Fig. 5

Boxplots of (a) river water fraction and (b) terrestrial-derived FDOM (C2) (R.U) in the surface waters (< 50 m) of the Chukchi Borderland (CBL) and East Siberian Sea (ESS) at the 18 selected stations (12 in the CBL and 6 in the ESS) where samples were collected in both 2019 (red) and 2022 (blue) (see Fig. 1c for the selected sampling locations). Asterisks above the boxplots indicate statistically significant differences between the two years (p < 0.001).