Increased Ocean Silica May Be Delaying Global Warming
EarthVision Environmental News
06/28/00
CHESTNUT HILL, MA, June 28, 2000 - The ocean may be removing large amounts of carbon dioxide (CO2) from the atmosphere and delaying global warming according to a Boston College Geologist's "Silica Hypothesis." Boston College's Kevin Harrison, writing in the June issue of
Paleoceanography, says his hypothesis could explain the 30 percent drop in atmospheric carbon dioxide levels during glacial times
What lies at the heart of the hypothesis is the amount of dust reaching the oceans. According to Harrison, human activity has doubled the amount of dust delivered to the oceans - dust that contains silica. Some of this silica then becomes available for biological uptake. Harrison postulates that in glacial times, the increased silica levels brought about a concurrent rise in diatoms and a decrease in coccoliths. Diatoms are single-celled, microscopic plants that have silica skeletons, while the coccoliths have external calcified plates. According to Harrison, this shift increased the ability of the ocean to remove carbon dioxide from the atmosphere - decreasing the population of coccoliths decreased the flux of calcite to the sediments, which in turn lowered CO2 levels.
Harrison's model estimates that a seven-fold increase in dustiness would have lowered carbon dioxide levels from 280 ppm to 200 ppm - enough to explain the observed glacial-interglacial CO2 transition. Organic biomarkers in the sedimentary record support Harrison's hypothesis.
Harrison notes that present-day increases in dust level suggest that the same diatom-based mechanism may be at work today, removing significant amounts of carbon dioxide from the atmosphere and slowing the rate of global warming.
For the full text of this article, entitled "Role of increased marine silica input on paleo-CO2 levels," see the June 2000 issue of Paleoceanography, (Vol. 15, No. 3, pp. 292-298).