The water-mass area along three hydrographic transects. The magnitude of linear trends estimated for each time series is shown in text with corresponding colour. WSBW areas computed along A12, SR4 and SR4 west (between 51 W and 30 W) and the Weddell Sea segment of A23 are illustrated, along with the WSDW area along the Scotia Sea part of A23. All the time series have statistically significant decreasing trends, with a notable connection between WSBW and Lower WSDW along A23. Error ranges are displayed and centred around the water-mass area as measured. The upper and lower bounds of error range account for combining the errors on neutral density field sourced from the instrumental uncertainties of both temperature (+/-0.001 C) and salinity (+/-0.002) sensors. The lower bounds are the water-mass area when temperature measurements apply a 0.001 C warming and salinity measurements apply a 0.002 freshening. The upper bounds are the water-mass area when temperature measurements apply a 0.001 C cooling and salinity measurements apply a 0.002 salinification ( Methods ).
