Isoprene and monoterpene emission response to the El Niño-Southern Oscillation

Isoprene and monoterpene emissions from the terrestrial biosphere play a significant role in major atmospheric processes. Such emissions account for 90% of the total volatile organic compound (VOC) emissions and exert a significant influence on the atmosphere's oxidation capacity, aerosol formation and in turn, clouds and climate. Emissions depend on the vegetation response to atmospheric conditions (primarily temperature and light), as well as other stresses e.g. from droughts and herbivory. The El Niño-Southern Oscillation (ENSO) is a natural cycle, arising from sea surface temperature (SST) anomalies in the tropical Pacific, which perturbs the natural seasonality of weather systems on both global and regional scales. Several studies evaluated the sensitivity of BVOC fluxes during ENSO events using transient simulations. While these studies employ realistic scenarios, it is difficult to assess the individual impact of ENSO given multiple forcing on the climate system (e.g. from CO₂, aerosol, etc.). In this work, simulations from a global atmospheric chemistry-climate model with enabled interactive vegetation are used to assess changes in vegetation (net primary production (NPP) and leaf area index (LAI)), meteorology (surface temperature, surface radiation, and precipitation), and consequently, isoprene and monoterpene emission changes attributed to ENSO. Global isoprene emissions could increase by 4% during strong El Niño events with substantial regional changes e.g. + 20% over Amazonia. Changes in isoprene and monoterpene emissions are evaluated in response to meteorological and vegetational variability.