Terrigenous organic matter sources and reactivity in the North Atlantic Ocean and a comparison to the Arctic and Pacific oceans

Lignin phenol concentrations and compositions in suspended particulate and dissolved organic matter (POM and DOM) were determined in samples from several locations and depths in the western North Atlantic Ocean. POM lignin phenol concentrations were 2-fold lower than previous measurements in the Pacific Ocean, but represented up to 28% of the total lignin phenols in the water column. Carbon-normalized yields of lignin phenols and δ13C measurements of POM indicate that up to half of the suspended material in deep water is of terrigenous origin and appears to enter the ocean via atmospheric deposition. This finding emphasizes the need for future research into aerosol compositions and fluxes into the oceans. In contrast to POM, DOM lignin phenol concentrations were 2-fold higher in the Atlantic, with more than two thirds in the high-molecular weight (HMW; > 1 kDa) fraction. Elevated concentrations of dissolved lignin phenols in North Atlantic Deep Water (NADW) indicated that 10–16% of annual fluxes of terrigenous DOM from Arctic rivers could be entrained during NADW formation. The percentage of lignin phenols in the HMW fraction decreases progressively from the Arctic to Atlantic to Pacific Oceans, reflecting an increasing diagenesis of terrigenous DOM. The average residence time of lignin phenols in the Atlantic is 35 years. Terrigenous DOC accounts for 1–2% of the DOC in surface and deep waters of the North Atlantic.