Yukon River incision drove organic carbon burial in the Bering Sea during global climate changes at 2.6 and 1Ma

Abstract

River erosion affects the carbon cycle and thus climate by exporting terrigenous carbon to seafloor sediment and by nourishing CO2-consuming marine life. The Yukon River-Bering Sea system preserves rare source-to-sink records of these processes across profound changes in global climate during the past 5 million years (Ma). Here, we expand the terrestrial erosion record by dating terraces along the Charley River, Alaska, and explore linkages among previously published Yukon River tributary incision chronologies and Bering Sea sedimentation. Cosmogenic 26Al/10Be isochron burial ages of Charley River terraces match previously documented central Yukon River tributary incision from 2.6 to 1.6Ma during Pliocene-Pleistocene glacial expansion, and at 1.1Ma during the 1.2-0.7Ma Middle Pleistocene climate transition. Bering Sea sediments preserve 2-4-fold rate increases of Yukon River-derived continental detritus, terrestrial and marine organic carbon, and silicate microfossil deposition at 2.6-2.1 and 1.1-0.8Ma. These tightly coupled records demonstrate elevated terrigenous nutrient and carbon export and concomitant Bering Sea productivity in response to climate-forced Yukon River incision. Carbon burial related to accelerated terrestrial erosion may contribute to CO2 drawdown across the Pliocene-Pleistocene and Middle Pleistocene climate transitions observed in many proxy records worldwide.