Storylines of Maritime Continent dry period precipitation changes under global warming

Abstract

The dry half of the year from May to October over the Maritime continent (MC) has experienced unprecedented damages from forest fires in recent decades. The observed interannual rainfall variability during this period is closely tied to sea surface temperature (SST) variability over the equatorial Pacific (EP). Therefore, the future evolution of EP SST can be expected to influence the climatological precipitation over the MC. Whilst multi-model means suggest a future drying trend over the south-western part of the MC, there is considerable model uncertainty. Here, using a storyline approach with the 38 climate models from Coupled Model Intercomparison Project phase 6 (CMIP6), we distinguish the model uncertainty associated with changes in the zonal EP SST gradient from that associated with the basin-wide EP warming. We find that an increase in east-to-west EP SST gradient would bring more rainfall over the north-eastern regions including northern Borneo, Sulawesi and New Guinea. In contrast, the intensity of the basin-wide warming of EP SST is directly linked with the drying response seen over the south-western MC in the multi-model mean. This drying affects the highly vulnerable regions of Sumatra and Kalimantan for forest fires. Our results suggest that a storyline under higher basin-wide EP warming accompanied by an El-Niño like change in zonal SST gradient would lead to even drier climatic conditions over these key regions. However, the observed record of more than one hundred years favours a storyline of lower basin-wide EP warming accompanied by a La-Niña like change in zonal SST gradient, which would lead to minimal drying over the south-western MC and wetter conditions over the north-eastern parts of the MC.