THE ARCTIC GREAT RIVERS OBSERVATORY (Invited Presentation)

Six large rivers, including the Yukon and Mackenzie in North America and the Yenisey, Ob, Lena, and Kolyma in Eurasia, drain roughly two thirds of the pan-arctic watershed. Seasonally-explicit sampling programs were initiated at downstream locations on these rivers during the early 2000s in order to 1) improve estimates of fluvial export to the Arctic Ocean and 2) establish benchmarks for tracking watershed-scale changes associated with global warming. Founded as the Pan-Arctic River Transport of Nutrients, Organic Matter, and Suspended Sediments (PARTNERS) project and later continued as the Arctic Great Rivers Observatory (Arctic-GRO), this effort has greatly improved estimates of water-borne constituent fluxes to the Arctic Ocean and helped to constrain end-member values for freshwater tracer applications and studies of biogeochemical transport/processing within the Arctic Ocean. This presentation highlights key findings from the Arctic-GRO, with an emphasis on particulate export. Although the North American rivers have much higher sediment yields than the Eurasian rivers, differences in particulate organic matter yields are less pronounced. This is primarily due to lower organic matter percentages contributing to sediment loads during peak discharge in the North American rivers. Roughly half of the organic nitrogen exported from arctic rivers is delivered to the Arctic Ocean in particulate form. This contrasts sharply with organic carbon export, which is strongly dominated by dissolved material in most of the major arctic rivers.