Systematic Change in Global Patterns of Streamflow Following Volcanic Eruptions

Abstract:

Precipitation decreases over much of the globe following large explosive volcanic eruptions, particularly in climatologically wet regions. Stratospheric volcanic aerosols reflect sunlight, reducing evaporation, whilst surface cooling stabilises the atmosphere and reduces its water-holding capacity. Circulation changes modulate this global precipitation reduction on regional scales. Despite the importance of rivers to people, it has until now been unclear whether volcanism causes detectable changes in streamflow given large natural variability. Here we analyse the response of 50 major world rivers using observational records, averaging across multiple eruptions to reduce noise. We find statistically significant reductions in flow for the Amazon, Congo, Nile, Orange, Ob, Yenisey and Kolyma amongst others. Results are clearer when neighbouring rivers are combined into regions based on the areas where climate models simulate either an increase or a decrease in precipitation following eruptions. We detect a significant streamflow decrease (p<0.1) in northern South American, central African and high-latitude Asian rivers, and on average across wet tropical and subtropical regions. We also detect a significant increase in southern South American and SW North American rivers. This significant change in global scale streamflow following volcanic eruptions has implications for predicting and mitigating the effects of future eruptions.