Denitrification and N2 fixation in the Pacific Ocean

作者：Curtis Anthony Deutsch, Nicolas Gruber, Robert M. Key, Jorge Louis Sarmiento, Alexandre Ganachaud · 发表于：Global Biogeochemical Cycles · 年份：2001 · DOI：10.1029/2000gb001291 · 被引用次数：374 · 研究领域：Marine and coastal ecosystems、Isotope Analysis in Ecology、Oceanographic and Atmospheric Processes

We establish the fixed nitrogen budget of the Pacific Ocean based on nutrient fields from the recently completed World Ocean Circulation Experiment (WOCE). The budget includes denitrification in the water column and sediments, nitrogen fixation, atmospheric and riverine inputs, and nitrogen divergence due to the large‐scale circulation. A water column denitrification rate of 48±5 Tg N yr −1 is calculated for the Eastern Tropical Pacific using N* [Gruber and Sarmiento, 1997] and water mass age tracers. On the basis of rates in the literature, we estimate sedimentary denitrification to remove an additional 15±3 Tg N yr−1. We then calculate the total nitrogen divergence due to the large scale circulation through the basin, composed of flows through a zonal transect at 32°S, and through the Indonesian and Bering straits. Adding atmospheric deposition and riverine fluxes results in a net divergence of nitrogen from the basin of −4±12 Tg N yr−1. Pacific nitrogen fixation can be extracted as a residual component of the total budget, assuming steady state. We find that nitrogen fixation would have to contribute 59±14 Tg N yr−1 in order to balance the Pacific nitrogen budget. This result is consistent with the tentative global extrapolations of Gruber and Sarmiento [1997], based on nitrogen fixation rates estimated for the North Atlantic. Our estimated mean areal fixation rate is within the range of direct and geochemical rate estimates from a single location near Hawaii [Karl et al.,...