Fig. 1
(a) Schematic of upper ocean circulation features. Blue and red arrows represent surface flows from the Pacific and Atlantic oceans, respectively. River discharge and transpolar drift (TPD) are indicated by light blue and broad orange arrows, respectively. The anticyclonic (clockwise) circulation over the Beaufort Sea represents the Beaufort Gyre (BG). The circulation features are based on the schematic from Charette et al.4. (b) The BG extent (BGEXT) (contours), the locations of the maximum dynamic ocean topography (DOTmax) within the study region (dots inside the gyre), and the strength of the BG (BGSTR) (as indicated in the legend) from 2017 to 2022. The BGEXT is defined as the largest closed contour of the dynamic ocean topography (DOT), corresponding to the minimum DOT (DOTmin) surrounding DOTmax. The BGSTR is calculated as the difference between DOTmax and DOTmin, divided by the mean radius of the BG. (c) Locations of sampling stations. White and black circles represent seawater sampling stations in the summers of 2019 and 2022, respectively. Geographic locations are divided into two regions: the East Siberian Sea and the Chukchi Borderland. The red line labeled “T1” refers to the hydrographic transect shown in Fig. 2. The Arctic maps in this figure were created using Python 3.9.19 (https://www.python.org/) with matplotlib 3.8.4 (https://matplotlib.org/) and basemap 1.4.1 (https://matplotlib.org/basemap/).
