Significant decadal-scale impact of volcanic eruptions on sea level and ocean heat content

Ocean thermal expansion contributes significantly to sea-level variability and rise1. However, observed decadal variability in ocean heat content2,3 and sea level4 has not been reproduced well in climate models5. Aerosols injected into the stratosphere during volcanic eruptions scatter incoming solar radiation, and cause a rapid cooling of the atmosphere6,7 and a reduction in rainfall6,8,9, as well as other changes in the climate system7. Here we use observations of ocean heat content2,3 and a set of climate simulations to show that large volcanic eruptions result in rapid reductions in ocean heat content and global mean sea level. For the Mt Pinatubo eruption, we estimate a reduction in ocean heat content of about 3 × 1022 J and a global sea-level fall of about 5 mm. Over the three years following such an eruption, we estimate a decrease in evaporation of up to 0.1 mm d-1, comparable to observed changes in mean land precipitation6,8,9. The recovery of sea level following the Mt Pinatubo eruption in 1991 explains about half of the difference between the long-term rate of sea-level rise4 of 1.8 mm yr-1 (for 1950–2000), and the higher rate estimated for the more recent period where satellite altimeter data are available (1993–2000)4,10.