17:15 〜 18:45
[ACG41-P07] 長距離輸送アジアダストの供給源とその季節性および北太平洋の海洋基礎生産への影響
キーワード：アジアダスト、長距離輸送、供給源、季節性、海洋基礎生産
Dust significantly impacts the Earth’s environment by altering the global radiative balance, cloud properties, and marine primary production through iron supply (Maher et al., 2010). In East Asia, dust is emitted from the vast dry regions like the Taklimakan Desert in western China and the Gobi Desert in southern Mongolia (Sun et al., 2001). The westerlies transport dust particles from such deserts to the downwind countries and the northwestern North Pacific. They are sometimes transported more than one entire circuit around the globe through the westerly jet (Uno et al., 2009). While their potential impacts on mid-latitude climate and marine primary production in the North Pacific are acknowledged, the dominant source of long-distance (thousands of kilometers and more) transported dust and its seasonality has not been fully understood. Therefore, it is critical to investigate the provenance of the Asian dust transported over long distances and examine the dynamics.
Ice cores from Mt. Logan (60.6N, 140.6W), Canada, are the ideal recorder of seasonal to decadal-scale changes in dust transport over a long distance with a high accumulation rate (Zdanowicz et al., 2006). Here, we examine the past seasonal change of dust provenance using an ice core from King Col (4135m above sea level) at Mt. Logan by utilizing a unique provenance-tracing method, cathodoluminescence (CL) spectral analysis of single quartz grains (Nagashima et al., 2017, 2023). CL spectroscopy can detect crystal-chemical features in quartz, such as impurities and intrinsic imperfections that depend on the conditions affecting quartz from its formation onward. Nagashima et al. (2017, 2023) showed differences in CL-spectra for quartz particles between those from the Taklimakan Desert and the Mongolian Gobi. We conducted CL analysis using quartz particles in ice core samples covering 1985-1990 (6–9 samples/year). We found most samples show similar CL features to those of the Taklimakan Desert, except for several samples showing similarity to those of the Gobi Desert. We interpreted the results as suggesting the Taklimakan Desert is the primary source of long-distance transported dust throughout the year. In contrast, dust from the Gobi Desert has been transported following the strong spring dust events.
We will further compare our results with the amounts of seasonal dust emissions from the Taklimakan and Gobi deserts and deposition fluxes of long-distance transport dust from those deserts derived from numerical simulations of an atmospheric chemical transport model (IMPACT) and discuss the dynamics causing such differences between the deserts. In addition, we will explore the overall characteristics of long-distance transported Asian dust and its impact on marine primary production in the North Pacific.
Ice cores from Mt. Logan (60.6N, 140.6W), Canada, are the ideal recorder of seasonal to decadal-scale changes in dust transport over a long distance with a high accumulation rate (Zdanowicz et al., 2006). Here, we examine the past seasonal change of dust provenance using an ice core from King Col (4135m above sea level) at Mt. Logan by utilizing a unique provenance-tracing method, cathodoluminescence (CL) spectral analysis of single quartz grains (Nagashima et al., 2017, 2023). CL spectroscopy can detect crystal-chemical features in quartz, such as impurities and intrinsic imperfections that depend on the conditions affecting quartz from its formation onward. Nagashima et al. (2017, 2023) showed differences in CL-spectra for quartz particles between those from the Taklimakan Desert and the Mongolian Gobi. We conducted CL analysis using quartz particles in ice core samples covering 1985-1990 (6–9 samples/year). We found most samples show similar CL features to those of the Taklimakan Desert, except for several samples showing similarity to those of the Gobi Desert. We interpreted the results as suggesting the Taklimakan Desert is the primary source of long-distance transported dust throughout the year. In contrast, dust from the Gobi Desert has been transported following the strong spring dust events.
We will further compare our results with the amounts of seasonal dust emissions from the Taklimakan and Gobi deserts and deposition fluxes of long-distance transport dust from those deserts derived from numerical simulations of an atmospheric chemical transport model (IMPACT) and discuss the dynamics causing such differences between the deserts. In addition, we will explore the overall characteristics of long-distance transported Asian dust and its impact on marine primary production in the North Pacific.