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Figure 1. 

Global and oceanic reactive nitrogen emissions in 2015. (a), (b) NH₃ and NO_x emissions from all sources (land and ocean); (c), (d) NH₃ and NO_x emissions from oceanic (marine) sources only, as a subset of the global totals.

Figure 2. 

Comparisons of observed and simulated wet nitrogen deposition fluxes. The first row shows NO₃⁻ wet deposition, and the second row shows NH₄⁺ wet deposition in units of kg N ha⁻¹ a⁻¹. Model results are sampled along the observational stations from the NADP, EMEP, EANET, and combined networks.

Figure 3. 

(a) Model simulated spatial distribution of oceanic nitrogen deposition in 2015 and projected changes under future 2050 emission scenarios, including (b) SSP126, (c) SSP370, and (d) SSP434. The inset values are the total global oceanic nitrogen deposition or total changes (percentage changes in parentheses) relative to the 2015 condition.

Figure 4. 

Nitrogen deposition characteristics in representative ocean regions for 2015 and three 2050 scenarios. The underlying map shows geographic locations of ocean regions (also shown in Supplementary Fig. S1) investigated, including coastal areas (1^st row from left to right: US coast, European coast, Indian coast, and China coast) and open oceans (2^nd row from left to right: Western Atlantic Ocean, East Atlantic Ocean, North Indian Ocean, and North Pacific Ocean). In each panel, bars represent nitrogen deposition components (dry NH_x, wet NH_x, dry NO_y, and wet NO_y deposition) for 2015 and three future emission scenarios (SSP126, SSP370, and SSP434 for 2050). Pie charts show shares of dry vs wet deposition (1^st row) and NH_x vs NO_y deposition (2^nd row). All deposition values are expressed in kg N ha⁻¹ a⁻¹.

Figure 5. 

Responses of oceanic nitrogen deposition to varying levels of anthropogenic NH₃, NO_x, and Nr emission reductions over the European coast (1^st row) and Eastern Atlantic Ocean (2^nd row) under the SSP126 2050 scenario. Relative changes in each nitrogen deposition component, including dry NH_x (blue solid), wet NH_x (blue dashed), dry NO_y (red solid), and wet NO_y (red dashed) driven by individual NH₃ emission reductions (left column), NO_x emission reductions (middle column), and joint Nr (NO_x and NH₃) emission reductions (right column). The inset numbers show the corresponding percentage changes for the specific reduction levels.