Oxygen isotopic composition of bottom seawater and tunicate cellulose used as indicators of water masses in the northern Bering and Chukchi Seas

Abstract

Oxygen isotopic composition of bottom seawater and tunicate cellulose were used as short‐term and long‐term indicators, respectively, of water‐mass characteristics in the northern Bering and Chukchi Seas. Oxygen isotopic composition of northeastern Bering Sea waters is influenced by Yukon River inflows of 18O‐depleted continental water mixing with relatively 18O‐enriched waters contributed by the Anadyr Current. Tunicate cellulose sampled under Alaska coastal water is more depleted in 18O than that collected under Bering shelf and Anadyr waters, which reflects the oxygen isotopic composition of these waters. Tunicate cellulose collected under the mixed Bering shelf water displays intermediate δ18O values. Oxygen isotopic analyses of bottom seawater were used to determine the spatial location and influence of continental and coastal‐derived precipitation and of sea‐ice formation on water‐mass structure on the continental shelf of the northern Bering and Chukchi Seas. Results indicate that the oxygen isotopic composition of tunicate cellulose, averaged over multiple seasons, may serve as a long‐term biochemical indicator of water‐mass patterns in ice‐covered polar regions where continuous sampling is impractical.