| Summary: | The Arctic is experiencing surface warming rates that exceed those observed at lower latitudes. This is caused by a complex system of feedback mechanisms in the Arctic climate system and is referred to as Arctic Amplification. Persistent mixed-phase clouds cover large areas of the Arctic region and thus, have a substantial impact on the radiative budget in the Arctic. One consequence of the amplified warming is that Arctic sea-ice extent has been decreasing over the past decades. With the rapid decline in sea-ice extent, shipping activity is projected to significantly increase due to easier accessibility and availability of shorter transportation routes. Ships are also a significant source of atmospheric pollutants, which include greenhouse gases, sulfur oxides (SOx) and particulate matter (PM). Increased local emissions of such pollutants may perturb the natural state of Arctic clouds and thus, can lead to further climatic feedbacks. Simultaneous with climate change, the shipping sector is undergoing regulatory changes aimed at reducing exhaust emissions of climate- and health-affecting substances. SOx and PM emissions have been strongly linked to tens of thousands of premature deaths worldwide. As a result, the International Maritime Organization (IMO) implemented regulations that aim to reduce emissions of SOx and indirectly, of PM to atmosphere. Respective IMO regulations mandate ships to either use fuels with reduced fuel sulfur content (FSC) or to use exhaust aftertreatment systems, such as wet scrubbers, in instances where ships continue to utilize non-compliant high sulfur content fuels. Both, FSC reduction and exhaust wet scrubbing change physicochemical properties of exhaust particles and may therefore, lead to climate feedbacks. A series of laboratory engine experiments were performed to characterize impacts of FSC reduction and exhaust wet scrubbing on the physicochemical properties of exhaust particles. The secondary impact of compliance choices on exhaust particles’ cloud activity, including liquid ...
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