2:15 PM - 2:30 PM
[AAS09-15] Ice nucleating particles over the Arctic Ocean -the importance of bioaerosol-
Keywords:Aerosol, Ice nucleating particle, Bioaerosol, Arctic
Arctic climate change is accelerating at a much faster rate than the global average. Between 1971 and 2017, the Arctic surface air temperature increased by 2.7°C (3.1°C during the cold season and 1.8°C during the warming season) (Box et al., 2019). The effects of Arctic climate change may affect the global climate, a better understanding of Arctic climate change is still required.
Cloud particle formation process is one of the important processes for the Arctic climate, but it still remains a large uncertainty for the Arctic climate prediction. In the temperature range of 0 to -37°C, many cloud particles exist as supercooled liquid droplets, while parts of cloud particles exit as ice particles when solid particles act as ice nucleating particles (INPs). In the Arctic, the temperature can easily decrease to lower than 0°C in the low-level clouds, resulting in mixed cloud formation that contains both droplets and ice particles can be formed. Changes in the balance between ice and water in the cloud affect climate through changes in the radiative property and life-cycle of clouds, research for the Arctic INP (such as particle identification, micro-physicochemical particle feature, and the process of INP production and their transport) are highly important. However, knowledge of the Arctic INP, especially over the Arctic Ocean, is still poor, more Arctic INP researches are required. In 2022, we conducted online aerosol observations and samplings on the Arctic Ocean. Here, we will report and discuss the result of individual particle analysis for Arctic INP with the results of online observations.
Observation was conducted in August and September 2022, during the Arctic cruise (MR2206C) by Mirai (research vessel of JAMSTEC). As online observations, size distributions of coarse particles (KR-12A, Rion) and fine particles (Nano Scan model 3910, TSI) and fluorescence particle concentration (WIBS-4A, DMT) were observed. On the compass deck, we conducted aerosol samplings using a 1-stage impactor with quartz fiber filters equipped with a high-volume air sampler (HV-700F, SIBATA) for chemical analysis and total particle sampling by poly-carbonate filter (47mm in diameter and 0.2 µm in pore size, Whatman) for INP concentration analysis every 2 days. And more, we collected aerosol particles on EM grids (U1007, EM Japan) using a 3-stage impactor (MPS-3, California Measurements) for individual INP analysis (samples sized >2µm and 0.3-2µm were used). Individual INPs which can form ice crystals at temperatures above -32°C were identified using an optical microscope (Axio imager M2m, Zeiss) system coupled with a cool chamber (10002L, LINKAM) at the Meteorological Research Institute. Then, using a scanning electron microscope (Quanta 450 FEF, FEI) with an energy-dispersed spectrometer (EDS; Octan Elite30, EDAX), physicochemical particle features of individual INPs were analysed. In addition, parts of fine-stage EM samples (0.05-0.3µm) were analysed by a transmission electron microscope with an EDS (EDAX EDS, EDAX) for mixing state and particle features of fine particles.
We observed an enhancement of fluorescence particle concentrations off the coast of Canada. During this period, the number fractions of bioaerosols increased in collected aerosol particles. From individual INP analysis, bioaerosols also accounted for a large fraction of INPs, indicating the significant injection of bioaerosols into the Arctic Oceans and its impacts on the existing INPs. From back trajectory analysis, terrestrial impacts on observed airmasses were indicated, on the other hand, a significant injection of river water to the surface seawater was also observed. Now, we continue to analyse the airmass origin to understand the origin of observed bioaerosols. In this presentation, we will report on the relationship between the Arctic bioaerosol and INPs.
Cloud particle formation process is one of the important processes for the Arctic climate, but it still remains a large uncertainty for the Arctic climate prediction. In the temperature range of 0 to -37°C, many cloud particles exist as supercooled liquid droplets, while parts of cloud particles exit as ice particles when solid particles act as ice nucleating particles (INPs). In the Arctic, the temperature can easily decrease to lower than 0°C in the low-level clouds, resulting in mixed cloud formation that contains both droplets and ice particles can be formed. Changes in the balance between ice and water in the cloud affect climate through changes in the radiative property and life-cycle of clouds, research for the Arctic INP (such as particle identification, micro-physicochemical particle feature, and the process of INP production and their transport) are highly important. However, knowledge of the Arctic INP, especially over the Arctic Ocean, is still poor, more Arctic INP researches are required. In 2022, we conducted online aerosol observations and samplings on the Arctic Ocean. Here, we will report and discuss the result of individual particle analysis for Arctic INP with the results of online observations.
Observation was conducted in August and September 2022, during the Arctic cruise (MR2206C) by Mirai (research vessel of JAMSTEC). As online observations, size distributions of coarse particles (KR-12A, Rion) and fine particles (Nano Scan model 3910, TSI) and fluorescence particle concentration (WIBS-4A, DMT) were observed. On the compass deck, we conducted aerosol samplings using a 1-stage impactor with quartz fiber filters equipped with a high-volume air sampler (HV-700F, SIBATA) for chemical analysis and total particle sampling by poly-carbonate filter (47mm in diameter and 0.2 µm in pore size, Whatman) for INP concentration analysis every 2 days. And more, we collected aerosol particles on EM grids (U1007, EM Japan) using a 3-stage impactor (MPS-3, California Measurements) for individual INP analysis (samples sized >2µm and 0.3-2µm were used). Individual INPs which can form ice crystals at temperatures above -32°C were identified using an optical microscope (Axio imager M2m, Zeiss) system coupled with a cool chamber (10002L, LINKAM) at the Meteorological Research Institute. Then, using a scanning electron microscope (Quanta 450 FEF, FEI) with an energy-dispersed spectrometer (EDS; Octan Elite30, EDAX), physicochemical particle features of individual INPs were analysed. In addition, parts of fine-stage EM samples (0.05-0.3µm) were analysed by a transmission electron microscope with an EDS (EDAX EDS, EDAX) for mixing state and particle features of fine particles.
We observed an enhancement of fluorescence particle concentrations off the coast of Canada. During this period, the number fractions of bioaerosols increased in collected aerosol particles. From individual INP analysis, bioaerosols also accounted for a large fraction of INPs, indicating the significant injection of bioaerosols into the Arctic Oceans and its impacts on the existing INPs. From back trajectory analysis, terrestrial impacts on observed airmasses were indicated, on the other hand, a significant injection of river water to the surface seawater was also observed. Now, we continue to analyse the airmass origin to understand the origin of observed bioaerosols. In this presentation, we will report on the relationship between the Arctic bioaerosol and INPs.