition of recent bottom sediments of the Chukchi Sea. Results of an integrated sedimentological research

“…The composition of surface sediments of the Chukchi Sea reflects considerable changes in the natural environment during the recent, warmer decades and differs distinctly from the cooler conditions during LIA. They are caused by an increase of the inflow of warm Pacific waters through the Bering Strait (Woodgate, 2018), a decrease in arctic ice cover (Astakhov et al, 2019) and a change in the redox conditions of bottom waters after 1980 (Bunzel et al, 2016). In summary this leads to an increase of bioproductivity within the water and higher concentrations of biogenic elements in the uppermost sediment layers of the Chukchi Sea.…”

“…They were described by smear slides and analyzed for magnetic susceptibility (MS), grain size, biogenic silica (SiO 2bio ), organic carbon (C org ), total nitrogen (N tot ), diatom and palynological analyzes. Dating of cores was carried out by 210 Pb and 137 Cs measurements (Astakhov et al, 2019; Vologina et al, 2019).…”

“…Older sediments have been determined within the northern part of the Chukchi Sea (core b16), where sediments of the Little Ice Age (LIA) were detected. They show very low concentrations of SiO 2bio , C org , N tot and concurrently high contents of the coldwater diatom species Thalassiosira antarctica (Astakhov et al, 2019;Vologina et al, 2019).…”