Recently, Researcher He Xianqiang from the State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, and his collaborators published a research paper entitled Divergent Hemispheric Trends in Marine Dust Deposition Over the Past Two Decades in Science Bulletin (Impact Factor = 21.1).
Researcher He Xianqiang serves as both the first author and corresponding author, and Dr. Song Zigeng from Xiamen University of Technology is the co-first author. Other collaborators include Researcher Bai Yan, Researcher Wang Difeng, Associate Researcher Li Teng, Senior Engineer Gong Fang and Associate Researcher Jin Xuchen from the laboratory, Professor Wei-Jun Cai from University of Delaware in the United States, and Professor Palanisamy Shanmugam from Indian Institute of Technology Madras.
Dust transported from terrestrial arid regions to the ocean is rich in nutrients such as iron, nitrogen and phosphorus, acting as natural nutrients for marine ecosystems and playing a crucial role in phytoplankton growth and carbon sequestration via marine primary production. Nevertheless, there is still a lack of systematic and comprehensive understanding of the long-term variation rules of global marine dust deposition and its impacts on marine ecology. To address this scientific problem, the team established a dust deposition flux estimation model based on CALIPSO spaceborne lidar observations, and constructed remote sensing datasets of global marine dust deposition flux (DDF) and three-dimensional dust mass concentration (DMC) from 2007 to 2021.
Based on the long-term datasets, the study found that marine dust deposition flux in the Northern and Southern Hemispheres has shown opposite variation trends in the past two decades. Dust deposition has declined in most sea areas of the Northern Hemisphere while increased remarkably in the Southern Hemisphere, with an annual growth rate of 3% to 8% in partial waters. The divergent trends are closely associated with changes in precipitation and vegetation coverage of adjacent land areas. Rising precipitation and vegetation coverage in the Northern Hemisphere have curbed dust emission. On the contrary, reduced precipitation and decreased vegetation coverage in Australia and southern Africa have boosted dust emissions, leading to increased dust deposition in the Southern Hemisphere.
The research further quantified the contribution rates of long-term variations of dust deposition flux (DDF), sea surface temperature (SST), mixed layer depth (MLD) and photosynthetically active radiation (PAR) to the evolution of phytoplankton chlorophyll-a concentration (CHL) and net primary productivity (NPP) in five major global ocean regions excluding the Arctic Ocean. The results indicated that SST ranks first in contribution among the four influencing factors, yet DDF takes the leading position in the Southern Ocean with a contribution rate up to 36%. In the other four ocean regions, DDF is the second major factor affecting chlorophyll-a concentration variation, and its contribution rate exceeds 30% in both the Atlantic Ocean and the Indian Ocean.
This study clarifies the opposite variation trends of marine dust deposition in the two hemispheres over the past 20 years, which are closely correlated with the reversed changes of terrestrial precipitation and vegetation coverage between the Northern and Southern Hemispheres. It proves that terrestrial environmental changes can significantly affect the biomass and carbon sequestration capacity of global marine phytoplankton.
Fig.1 Spatial distribution of DDF, DDF variation rate and DMC at different altitudes. (a) Spatial distribution of average DDF during 2007–2021 based on CALIPSO observations, dots represent the corresponding measured DDF values, and the zonal profile on the left stands for longitude-averaged DDF. (b) Spatial distribution of relative variation rate of DDF during 2007–2021, the left zonal profile shows longitude-averaged relative variation rate, and shaded areas indicate significant variations of DDF (p<0.05). Dark gray areas around South America are regions without valid CALIPSO observation data. (c) Three-dimensional spatial distribution of annual mean DMC at altitudes of 0–10 km.
Fig.2 Driving factors of DDF variations and their influences on global marine phytoplankton. (a)–(c) Spatial distribution of relative variation rates of global terrestrial fractional vegetation cover (FVC), total precipitation (TP) and dust emission (DE) during 2007–2021. Shaded areas on land represent areas with significant changes (p<0.05), and dark gray areas refer to data-free areas. The left zonal profile shows the longitude-averaged relative variation rates. (d) Spatial distribution of relative variation rate of chlorophyll-a concentration (CHL). (e) Spatial distribution of contribution rate of DDF to CHL changes, black areas around South America have no valid CALIPSO observation data. (f) Contribution rates of four influencing factors including sea surface temperature (SST), DDF, mixed layer depth (MLD) and photosynthetically active radiation (PAR) to CHL variations in global sea areas.
Citation
Xianqiang He, Zigeng Song, Yan Bai, Wei-Jun Cai, Palanisamy Shanmugam, Difeng Wang, Teng Li, Fang Gong, Xuchen Jin. Divergent hemispheric trends in marine dust deposition over the past two decades. Science Bulletin, 2025,
https://doi.org/10.1016/j.scib.2025.11.025.
