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Volcanic eruptions cause sea level spike

Earth/Science Update
The fiercest volcanic eruptions affect global sea level in unexpected ways – at least, in the short term – according to a new study. Particles produced by major eruptions are known to block out sunlight and cool both the ground and the ocean. But computer modellers previously thought this might result in a drop in sea level, since water becomes denser as it cools. In fact, sea levels shoot up after an eruption – initially, at least. Researchers used monthly mean tide-gauge records to determine sea level following five major volcanic eruptions since 1890. They found that sea levels rose by around 9 millimetres following each eruption. This may be because volcanic aerosols reflect sunlight, cooling the ocean surface, which reduces evaporation. "Lower evaporation causes an imbalance in water fluxes to and from the ocean," so that sea levels rise as rivers continue to top up the ocean. Evaporation returns to normal after about a year as the aerosols dissipate and the sea level declines from its peak, continuing to drop to a minimum of about 7 mm below the original level 2 to 3 years after the eruption. The drop is attrbuted to a combination of reduced runoff from the earlier drop in rainfall, reduced glacial melting resulting from the cool spell, and cooler sea water becoming denser.

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