During the second half of the twentieth century, the Antarctic Peninsula exhibited a rapid increase in air temperatures. This was accompanied by a reduction in sea ice extent, increased precipitation and a dramatic retreat of glaciers associated with an increase in heat flux from deep ocean water masses. Isotopic tracers have been used previously to investigate the relative importance of the different freshwater sources to the adjacent Bellingshausen Sea, but the data coverage is strongly biased toward summer and unambiguous determination of the different meteoric water contributions remains challenging. Here a high-resolution model is used to investigate the ocean's response to the observed changes in its different freshwater inputs (sea ice melt/freeze, precipitation/evaporation, iceberg melt, ice shelf melt and glacier melt). By developing the code to enable tracing of the sources and pathways of the individual components of the freshwater budget, it is shown that sea ice dominates the seasonal changes in freshwater content, but all sources contribute approximately equally to annual-mean freshwater fluxes and interannual freshwater flux anomalies. Ice shelf melting is shown to be the largest contributor to freshwater content on the annual mean. Decadal trends in the salinity and stratification of the ocean are investigated, and a 20-year surface freshening trend is found to be predominantly driven by decreasing autumn sea ice growth. By partitioning the freshwater in this way, insight is gained into the long-term freshwater balance and variability, and therefore the potential effects of a changing climate.