Reconstructing ice conditions in the southern Chukchi Sea during the last millennium based on chemical composition of sediments and diatom assemblages

Climate and ice conditions of East Siberian Sea during Holocene: Reconstructions based on sedimentary geochemical multiproxy

“…- Create multiple timescale geochemical series of the LV77-36-2 core for normalized elements in rubidium (Figure 2) and normalized minimax (Astakhov et al, 2020); then, smooth them for 10-year intervals, transforming the time scale into a yearly integer-timescale geochemical series.…”

“…Reconstruction of ice extent (d, e, f, g, h) and anomalies of air temperature at the surface (a–c) for the Middle and Late Holocene in the Arctic, based on the results of the study of cores LV77-36-1 and LV77-36-2 (c and d) and other sources. (a) reconstruction of air temperature anomalies on the surface (SAT) (Marcott et al, 2013); (b) pollen-based reconstruction of summer air temperatures (SAS) of lake Dolgoe (Lena River Delta) (Klemm et al, 2013); (c) anomalies of average annual air temperature (ΔT 10 ): results of observations (red line) and reconstruction on cores LV77-36-2 (green line) and LV77-36-1 (blue thin and blue bold (9 – point running average) lines); (d) duration of ice-free period at station LV77-36 based on observations (red line) and reconstruction on cores LV77-36-1 (blue and purple [9 – point running average] lines) and LV77-36-2 (green line); (e) the linearity-detrended IP 25 record (green) and the band-pass filtered 1800 years cycle (red) in core PS51/159 from Laptev Sea (Hörner et al, 2016); (f) biomarker PIP 25 values for core PS72/350 from East Siberian Sea and ARA2B-1A from Chukchi Sea (Stein et al, 2017); (g) reconstruction of ice-free period duration (IF 10 ) on core LV77-3 from Chukchi Sea (Astakhov et al, 2020); (h) reconstruction of Arctic ice cover for the last 1450 years (Kinnard et al, 2011). The yellow fill highlights the periods of increased ice coverage (cold stages of the 1800-year Bond cycles) of the Laptev Sea (Hörner et al, 2016).…”

“…At the station LV77-3 from the southern part of the Chukchi Sea, biogenic elements were not included in the transfer functions, which is explained by the location of the station near the Bering Strait. Variations in bioproductivity here are determined by the changes of the temperature and volume of Pacific waters entering through the strait, and not by the ice coverage (Astakhov et al, 2020).…”

“…The upper 150 cm of the core (5.5 ka) was characterized by a low sedimentation rate (Dong et al, 2022) and analyzed with a step of 1 cm; however, the lower 150 cm of the core exhibited a step of 2 cm. Other sediment characteristics (grain size, TOC, and opal), total diatom content, and diatom assemblages were studied using a method in the literature (Astakhov et al, 2020; Tsoy et al, 2017) with a step of 2–4 cm.…”

“…The method of "transfer functions" was used by the authors of this article to reconstruct the duration of the ice-free period (IF 10 ) and anomalies of the mean annual air temperature (∆T 10 ) over the past centuries and millennia at several stations in the Chukchi Sea (Astakhov et al, 2019a(Astakhov et al, , 2020. Transfer functions were developed by comparing the time series of the chemical composition of the bottom sediments accumulated over the observation period with the hydrometeorological data.…”