Modern Deposition of Atmospheric Dust in the Northeast Indian Ocean

Abstract

Atmospheric dust in the ocean is a bridge for air-sea interaction, which is an important basis for the study of this phenomenon due to extensive and observable space-time scales. The northeast Indian Ocean, located in the southern wing of the "roof of the world," the Tibetan Plateau, is among the seas with the strongest marine productivity and richest biodiversity in the world. However, there have been no relevant reports on the study of modern marine dust. This study discussed the modern process of atmospheric dust deposition in the northeast Indian Ocean for the first time, in terms of deposition flux, transport path simulation, scanning electron microscopy, and energy spectrum analysis based on atmospheric dust samples collected from September to November 2020 in the study area. The findings showed that the dust deposition flux in the northeast Indian Ocean varied between 221-1,221 mg/cm2/d. The maximum daily dust deposition fluxes appeared in the middle of November when winter monsoon conditions prevailed, and the minimum value appeared in late September under summer monsoon conditions; the former flux was approximately six times that of the latter. The dust deposition flux change was primarily affected by the distance of the dust source, whereas the dust particle size was related to wind intensity. The results of air particle simulation indicate that the dust transport process is controlled by seasonal and regional atmospheric circulation systems, and is specifically dominated by the Indian monsoon in the northeast Indian Ocean. The study area deposits more dust with nutrient elements from the Asian continent, which promotes the ocean's primary productivity and enhances its carbon sequestration capacity. Furthermore, the surface of quartz particles from modern atmospheric dust shows a unique structure in the aeolian environment, good quartz grain roundness, a meander ridge, and a U-shape. These characteristics are markedly different from those in a fluvial condition, such as poor roundness, conchoidal fracture, and a V-shape, which can be used as a reference to distinguish the different continental components in the sediments in the hope of establishing winter monsoon proxies in the northeast Indian Ocean to reconstruct the evolution of the Indian monsoon. This study not only fills a gap in the present-day dust deposition process in the northeast Indian Ocean but also provides new insight for dust research in the study area, with great scientific significance for the study of air-sea interaction and carbon sinks in the ocean, and ideal indicators for reconstructing the evolution of the paleo-Indian monsoon and changes in the paleo-ocean environment. Moreover, it offers important information for the reconstruction of the historical evolution and dynamic mechanism of the ancient Indian monsoon.

Keywords

• northeast indian ocean
• atmospheric dust in the ocean
• dust deposition
• modern process
• air-sea interaction