Dissolved methane in the Chukchi Sea during 2017-2020

Methane (CH₄) is one of the important greenhouse gases. CH₄ dry mole fractions in the atmosphere have increased continuously since the onset of the industrial revolution, contributing to more than 20% of the anthropogenic radiative forcing in the lower atmosphere since 1750. In addition, the ice-covered parts of the Arctic are now known to be a reservoir of organic carbon, suggesting that the coastal areas in the Arctic may be a neglected but essential component of the global CH₄ budget. Seawater samples for CH₄ analysis were collected onboard R/V “Xuelong 1”, “Xuelong 2”, and “Xiangyanghong 3” during the 8-11th Chinese Arctic Research Expedition (CHINARE) to the Chukchi Sea during 2017-2020. 1. Equipment: Name gas chromatography Model: Agilent 7890A Method: purge-and-trap Calibration: CH₄:N₂ mixtures, China Institute of Metrology 2 Sampling and analysis The samples were collected with a rosette water sampler equipped with Niskin bottles. Briefly, seawater was transferred to biochemical-oxygen-demand bottles (one for each depth), which were stored in the dark at 4 °C after adding 180 μL of saturated HgCl₂. 3 Location The Chukchi Sea.