Aerosol in global oceanic regions: Four-decade trends, spatial patterns, and policy implications

Area of Science:

• Atmospheric Science
• Environmental Science
• Remote Sensing

Background:

• High aerosol loadings impact both continental megacities and oceanic regions, such as the Bohai Sea.
• Understanding spatial and temporal variations in oceanic Aerosol Optical Depth (AOD) is crucial for air quality assessment.

Purpose of the Study:

• To comprehensively analyze global oceanic Aerosol Optical Depth (AOD) variations over the past four decades.
• To identify trends and regional differences in oceanic aerosol pollution.
• To investigate factors influencing AOD changes in inland seas.

Main Methods:

• Utilized remote sensing reanalysis data for a four-decade analysis of AOD.
• Analyzed spatial distributions, latitudinal variations, and temporal trends of AOD.
• Compared AOD levels in inland seas with adjacent oceanic regions.

Main Results:

• Global oceanic AOD shows a decreasing trend across 89.5% of grids over four decades.
• Higher AOD values are concentrated in the Northern Hemisphere, with the Bohai Sea exhibiting the highest pollution levels (AOD ~0.35).
• AOD is increasing in low-latitude oceanic areas (30° S-30° N) and sharply in Asian inland seas, with the Bohai Sea showing a 1.4% annual increase.

Conclusions:

• While global oceanic aerosol pollution is declining, specific regions like the Bohai Sea face worsening air quality.
• Emission control policies on adjacent continents have influenced AOD trends in inland seas.
• Strategic industrial relocation away from coastal cities could improve air quality in polluted inland seas.