Measured and Estimated pH Change and Trends Throughout the Southern Ocean, 1972-2011

• Main Author: Margolin, Andrew Reynolds
• Format: Text
• Language: unknown
• Published: CU Scholar 2012
• Subjects: Chemistry and Biochemistry; Southern Ocean
• Online Access: https://scholar.colorado.edu/honr_theses/261; https://scholar.colorado.edu/cgi/viewcontent.cgi?article=1456&context=honr_theses

Recent studies have shown that the Southern Ocean is experiencing changes in its carbon chemistry due to the uptake of anthropogenic CO2 from the atmosphere, a process that lowers the pH (Sabineet al., 2004). These changes have reduced the surface carbonate concentration of the Southern Ocean by more than 10% when compared to preindustrial levels (Orr et al., 2005). Here, we have used total alkalinity, dissolved inorganic carbon, and the partial pressure of CO2 in seawater to quantify the change of pH throughout the Southern Ocean. We calculated pH at every location where two of the parameters were measured on over sixty hydrographic cruises, and created an array of new pH data. We were able to calculate over 41 thousand pH data points, resulting in a grand total of 73,477 calculated and measured pH values for our analysis. Profiles of decadal pH change from multiple repeat cruises were used to determine focus regions where pH change was most dramatic for further trend analysis. Using measurements from the 1990s to the present day we examined the vertical and spatial heterogeneity in pH trend patterns, and commented on the statistical significance of pH trends. We have determined that pH has significantly changed in the top 1 km of the water column throughout the Southern Ocean by −0.03 ± 0.03 pH units. Implications of these results will be used to assess carbon-climate model performance.