Figure 1. Freshwater flux fields used to force the model simulations [a-c]. Southern Ocean sectoral division is shown in [a]. Plotted in [d] are the zonal distributions of freshwater fluxes that are integrated meridionally. The blue band marks the location of the Antarctic Peninsula (AP). Plotted in [e] is the distribution of the zonally integrated freshwater fluxes, as a function of the meridional distance from the Antarctic Coast.
2.4 Increased ice melting experiment
Recent observational studies showed that AIS melting increased 10% ~ 40% from 1994 to 2018 [Rignot et al., 2019; Adsumilli et al 2020 ]. It has been suggested that the enhanced AIS melting rate is responsible for the observed AABW freshening in the last three decades [e.g., Anilkumar et al, 2021 ]. To test if the enhanced AIS melting can explain the observed freshening trend in AABW [Menezes et al, 2017; Shimada et al, 2012 ], we performed another simulation (VARI120% ). Starting from the initial conditions, VARI120% adds 2490 Gt/yr of freshwater into the Antarctic coastal waters, a 20% increase in total melting fromVARI . Strong open-ocean deep convection occurs in the first 100 years of both VARI and VARI120%, mixing the surface freshwater from AIS melting within the deeper water column (Fig S3). As a result, no surface freshening signal occurs in the first 100 years. For this reason, the transient AABW response to increased AIS melting (VARI vs VARI120%, section 3.2) was analyzed only after year 100 (Fig 3a).