Oceanic heat flux ( F w ) is the vertical heat flux that is transmitted to the base of sea ice. It is the main source of sea ice bottom melting. The residual method was adopted to study oceanic heat flux under sea ice. The data acquired by 28 ice mass balance buoys (IMBs) deployed over the period of 2004 to 2013 in the Arctic Ocean were used. F w values presented striking seasonal and spatial variations. The average summer F w values for the Canada Basin, Transpolar Drift, and Multiyear Ice area were 16.8, 7.7, and 5.9 W m −2, respectively. The mean summer F w for the whole Arctic was 10.1 W m −2, which was equivalent to a bottom melt of 0.4 m. F w showed an autumn peak in November in the presence of the near-surface temperature maximum (NSTM). The average F w for October to December was 3.7 W m −2. And the average F w for January to March was 1.0 W m −2, which was approximately one third of the average F w in the presence of NSTM. The summer F w was almost wholly attributed to the incident solar radiation that enters the upper ocean through leads and the open water. F w calculated through the residual method using IMB data was compared with that calculated through the parameterization method using Autonomous Ocean Flux Buoy data. The results revealed that the F w provided by the two methods were consistent when the sea ice concentration exceeded 70% and mixing layer temperature departure from freezing point was less than 0.15°C. Otherwise, the F w yielded by the residual method was approximately one third smaller than that provided by the parameterization method.