London, Nov 28: A new study has found out that volcanic eruptions might lead to an increase in global sea level.

The study points out that the eruptions might also affect the sea level in unexpected ways, like blocking out sunlight and cooling both the ground and the ocean.

Computer modellers previously thought that this might result in a drop in sea level, since water becomes denser as it cools.

But the research work by Aslak Grinsted of the University of Lapland in Finland and colleagues, indicates that sea levels shoot up after an eruption, initially at least.

The researchers used monthly mean tide-gauge records to determine sea level following five major volcanic eruptions since 1890, adjusting to remove changes in local elevation and atmospheric pressure.

They found that sea levels rose by around 9 millimetres following each eruption.

Aslak Grinsted suggest that this is 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," Grinstead told New Scientist. "So, sea levels rise as rivers continue to top up the ocean," he added.

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.

Grinsted attributes the drop 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. (ANI)