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The Future of Arctic Aerosols: Despite a downward trend in anthropogenic aerosol concentrations in the Arctic, aerosols will continue to have significant climate forcing effects in the region for years to come

Research output: Book/anthology/dissertation/reportPh.D. thesis

  • Daniel Charles Thomas
The Arctic is an area of particular interest in the field of atmospheric science, owing to the amplified warming observed relative to the global mean, and the impact this will have on the global environment. Contributing factors to Arctic climate forcing that are not yet well understood include the dynamics and impacts of aerosols. Long-range transported anthropogenic aerosols dominate the population during the winter, and more locally produced biogenic aerosols dominate during the summer. It is well established that anthropogenic aerosols, specifically those containing sulphate and black carbon (BC), typically scatter and absorb light more strongly than smaller, biogenic aerosols. The concentrations of these species have also declined in recent years. This thesis addresses the fact that despite these observations, aerosols will most likely continue to have a significant climate-forcing effect in the Arctic in the following decades. Firstly, a trend analysis of physical aerosol properties and air mass history was performed for an aerosol number concentration dataset from Villum between the years 2010 and 2018. This showed an increasing trend in the concentrations of ultrafine mode aerosols, and specifically biogenic aerosols from new particle formation processes, which is attributed to changing transport patterns. A separate study into the optical properties and direct radiative forcing potential of these aerosols showed that these same biogenic aerosols are in fact capable of interacting with a significant amount of sunlight over the course of a year. This is because they are predominantly present in the atmosphere during the summer, when the Arctic experiences polar day. A study was also carried out investigating the response of Arctic BC concentrations to the COVID-19 lockdown of spring/summer 2020, as a case study for extreme global emission changes. It was found that despite severe cuts in emission sources like road traffic and aviation, only a reduction in Arctic BC of around 10% was predicted by the model DEHM, and the change could not be detected by BC measurements at Villum. Between these studies and the knowledge that melting Arctic sea ice could lead to new trans-Arctic shipping routes by mid-century, thereby emitting anthropogenic aerosols directly into the Arctic environment, it is evident that the climate impact of aerosols in the Arctic will continue through this century. It is therefore vital that we continue to expand and develop Arctic aerosol measurements. A key element that will further our understanding of the Arctic atmosphere is the in situ measurement of atmospheric vertical profiles, using platforms such as unmanned aerial vehicles, manned aircraft or balloons. The fourth and final study in this thesis uses a newly developed manned aircraft system equipped with instruments to measure aerosol physical properties in the Greater Copenhagen area, and the results are compared with the model DEHM. The system is proven to produce valuable vertical profile data of aerosol parameters, and it therefore has immense potential to be used for similar campaigns in the Arctic.
Original languageEnglish
PublisherAarhus Universitet
Publication statusPublished - Mar 2023

Note re. dissertation

Termination date: 03.03.2023

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ID: 293804469