Mapping dataset of dissolved oxygen and carbonate system comparing seasonal subsurface deoxygenation and acidification in the Yellow Sea and northern East China Sea in 2017-2018

Seven field surveys were conducted on Chinese side of the Yellow Sea and the northern East China Sea during 2017‒2018 (Table S1), spanning a wet summer (July‒August 2018) and a dry winter (December 2017‒January 2018), as well as those transitional seasons of spring (March‒May 2018) and autumn (October‒November 2017 and October‒November 2018). Water samples were collected at two to seven different depths (including sea surface and the bottom water) using 10 or 12 Niskin bottles, which were mounted with Conductivity-Temperature-Depth/Pressure (CTD) recorders. The ancillary data of in situ temperature (after the International Temperature Scale of 1990) and salinity (after the Practical Salinity Scale of 1978) were obtained primarily using the calibrated CTD recorders (SBE-19 plus in our October‒November 2017 and May 2018 cruises, and SBE-911 plus during the other cruises, Sea Bird Co., USA). During the summertime estuarine survey conducted in July 2018, salinity values of discrete samples were also measured using a calibrated WTW’s TetrCon^®925 probe.Sampling surveys were separately supported by the National Natural Science Foundation of China (via Ship-time Sharing projects during the Open Research Cruises conducted in the Bohai and Yellow Seas in 2017 and 2018, and in the Changjiang Estuary in 2018), the Yellow Sea Fisheries Research Institute of Chinese Academy of Fishery Sciences, and the First Institute of Oceanography, Ministry of Natural Resources, China.<br>