Seafloor volcano pulses may help trigger natural climate swings

A new study has recently revealed that seafloor volcano pulses may alter climate.

Vast ranges of volcanoes hidden under the oceans are presumed by scientists to be the gentle giants of the planet, oozing lava at slow, steady rates along mid-ocean ridges. But a new study shows that they flare up on strikingly regular cycles, ranging from two weeks to 100,000 years and, that they erupt almost exclusively during the first six months of each year.

The pulses, apparently tied to short- and long-term changes in earth's orbit, and to sea levels, might help trigger natural climate swings. Scientists have already speculated that volcanic cycles on land emitting large amounts of carbon dioxide might influence climate; but up to now there was no evidence from submarine volcanoes.

The findings suggested that models of earth's natural climate dynamics, and by extension human-influenced climate change, may have to be adjusted.

That has been a mystery, partly because undersea eruptions are almost impossible to observe. However, Maya Tolstoy of Columbia University's Lamont-Doherty Earth Observatory and other researchers recently have been able to closely monitor 10 submarine eruption sites using sensitive new seismic instruments. They have also produced new high-resolution maps showing outlines of past lava flow.

Tolstoy analyzed some 25 years of seismic data from ridges in the Pacific, Atlantic and Arctic oceans, plus maps showing past activity in the south Pacific.

Volcanically active mid-ocean ridges crisscross earth's seafloors like stitching on a baseball, stretching some 37,000 miles. They are the growing edges of giant tectonic plates; as lavas push out, they form new areas of seafloor, which comprise some 80 percent of the planet's crust.

Daniel Fornari, a senior scientist at Woods Hole Oceanographic Institution not involved in the research, called the study "a very important contribution." He said it was unclear whether the contemporary seismic measurements signal actual lava flows or just seafloor rumbles and cracking. But, he said, the study "clearly could have important implications for better quantifying and characterizing our assessment of climate variations over decadal to tens to hundreds of thousands of years cycles."

The study is published in the journal Geophysical Research Letters.