The composition and origination of particles from surface water in the Chukchi Sea, Arctic Ocean

Suspended particle samples were collected at 11 stations on the shelf and slope regions of the ChukchiSea and the central Arctic Ocean during the fifth Chinese National Arctic Research Expedition(summer 2012). The particle concentration, total organic carbon(TOC), total nitrogen(TN) and the isotopic composition of the samples were analyzed. The suspended particle concentration varied between 0.56 and 4.01 mg.L-1; the samples collected from the sea ice margin have higher concentrations. The organic matter content is higher in the shelf area(TOC: 9.78%–20.24%; TN: 0.91%–2.31%), and exhibits heavier isotopic compositions(δ13C: –23.29‰ to –26.33‰ PDB; δ15N: 6.14‰–7.78‰), indicating that the organic matter is mostly marine in origin with some terrigenous input. In the slope and the central Arctic Ocean, the organic matter content is lower(TOC: 8.06%–8.96%; TN: 0.46%–0.72%), except for one sample(SR15), and has lighter isotopic compositions(δ13C: –26.93‰ to –27.78‰ PDB; δ15N: 4.13‰–4.84‰). This indicates that the organic matter is mostly terrestrially-derived in these regions. The extremely high amount of terrigenous organic matter(TOC: 27.94%; TN: 1.16%; δ13C: –27.43‰ PDB; δ15N: 3.81‰) implies that it was carried by transpolar currents from the East Siberian Sea. Material, including sea ice algae, carried by sea ice are the primary source for particles in the sea ice margins. Sea ice melting released a substantial amount of biomass into the shelf, but a large amount of detrital and clay minerals in the slope and the central Arctic Ocean.