Abstract: Links between organic carbon preservation, sea ice condition and oceanic current distribution in the Arctic Ocean are reported through analysis of Mn and Ca content, grain-size composition, content and isotopic composition of organic carbon in sediments from core 08B85-D collected at Alpha Ridge, Arctic Ocean. Glacial-interglacial cycles in sedimentary layers of organic carbon content are not apparent. Four sources of organic carbon are identified, with concentration in sediments controlled primarily by sea ice density and the strength of Beaufort Gyre. During several periods in MIS7, sea ice density in the western Arctic appears to have been low and the Beaufort Gyre particularly active, resulting in transportation of terrestrial-sourced organic carbon to the Alpha Ridge. To the contrary, in that time between MIS6 and MIS1 (especially MIS6 and MIS4–MIS3), the contribution of oceanic organic carbon to sediments exceeds that of the terrestrial carbon, during a time dense sea ice likely restricted transport of terrestrial organic carbon by limiting the Beaufort Gyre.

Key words: Arctic Ocean, Alpha Ridge, source of organic carbon, Beaufort Gyre