Beaufort sea ice loss contributes to enhanced health exposure to fire weather over Southeast Asia

Fires are a major source of air pollutants in Southeast Asia. Over the past few decades, there has been an increase in fire activities in this region, and the causes are not entirely clear. By analyzing multiple observational and reanalysis datasets, as well as conducting climate model simulations, we uncover a distinct positive impact of Arctic sea ice loss on Southeast Asian fire weather. There is a possibility that the fall in the autumn Sea Ice Concentration (SIC) over the Beaufort Sea the year prior contributes to the increase in boreal spring fire activity in Southeast Asia. This sea ice reduction generates a local low warm anomaly, triggering an upper atmosphere Rossby wave train that propagates from the tropical Pacific to Southeast Asia and arrives in Southeast Asia as a high-pressure anomaly with descending air. Moreover, two meridional cells originating from equatorial and polar regions intensify the sinking airflow. This Arctic-driven teleconnection causes high pressure with warmer and dryer surfaces in Southeast Asia, creating favorable conditions for fire ignition and expansion. Based on the fire weather classification criteria, a negative change in SIC of one standard deviation below the climatological mean will expose over 500 million people to very high levels of fire pollution across Southeast Asia, and the number of people exposed to extreme fires will be 1000 times greater than in the present scenario. The above-mentioned mechanism has great implications for projecting decadal air quality and developing relevant health policies to cope with climate change in Southeast Asia.