2019‒2020 Australian bushfire air particulate pollution and impact on the South Pacific Ocean

Abstract

During late 2019 and early 2020, Australia experienced one of the most active bushfire seasons that advected large emissions over the adjacent ocean. Herein, we present a comprehensive research on mixed atmospheric aerosol particulate pollution emitted by wildfires in the atmosphere and the ocean. Based on a wide range of physical and biochemical data, including the Aerosol Robotic Network, multi-satellite observations, and Argo floats, we investigated the spatio-temporal variations and mixed compositions of aerosol particles, deposition in the coastal waters of eastern Australia and the South Pacific Ocean, and biogeochemical responses in the water column. Four types of wildfire-derived mixed particles were classified by using the optical properties of aerosols into four types, including the background aerosols, mineral dust, wildfire smoke particles, and residual smoke. The coarse particles accounted for more than 60% of the mineral dust on 22 November 2019 in the Tasman Sea; afterwards, during the wildfire smoke episode from December 2019 to January 2020, the particles affected large areas of the atmosphere such as eastern Australia, the South Pacific Ocean, and South America. The maximum value of the aerosol optical depth reached 2.74, and the proportion of fine particles accounted for 98.9% in the smoke episode. Mineral dust and smoke particles from the fire emissions changed the particle composition in the surface ocean. Particle deposition accounted for increases in chlorophyll-a concentration (Chla) standardized anomaly up to maximum of 23.3 with a lag time of less than 8 days. In the vertical direction, float observations showed the impact of exogenous particles on the water column could up to 64.7 m deep, resulting in Chla of 1.85 mg/m3. The high Chla lasted for a minimum period of two months until it returned to normal level.

Australian Bushfires (2019–2020): Aerosol Optical Properties and Radiative Forcing

“…Along with the strong pyrocumulonimbus (pyroCB) convection [23], the emitted BB aerosols managed to reach the higher troposphere and enter into the stratosphere. Compared to a similar extreme event of the North Hemisphere in 2017 (Pacific Northwest Wildfire Event) that injected about 0.1-0.3 Tg of smoke particles into the stratosphere [12,24,25], the impact from the Australian brushfires (2019-2020) was much larger and injected the record amount of 0.4 ± 0.2 Tg in the stratosphere [5,23,26].…”

“…Heinold et al (2021) [67] found values up to +0.50 W/m 2 at the TOA and −0.81 W/m 2 at SRF direct radiative forcing averaged for the Southern Hemisphere during January 2020. Hirsch and Koren (2021) [22] derived a value of +1.10 W/m 2 in the latitude belt between 20 • S and 60 • S. Yu et al (2021) [26] obtained an estimate for global annual average effective RF of −0.03 W/m 2 at TOA and −0.32 W/m 2 at the surface due to the smoke event. According to Chang et al (2021) [67], the wildfire event was associated with a strongly negative RF between −14.80 and −17.7 W/m 2 , which decreased the surface air temperature by about 3.7-4.4 • C.…”

A Study of Two High Intensity Fires across Corsican Shrubland

“…Consequently, the last years have witnessed many high intensity forest fires that have resulted in significant human and economic damages, making them potential catastrophes. For instance, Portugal (2005Portugal ( , 2017, Spain (2017), Greece (2017Greece ( , 2018, Australia (2020), California (2021), and France ( 2022) are examples of places with high intensity forest fire incidents, among a non-exhaustive list [7][8][9][10]. As mentioned above, while climate change affects the frequency and intensity of wildfires, these events contribute themselves to climate change due to carbon emissions.…”

Causes and Effects of the Long‐Range Dispersion of Carbonaceous Aerosols From the 2019–2020 Australian Wildfires

“…Satellite observations have revealed that smoke aerosols emitted from these wildfires were distributed widely across the Pacific Ocean, even reaching South America and the Atlantic Ocean (Hirsch & Koren, 2021; Ohneiser et al., 2020). During the transportation, most aerosols were deposited on downwind landmasses and oceans through dry and wet sedimentation (Li et al., 2021; Pu, Cui, et al., 2021). However, significant amounts of smoke aerosols were injected into the stratosphere, with ∼2.1 Tg being injected over the Southern Hemisphere (SH) in January 2020 alone (Hirsch & Koren, 2021).…”