Meteorological export and deposition fluxes of black carbon on glaciers of the central Chilean Andes

Abstract

Abstract. Air pollution in the central zone of Chile is not only a public health concern but also threatens water resources and climate, in connection with the transport and deposition of black carbon (BC) from urban centers onto the glaciers of the Andes. Chemistry-transport simulations reveal a seasonal dichotomy in the flux and latitudinal pattern of BC deposition on glaciers of the central Chilean Andes. The average deposition flux of BC on glaciers between 30 and 37∘ S is 4 times larger in winter, affecting mostly low-elevation glaciers, whereas the smaller summertime flux affects glaciers evenly, irrespective of their elevation. The contribution of emissions from the city of Santiago is dominant in summertime with more than 50 % along the Andes but minor in wintertime with less than 20 % even close to the capital city. Transport at larger scales and more local sources likely account for the remaining flux. The superimposition of synoptic-scale circulation and local mountain-valley circulation along the Andes drives the differences between summertime and wintertime deposition fluxes and generates a greater meteorological export potential during summer months. Future emissions and climate projections suggest that under the RCP8.5 scenario the gap between summertime and wintertime BC export and deposition flux could decrease, thereby pointing to summertime emission control gaining relevance. The chemistry-transport modeling approach for BC deposition on the Andes sheds light on the importance of the often disregarded summertime emissions on the radiative balance of its glaciers, particularly in the vicinity of Santiago.

The CHIMERE chemistry-transport model v2023r1

“…This framework is well suited to include emissions due to volcanic eruptions or industrial accidents for example (e.g. Lachatre et al (2022)), but also to study the behaviour and motion of air masses to and from key areas such as cities or mountain valleys (Lapere et al, 2023;Deroubaix et al, 2019). Lachatre et al (2022) shows an example of a real species (SO 2 ) emitted as a tracer over a specific point, along with its normal surfacic anthropogenic emissions from emisurf.…”

Changes in South American Surface Ozone Trends: Exploring the Influences of Precursors and Extreme Events

“…South America (10°N to 55°S) encompasses tropical, subtropical and midlatitude climates, in addition to high-altitude conditions within the Andes Mountain range (Garreaud et al, 2009). This continent also hosts essential ecosystems for global water and carbon cycles, including tropical and subtropical wetlands, Andean glaciers, the Amazon rainforest and peatlands in Patagonia (Gumbricht et al, 2017;Hoyos-Santillan et al, 2019;Heinrich et al, 2021;Lapere et al, 2023;Molina et al, 2015). In contrast, 85% of the continent's population, estimated at more than 430 million people in 2022, resides in urban areas (Population Reference Bureau 2024).…”