2015/11/05 by Karla P. Knudson, K. P. Knudson, Ana Christina Ravelo
Earth and Planetary Sciences · Environmental Science · #Geology and Paleoclimatology Research #Isotope Analysis in Ecology #Geological formations and processes
paper · pdf · doi:10.1002/2015gl066317
Abstract The relationship between climate, biological productivity, and nutrient flux is of considerable interest in the subarctic Pacific, which represents an important high‐nitrate, low‐chlorophyll region. While previous studies suggest that changes in iron supply and/or physical ocean stratification could hypothetically explain orbital‐scale fluctuations in subarctic Pacific nutrient utilization and productivity, previous records of nutrient utilization are too short to evaluate these relationships over many glacial‐interglacial cycles. We present new, high‐resolution records of sedimentary δ 15 N, which offer the first opportunity to evaluate systematic, orbital‐scale variations in subarctic Pacific nitrate utilization from 1.2 Ma. Nitrate utilization was enhanced during all glacials, varied with orbital‐scale periodicity since the mid‐Pleistocene transition, was strongly correlated with enhanced aeolian dust and low atmospheric CO 2 , but was not correlated with productivity. These results suggest that glacial stratification, rather than iron fertilization, systematically exerted an important regional control on nutrient utilization and air‐sea carbon flux.