The oceans are experiencing unprecedented rates of change associated with climate change and human activities. Amongst the many marginal seas of the global ocean, the East Asian marginal seas, including the East/Japan Sea (EJS), Yellow Sea (YS), East China Sea (ECS), and South China Sea (SCS), are likely to be the most heavily influenced by anthropogenic activities. These marginal seas receive massive amounts of allochthonous materials via submarine groundwater discharge as well as large rivers, including the Changjiang and the Yellow River, and are subject to substantial atmospheric forcing by their location beneath the westerlies (i.e., Nakamura et al., 2005; Lee and Kim, 2007; Müller et al., 2008; Jiang et al., 2014; Park et al., 2019). The human footprint in these seas is amplified because the residence times of the YS (about 5 years, water volume: 9.96×1012 m3, average water depth: 44 m) and the EJS (about 100 years, water volume: 1.68×1015 m3, average water depth: 1680 m) are relatively shorter than the major oceans (Nozaki et al., 1991; Tsunogai et al., 1993) (Figure 1). This means that the external inputs have a significant impact on the marginal seas. Vigorous biogeochemical alterations occur in the YS and the ECS, which compose one of the largest continental shelves in the world (Kim et al., 2018; Cho et al., 2019; Han et al., 2022). These shelf waters eventually influence the euphotic zone of the EJS and the adjacent Pacific Ocean. On the other hand, the EJS has its own deep water ventilation system and various oceanographic features that are similar to those of the global ocean, such as numerous eddies, subpolar thermal fronts, brine rejection, and deep convection (Kim et al., 2001; Senjyu et al., 2002; Talley et al., 2003; Lee et al., 2019). Since these marginal seas are at the forefront of our human interaction with the marine environment, there is a pressing need to explore the responses of physics and biogeochemistry in these seas to climate change and human impacts.