In the context of climate change, sea surface temperature rises and sea ice melts. These environmental factors may have important effects on sea salt aerosols (SSA) and methanesulfonic acid (MSA). At the same time, SSA and MSA may further affect climate by reflecting and scattering solar radiation or forming cloud condensation nuclei. Therefore, exploring the temporal and spatial distribution characteristics of SSA and MSA concentrations in different sea areas under the background of climate change, as well as the key factors affecting their concentrations, is conducive to further understanding climate change and its interactions. In this thesis, 525 aerosol samples (in total) were collected from 6 cruises from the Arctic and 9 cruises from Antarctic during the Chinese National Arctic and Antarctica Research Expeditions to explore the spatial and temporal distribution characteristics of SSA and MSA concentrations during the summer periods across 2008-2020. Combined with the global chemical transport model GEOS-Chem, the simulation performance of SSA in different sea areas was evaluated, and a potential improvement mechanism was proposed. In addition, the key processes and main controlling factors affecting the concentration of MSA over the Arctic Ocean, the Bering Sea, the Northwest Pacific Ocean, and the Southern Ocean were investigated by combining the air mass backward trajectory and satellite data. It provides a scientific basis for understanding the relationship between climate change and SSA and MSA. The main research results are as follows:

(1) Based on aerosol samples collected during the Chinese National Polar Research Expeditions from 2008 to 2018, the spatial and temporal distribution characteristics and influencing factors of SSA in the Arctic Ocean, the Bering Sea, the Northwest Pacific Ocean, Southeast Asia, the eastern Indian Ocean, the Western Pacific Ocean, and the Southern Ocean were investigated. The results showed that there were significant differences in the SSA concentration at different latitudes, and its concentration in the Arctic Ocean was significantly lower than other sea areas. The SSA concentration in the Bering Sea in 2016 was significantly higher than that in 2012, and the interannual variation trend of the SSA concentration in the Arctic Ocean and Southern Ocean was similar, reaching the lowest value in 2014. By comparing the relationship between SSA concentration, wind speed at 10 m, and sea surface temperature, it was found that sea-air temperature difference might be the main factor affecting the spatial distribution difference of SSA, while sea ice cover and sea surface temperature might be the main factors controlling the interannual variation of SSA in the Arctic Ocean and the Bering Sea, respectively. By comparing the observed SSA concentrations with those simulated by GEOS-Chem, it was found that GEOS-Chem generally underestimated the observed SSA concentrations, especially in the Southern Ocean, by more than 60%. Systematic underestimation in the Southern Ocean was significantly related to sea-air temperature differences. It was suggested that the sea-air temperature difference should be taken into account in the future optimization of models to simulate the SSA in the Southern Ocean.

(2) Based on aerosol samples collected during the Chinese National Arctic Research Expeditions from 2008 to 2016, combined with satellite data of dimethyl sulfur emissions and data processing methods considering air mass history, the interannual variation characteristics and main influencing factors of MSA in the Bering Sea were explored. It was found that the increase in sea surface temperature in the Bering Sea in recent years resulted in an increase in dimethyl sulfur emissions, which led to an increase in MSA concentrations. By further analysis in combination with the backward trajectory of the air mass, it was observed that different sources of the air mass could lead to significant differences in the efficiency of the process of dimethyl sulfur emission to the formation of MSA. When the air mass was mainly from the northwest Pacific Ocean, its atmospheric environment is high O₃, high NO₂, low relative humidity, high temperature, and low cloud liquid water path, which together inhibited the formation of MSA. O₃, temperature and relative humidity were the main factors. When the air mass came mainly from the Arctic Ocean, its atmospheric environment was opposite to that of the northwest Pacific Ocean, which promoted the formation of MSA. These results suggest that air masses from different sources in the Bering Sea can affect the production efficiency of MSA.

(3) Aerosol samples collected during the Chinese National Arctic Research Expeditions from 2010 to 2016 were divided into the Chukchi Sea (CS), the High Arctic Ocean (HAO), and the sea area near Greenland (NG). Combined with the satellite data of dimethyl sulfur emissions and the data processing method considering air mass history, the factors affecting the temporal and spatial distribution of MSA over the Arctic Ocean were investigated. The results showed that the concentration of MSA in CS was mainly affected by long-distance transport from the Bering Sea air mass. In addition, the North Atlantic Oscillation (NAO) can explain the interannual variation in the concentration of MSA in this sea area. The increase in surface temperatures in the Bering Sea and the decrease in rainfall during the long-distance transport of the air mass resulted in a significant increase in the concentration of MSA in the CS in 2016. For the HAO, when the sea ice concentration was between 0.2 and 0.6, high solar radiation may contribute additional sea ice sources of dimethyl sulfur and additional halogen radicals to oxidize dimethyl sulfur, thus promoting the formation of MSA in this area. For NG, the concentration of MSA was influenced by the source, rainfall, and atmospheric chemical processes. This study emphasizes the contribution of atmospheric long-distance transport from the lower latitude Bering Sea to the concentration of MSA in the CS area and the importance of the combined action of sea ice and solar irradiation to the MSA in the HAO area under climate change conditions.

(4) Based on aerosol samples collected during the Chinese National Arctic Research Expeditions from 2010 to 2020, the spatial and temporal distribution characteristics of MSA and non-sea-salt sulfate (nss-SO₄^2-) concentrations over the northwest Pacific Ocean in July and September were investigated. The effect of atmospheric oxidation processes on the ratio of MSA to nss-SO₄^2- was evaluated in conjunction with other environmental satellite data and data processing methods considering air mass history. The results showed that nss-SO₄^2- was mainly contributed by man-made sources in July, while nss-SO₄^2- was mainly contributed by dimethyl sulfur sources in September. Source differences explained most of the temporal and spatial distribution characteristics of MSA and nss-SO₄^2- concentrations. The atmospheric oxidation process was the main factor that caused the difference between the spatial distributions of MSA and nss-SO₄^2- in September. Atmospheric temperature, solar radiation, ozone, and relative humidity affected the atmospheric oxidation process of dimethyl sulfur, and then affected the ratio of MSA to nss-SO₄^2-. Therefore, the ratio of MSA to nss-SO₄^2-- needs to be carefully used to assess the sulfate contribution from dimethyl sulfur sources between different sea areas when the majority of nss-SO₄^2- comes from dimethyl sulfur sources and the net primary productivity is similar across sea areas. In addition, by comparing the mass concentrations of dimethyl sulfur source aerosols and total aerosols, it was found that the contribution of dimethyl sulfur source aerosols to the Northwest Pacific Ocean was not negligible (up to 45%) under the conditions of light winds and high marine net primary productivity.

(5) Based on aerosol samples collected during the Chinese National Antarctic Research Expeditions from 2011 to 2020, the spatial and temporal distribution characteristics of MSA in five regions of the Southern Ocean (Weddell Sea: WS, Indian Ocean: IO, Western Pacific Ocean: WP, Ross Sea: RS, Bellinghausen and Amundsen Sea: B&A) were investigated. Environmental satellite data and data processing methods considering air mass history were combined to explore the main controlling factors of MSA in different sea areas. The results showed that the index of net primary productivity as the source of dimethyl sulfur was the main factor affecting the seasonal variation in MSA between and within sea areas. The MSA concentrations in different areas of the Southern Ocean were affected to different degrees by net primary productivity. The concentrations of MSA in B&A and RS were more affected by net primary productivity than those in WS and IO, but for WP, the concentration of MSA was not related to net primary productivity. This may be because there is little change in net primary productivity in WP. Moreover, the MSA in the WP may be mainly affected by sea level pressure. When sea level pressure is low, more air mass will be gathered, resulting in an increased concentration of MSA. In addition, the contents of dimethyl sulfur source aerosols, organic carbon, and total aerosols were compared. It was found that when the net primary productivity was high, dimethyl sulfur source aerosols were dominant. When the net primary productivity was low, the contribution of organic carbon aerosols to atmospheric aerosols could not be ignored.