Sedimentary record of climate change in a high latitude fjord—Kongsfjord

The sedimentary record of climate change in the Arctic region is useful for understanding global warming. Kongsfjord is located in the subpolar region of the Arctic and is a suitable site for studying climate change. Glacier retreat is occurring in this region due to climate change, leading to an increase in meltwater outflow with a high debris content. In August 2017, we collected a sediment Core Z3 from the central fjord near the Yellow River Station. Then, we used the widely used chronology method of ²¹⁰Pb, ¹³⁷Cs, and other parameters to reflect the climate change record in the sedimentary environment of Kongsfjord. The results showed that after the mid-late 1990s, the mass accumulation rate of this core increased from 0.10 g/(cm²·a) to 0.34 g/(cm²·a), while the flux of ²¹⁰Pb_ex increased from 125 Bq/(m²·a) to 316 Bq/(m²·a). The higher sedimentary inventory of ²¹⁰Pb_ex in Kongsfjord compared to global fallout might have been caused by sediment focusing, boundary scavenging, and riverine input. Similarities between the inventory of ¹³⁷Cs and global fallout indicated that terrestrial particulate matter was the main source of ¹³⁷Cs in fjord sediments. The sedimentation rate increased after 1997, possibly due to the increased influx of glacial meltwater containing debris. In addition, the ¹³⁷Cs activity, percentage of organic carbon (OC), and OC/total nitrogen concentration ratio showed increasing trends toward the top of the core since 1997, corresponding to a decrease in the mass balance of glaciers in the region. The results of δ¹³C, δ¹⁵N and OC/TN concentration ratio showed both terrestrial and marine sources contributed to the organic matter in Core Z3. The relative contribution of terrestrial organic matter which was calculated by a two-endmember model showed an increased trend since mid-1990s. All these data indicate that global climate change has a significant impact on Arctic glaciers.