Volcanic eruptions raise global sea level

27.11.2007 9:00
Major volcanic eruption’s effect on the global water cycle and sea level changes equal to El Niño’s, researchers say.

Large volcanic eruptions inject aerosols into the stratosphere, and these
aerosols reflect sunlight causing global dimming and thus lower temperatures
at the earth surface. The cooling of the ocean surface causes less
evaporation. As water flux from terrestrial reservoirs and river discharge
continue, the reduced evaporation leads to a global sea level rise of 6-12
millimeters during the first year following an eruption.

This results from research by Professor John Moore, Dr. Aslak Grinsted and
Dr. Svetlana Jevrejeva, published in Proceedings of the National Academy of
Sciences of the United States of America, November 26-30, 2007.

After approximately one year, stratospheric aerosols have been removed and
evaporation reaches normal values. However, now the river discharge is
reduced due to the low precipitation in the preceding year and sea level
therefore drops by 4-10 millimeters 2-3 years after the eruption.

The magnitude of this phenomena is similar to the impact of  El Niño -
Southern Oscillation, which causes heavy rainfall in Americas, drought in
the eastern Pacific and global changes in weather.

To quantify the impact of eruptions, Prof. Moore, Dr. Grinsted and Dr.
Jevrejeva used records from 830 tide gauges across the globe, and five major
eruptions between 1890 and  the Pinatubo eruption of 1991. The effects of
climate change and other disturbances such as earthquakes and uneven
distribution of tide gauges were eliminated from the data by using novel
statistics.

No other previous sea level reconstruction has been accurate enough to show
either drop or rise caused by volcanic eruptions. Climate models have only
showed the drop.

For more information, please contact:
Research Professor John Moore, Arctic Centre, University of Lapland,
Finland
Mobile: +358 400194850
Email: john.moore (at) ulapland.fi

Researcher, Dr. Aslak Grinsted Arctic Centre, University of Lapland, Finland
Mobile: +358 405121481
Email: aslak.grinsted (at) ulapland.fi

www.arcticcentre.org