Long-Term Variability in the Arabian Peninsula Droughts Driven by the Atlantic Multidecadal Oscillation

Drought is a recurring hydroclimatic extreme over the Arabian Peninsula (AP). So far, no study has examined the changes in drought characteristics in recent decades, not to mention the background mechanisms for such changes. To this end, analyzing the Standardized Precipitation Evapotranspiration Index (SPEI) mainly from the European Reanalysis (ERA5) data sets, in addition to other observational/reanalysis data sets over the period of 1951-2020, we show that droughts over the AP have increased in frequency and severity over the last two decades. We show that this drought acceleration, which was not observed in the previous 40-50 years, is a combination of decadal variability and long-term trends. Importantly, we demonstrate that the decadal SPEI variability is due to the Atlantic Multidecadal Oscillation (AMO). The unprecedented multiyear drought over the AP in recent decades is evidently associated with the current positive phase of the AMO. We also show that the recent warming of the AP is a more significant factor in the drought intensification than the concurrent weakening of local precipitation. Furthermore, we developed a machine learning model largely based on the observed AMO-SPEI relationship. This model predicts a reduced drought severity over the AP in the near future.