Dissolved methane in the Chukchi Sea during 2017-2020

<p>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.</p> <p>Seawater samples for CH₄ analysis were collected onboard R/V &ldquo;Xuelong 1&rdquo;, &ldquo;Xuelong 2&rdquo;, and &ldquo;Xiangyanghong 3&rdquo; during the 8-11th Chinese Arctic Research Expedition (CHINARE) to the Chukchi Sea during 2017-2020.</p> <p>1. Equipment:</p> <ul> <li>Name gas chromatography</li> <li>Model: Agilent 7890A</li> <li>Method: purge-and-trap</li> <li>Calibration: CH₄:N₂ mixtures, China Institute of Metrology</li> </ul> <p>2 Sampling and analysis</p> <p>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 &deg;C after adding 180 &mu;L of saturated HgCl₂.</p> <p>3 Location</p> <p>The Chukchi Sea.</p>