Impacts of Maritime Continent Deforestation on ENSO Complexity

During the past two decades, the Maritime Continent (MC) has experienced increased deforestation1. Here we show with idealized coupled climate model experiments that deforestation in the MC has the potential to change the complexity (i.e., event-to-event differences) of the El Niño-Southern Oscillation (ENSO) in three key aspects: its spatial pattern, temporal evolution, and amplitude variation. The deforestation alters the relative strengths of the tropical and subtropical types of ENSO dynamics, leading to the changes in ENSO complexity. The strengths of the tropical and subtropical ENSO dynamics are comparable in the control run but the subtropical ENSO dynamics is intensified in the deforestation run. As a result, the deforestation run shows increases in Central Pacific and multi-year La Niñas and re-intensified El Niño events (resembling the 2014-15-16 Super El Niño) compared to the control run. The mechanism for these changes involves an anomalous local overturning circulation over the MC that alters the mean strength of the North Pacific subtropical high resulting in a strengthening of the subtropical ENSO dynamics. The intensified subtropical ENSO dynamics enables a MC-deforested world to produce more complex ENSO events.