5:15 PM - 7:15 PM
[MIS14-P10] Changes in freshwater inflow off the mouth of the Mackenzie River in the Arctic Ocean over the past 600 years based on fatty acid hydrogen isotope ratios.
Keywords:Arctic sea, isotope ratio
The Mackenzie River, the largest river flowing into the western Arctic Ocean, is remarkable for its catchment area (1.8 * 106 km2), summer discharge (15,290 m3/s) and sediment discharge (about 127 Mt/year). The river accounts for about 10% of the Arctic Ocean's riverine inflow, and since 2003, freshwater discharge has increased by 25% and the amount of suspended sediment and organic carbon transported has increased by 50%. Increased river inflow strengthens the stratification of the Arctic Ocean and promotes sea ice formation in winter, while the warming by river water in summer promotes higher sea surface temperatures and sea ice melting.
In this study, we reconstructed the freshwater contribution to the western Arctic Ocean by the Mackenzie River over 600 years using fatty acid hydrogen isotope ratios in MT1 sediment cores collected during the 2022 HAPPI (Holocene Arctic Palaeoclimate and Palaeocean Investigation) expedition of R/V Mirai of JAMSTEC.
The δD values of C16 fatty acids varied between -240‰ and -180‰, with a maximum around 1550, followed by a gradual decrease of 20‰ with an oscillation of several decades until around 1800, after which the decrease became steeper. After about 1800, the decrease became steeper and reached 40‰ by 2022. By using the δD values of Atlantic water in the Arctic Ocean and river water in the Mackenzie River as the edge components of seawater and freshwater, and correcting for the effect of salinity on the δD of C16 fatty acids, it is estimated that the summer surface freshwater volume increased by 16% and salinity decreased by 6 psu since 1800.
In this study, we reconstructed the freshwater contribution to the western Arctic Ocean by the Mackenzie River over 600 years using fatty acid hydrogen isotope ratios in MT1 sediment cores collected during the 2022 HAPPI (Holocene Arctic Palaeoclimate and Palaeocean Investigation) expedition of R/V Mirai of JAMSTEC.
The δD values of C16 fatty acids varied between -240‰ and -180‰, with a maximum around 1550, followed by a gradual decrease of 20‰ with an oscillation of several decades until around 1800, after which the decrease became steeper. After about 1800, the decrease became steeper and reached 40‰ by 2022. By using the δD values of Atlantic water in the Arctic Ocean and river water in the Mackenzie River as the edge components of seawater and freshwater, and correcting for the effect of salinity on the δD of C16 fatty acids, it is estimated that the summer surface freshwater volume increased by 16% and salinity decreased by 6 psu since 1800.