Trans-Pacific transport of aerosols — North America gets an equal load of overseas aerosols as domestically emitted
Do you fly across continents? Are you fond of imported goods? Apparently, passengers and commercial goods are not the only ones making intercontinental transits. Aerosols, or tiny particles suspended in the air, are also imported from other parts of the globe through air currents across the oceans. These aerosols include desert dust and combustion aerosols derived from biomass and fossil fuels.
A new study published in the current issue of Science used satellite measurements to estimate the types and distribution of aerosols across the Pacific Ocean. The study reports that a significant amount of aerosols gets blown across the Pacific and transported to North America. The estimated domestic annual emission of aerosols in North America totals 69Tg (teragram, or 1012 grams). On top of that, about 60Tg of aerosols are annually imported via trans-Pacific transport, nearly equalling the amount produced domestically. Think about it this way: this is almost equivalent to 60 million heavy-weight trucks weighing 6 tons (or 6,000kg) each being thrown across the Pacific and landing on North America every year!!
The majority of trans-Pacific transport of aerosols originates from Asia, but significant amount is also transported from as far as Africa, Middle East, and Europe. Approximately 93% of the annually imported aerosols are dust. Therefore, the authors of the study caution that in addition to controlling air pollutants emitted from factories and vehicles, preventing desertification is important in reducing transport of dust aerosols.
What are the impacts of extra aerosols above North America? The aerosols can break the natural balance in the atmosphere by interfering with solar radiation and radiation re-emitted from the Earth. In addition, it may have an impact on the regional climate, as aerosols can act as ice nuclei and alter cloud and precipitation processes. They can also accelerate melting of the snow by depositing on the snow. Furthermore, dust aerosols can have an impact on the air quality. Nonetheless, the authors of the study note that this may not be as big an impact compared to domestic aerosols. This is because imported aerosols are mainly high up in the atmosphere – anything that is lower gets eliminated during the transport – while domestic dust aerosols reside near the surface and affect the air quality.
I hope that the reader’s response to the report is not to blame other countries for pollution but, instead, realize that we are in this together and what we do affect the other. With that, I am going to close this post with a concluding remark from the study:
“Although this study focuses on the impacts of intercontinental transport into North America, aerosols emitted and produced in North America also affect other regions via intercontinental transport. To mitigate aerosol impacts on regional climate change, actions by a single nation are inadequate. The world must work cooperatively and act synchronically to meet the challenges of global health on a changing planet.” (Hongbin Yu et al., 2012)
Thank you for reading the post, and see you next week 🙂