(A) Time series of total heat content (J) relative to the freezing temperature integrated between the isohalines S = 31 and S = 33 in the BG region delineated by the cyan line in Fig. 2. (B) Time series of average thickness (m) (left y axis) and layer-averaged temperature (°C) (right y axis) of the layer bounded by S = 31 and S = 33 over the BG region.