Arctic river-runoff: mean residence time on the shelves and in the halocline

The mean residence time of river-runoff on the shelves and in the halocline of the Arctic Ocean is estimated from salinity and tracer data (tritium, ³He and the ¹⁸O/¹⁶O ratio). These estimates are derived from comparison of apparent tracer ages of the halocline waters using a combination of tracers that yield different information: (1) the tritium "vintage" age, which records the time that has passed since the river-runoff entered the shelf; and (2) the tritium/³He age, which reflects the time since the shelf waters left the shelf. The difference between the ages determined by these two methods is about 3-6 years. Correction for the initial tritium/³He age of the shelf waters (about 0.5-1.5 years) yields a mean residence time of the river-runoff on the shelves of the Siberian Seas of about 3.5 ± 2 years.