Global distribution and sources of dissolved inorganic nitrogen export to the coastal zone: Results from a spatially explicit, global model

Abstract

Here we describe, test, and apply a spatially explicit, global model for predicting dissolved inorganic nitrogen (DIN) export by rivers to coastal waters (NEWS‐DIN). NEWS‐DIN was developed as part of an internally consistent suite of global nutrient export models. Modeled and measured DIN export values agree well (calibration R 2 = 0.79), and NEWS‐DIN is relatively free of bias. NEWS‐DIN predicts: DIN yields ranging from 0.0004 to 5217 kg N km −2 yr −1 with the highest DIN yields occurring in Europe and South East Asia; global DIN export to coastal waters of 25 Tg N yr −1 , with 16 Tg N yr −1 from anthropogenic sources; biological N 2 fixation is the dominant source of exported DIN; and globally, and on every continent except Africa, N fertilizer is the largest anthropogenic source of DIN export to coastal waters.