Summertime freshwater fractions in the surface water of the western Arctic Ocean evaluated from total alkalinity

As a quasi-conservative tracer, measures of total alkalinity (TA) can be utilized to trace the relative fractions of freshwater and seawater. In this study, based on the TA and related data collected during the third Chinese National Arctic Research Expedition (July-September 2008, 3rd CHINARE-Arctic) and the fourth Chinese National Arctic Research Expedition (July- September 2010, 4th CHINARE-Arctic), fractions of sea-ice meltwater, river runoff, and seawater within the surface water of the western Arctic Ocean were determined using salinity and TA relationships. The largest fraction of sea-ice meltwater was found around 75°N within the Canada Basin during both surveys, which is located at the ice edge. Generally, it was found that the frac- tion of river runoff was less than that of sea-ice meltwater. The river runoff, composed mainly of contributions from the Yukon River carried by Bering inflow water and the Mackenzie River, was influenced by the currents, leading to two peak areas of its fraction. Our results show that the dilution effect of freshwater carried by Bering inflow water during the 3rd CHINARE-Arctic in 2008 expedition period may be stronger than that during the 4th CHINARE-Arctic in 2010 expedition period. The peak area of sea-ice meltwater fraction during the 4th CHINARE-Arctic was different from that of the 3rd CHINARE-Arctic, corresponding to their sea-ice condition.