Lecture 20

Lecture 20 - SIO 40 Life and Climate on Earth Nov 18 2009...

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Unformatted text preview: SIO 40 Life and Climate on Earth Nov 18 2009 Lecture 20 - Ocean Acidification and Warming polar pteropod cold-water coral Observed and expected ocean climate change The oceans climate will be altered in important ways by the large-scale increases in CO 2 in the atmosphere as a result of human activities. The oceans heat content will rise significantly as waters warm up. In addition, as the ocean takes up more and more CO 2 from the atmosphere, seawater pH will decrease. Recommended background reading, posted as pdf on class website Article from Scientific American , 2006 e know that CO 2 is increasing in the atmosphere.. Where else is anthropogenic CO 2 accumulating? The oceans have absorbed about 40% of the CO 2 emitted by fossil fuel burning since pre-industrial times. hile we see fossil-fuel CO 2 accumulating in all ocean surface waters, penetration is especially deep in the North Atlantic because this is a region of deep water formation. Vertical inventory of anthropogenic CO 2 in the ocean An alternative view confirms the high inventory of anthropogenic CO 2 in the North Atlantic. The net result of oceanic CO 2 uptake is an increase in H + (ie. acidity) and decrease in CO 3 2- . Increasing CO 2 , decreasing pH observed at ocean time series stations Several decades of observations at different ocean time series stations (BATS is near Bermuda, HOT is near Hawaii, ESTOC is near the Canary Islands) confirms a trend of increasing CO 2 concentrations in surface waters (expressed above as the partial pressure of CO 2 , pCO 2 ) and decreasing pH. Estimated change in surface ocean pH from pre-industrial to modern times As expected, there is a correspondence between areas with the greatest CO 2 uptake (see slide #6) and areas of the greatest decrease in surface ocean pH. Projected changes in ocean surface pH for various emission scenarios With the A1B emissions scenario, average global ocean surface pH is projected to drop from values of about 8.1 to7.85 by 2100. This graph shows changes in surface pH, which is most sensitive, but over time pH will be affected over the full depth of the oceans. Modern-day surface ocean pH lthough the projected drop in pH is relatively small in terms of an absolute amount change on the full pH...
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Lecture 20 - SIO 40 Life and Climate on Earth Nov 18 2009...

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