The Role of Ice Cover in the Formation of Bottom Sediment Chemical Composition on the East Siberian Shelf

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

“…Additionally, according to the distribution of PIP 25 in core ARA2B-1A (Figure 4f), IF 10 variations in core LV77-3 (Figure 4g), and variations in the area of ice cover in the Arctic as a whole (Figure 4h), periodicity and synchronism with climate change were not traced in ice cover reconstructions based on dinocysts in the cores from the northern part of the Chukchi Sea (de Vernal, 2017). Earlier reconstruction of IF 10 for the last century in the northern part of the Chukchi Sea (Astakhov et al, 2019a) and for core LV77-12 (Astakhov et al, 2021) from the southeastern part of the East Siberian Sea (Figure 1) revealed a lower ice cover in the Little Ice Age than that at the beginning of the 20th century, while demonstrating the absence of a correlation between climate (air temperature) and ice conditions. These features are determined by the existence of a predominant influence on the ice conditions of the Chukchi Sea and the adjacent water areas of the Pacific waters entering through the Bering Strait (Polyak et al, 2016; Stein et al, 2017; Woodgate et al, 2010).…”

“…Such a value of biogenic and redox-sensitive elements to the transfer functions is observed everywhere, but with some variations. The bromine is the main biogenic element in the formulas for the Chukchi and East Siberian Seas, and in the Laptev Sea, where the water is highly desalinated by the Lena River inflow, it replace by strontium (Astakhov et al, 2021). The accumulation of bromine in sediments strongly depends on water salinity (Mayer et al, 2007), so bioproductivity variations is lesser significant in its distribution in the Laptev Sea.…”

“…In the Laptev Sea at stations LV83-16 and LV83-32 (Figure 1), niobium and yttrium enter the IF 10 formulas with a positive sign (Astakhov et al, 2021), that is, their accumulation in sediments increases with a decrease in ice cover. Previously (Astakhov et al, 2021), it was explained by the proximity of these stations to the coasts, where the ice complex (yedoma) is intensively eroded (Figure 1). During the warming and a decrease of ice cover, the rate of coastal abrasion increases and silty material enriched with stable heavy minerals accumulated on the shelf.…”

“…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. The choice of chemical composition was determined by the technical possibility of its determination, with the required discreteness (fractions of a millimeter) and accuracy (Astakhov et al, 2021). Currently, this method is the only method that allows SAT reconstruction in marine areas.…”

“…Information on the duration of the ice-free period was obtained from the electronic climatic oceanographic atlas of the Arctic Ocean (Tanis and Timokhov, 1997, 1998) and from the website www.natice.noaa.gov/products/miz.html. This data were used for recorded the average ice edge for 10-day periods (decades) (Astakhov et al, 2021; Plotnikov and Pustoshnova, 2012). The main climatic parameter of the reconstruction was the variation in the mean annual air temperature (ΔT 10 ); the deviation smoothed over a 10-year interval (average value for the period from 1886 to 2005) (Hansen et al, 2010) was sourced from the global open-access climate database KNMI GISTEMP1200 (https://climexp.knmi.nl/plot_atlas_form.py) (Trouet and Van Oldenborgh, 2013).…”