Sedimentary record of sea ice rafting in the Laptev Sea during the Holocene: Evidence from the improved ice rafting debris (IRD) proxy

Variations in sea ice have important implications for climate and local ecosystems, as well as the sediment budget in the Arctic Ocean, and reconstructing the evolutionary history of sea ice is currently a subject undergoing intense study. Extracting credible sea ice signals from complex sedimentary records is key to accurately reconstructing sea ice variability. Although the coarse sediment fraction is commonly used to reconstruct the variability of sea ice, relying on the coarse fraction alone in the Arctic shelf region poses challenges because of the drastic changes in the depositional environment that followed deglaciation. Here, we conduct chronological, sedimentary, and geochemical analyses of two sediment cores (LV83-16-1 and LV83-32-3) from the eastern central Laptev Sea and Lena River-Yana River estuary. We propose the "anomalous" pattern-an increasing coarse fraction content in the sediment with a negative skewness-as an indicator of sea ice deposits. We then apply this proxy to reconstruct the history of sea ice rafting deposits during the Holocene in the Laptev Sea. The results show that the onset of sea ice rafting deposits occurs at 6700 cal. yr. BP in the central shelf and at 4300 cal. yr. BP in the Lena River estuary. After 6700 cal. yr. BP, the central shelf region shows an increasing trend in sea ice sediment contribution, which is likely linked to weakening solar radiation. In addition, sea ice rafting deposits exhibit millennial-scale fluctuations, with increased contributions at 6700-3500 cal. yr. BP and 2000-1000 cal. yr. BP and a decreased contribution at 3500-2000 cal. yr. BP. These millennial-scale fluctuations are likely related to changes in Atlantic warm water inflow. Note that peaks in sea ice sediment contribution coincide with increased summer air temperatures at 5400, 3700, and 1200 cal. yr. BP. During the last 1000 cal. yr. BP, the sea ice sediment transport has been restricted and the riverine sediment transport beneath the sea ice is likely to increase.