Arctic Neodymium Isotope Traces for the Atlantic Water Layer at the Chukchi Continental Margin

Yang Ying; Ye Liming; Ni Jianyu; Yu Xiaoguo; Yuan Chao; Ge Qian; Song Sai; Zhang Yongcong

doi:10.3799/dqkx.2023.045

Abstract：In the Arctic Ocean,the Atlantic water layer is an essential source of heat that regulates sea ice,ice shelves,and surrounding ice sheets.By analyzing the content and pattern of rare earth elements(REE)and Nd isotopic composition(εNd)in the sediments of Hole M04 and its distribution pattern and Nd isotopic composition of Fe-Mn oxide fraction,this study explores the enrichment mechanism of REE on the edge of Chukchi shelf since Late Pleistocene,the effectiveness of εNd tracer water mass properties,and the strength and weakness of the"Atlantic water layer".The records indicate that Fe-Mn oxides were the primary carriers for dissolved REE during the interglacial period,but a large quantity of dissolved REE was also enriched in the gray layer lacking Fe-Mn oxides.In addition,there is a significant spike of εNd in Fe-Mn oxide leachate during the glacial period and a drop during the interglacial period corresponding to values between-5.50 and-8.74.Therefore,we conclude that the Atlantic water layer strengthened during the interglacial period,which allowed re-oxidation of Fe2+and Mn2+input from the shelf,but withdrew almost entirely from the Chukchi continental margin during the glacial period.Similar to the chemical composition of modern glacial meltwater,the development of the East Siberian ice sheet and its subglacial drainage are more likely to lead to the REE enrichment and εNd positive bias in Core M04 Fe-Mn oxide extraction solution than sea ice production brine.These findings further illustrate the process of enrichment of REEs in the Arctic Ocean,demonstrate the effectiveness of εNd as a marker of the Atlantic water layer,and contribute to an understanding of the Atlantic water layer evolution.