Publication Date

2009-07-16

Availability

Open access

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Marine and Atmospheric Chemistry (Marine)

Date of Defense

2008-11-19

First Committee Member

Frank J. Millero - Committee Chair

Second Committee Member

Dennis A. Hansell - Committee Member

Third Committee Member

Rana A. Fine - Committee Member

Fourth Committee Member

Rik Wanninkhof - Outside Committee Member

Abstract

Since the industrial revolution, CO sub 2 has increased in the atmosphere and about 40% of the increase has been taken up by the ocean. An artifact of increasing CO sub 2 in the ocean is ocean acidification; it changes the calcium carbonate saturation state, which in turn alters the calcification rate of shelled organisms. The purpose of this dissertation is to estimate the changes in the carbonate system in the oceans, and whether these changes are due to natural (biological activity, chemical transformation or mixing of water masses) or anthropogenic (human activities) perturbations. The first hypothesis states that the presence of boric acid (B(OH) sub 3) in seawater changes the thermodynamic constants of CO sub 2, pK sup * sup 1 and pKsup * sup 2. Due to experimental limitations, the solubility of B(OH) sub 3 was determined in electrolyte solutions (LiCl, NaCl, KCl, RbCl and CsCl) instead of real or artificial seawater. The results can be used to estimate the B(OH) sub 3 activity coefficients gamma sub B and solubility [B] in natural mixed electrolyte solutions. The second hypothesis states that filtering seawater sampled in the open ocean is necessary for the determination of total alkalinity (TA). Measurement of 180 samples of surface, oxygen minimum, and deep waters in the Pacific and Indian oceans revealed that the at- sea measured TA of filtered and unfiltered samples were not statistically different. Finally, a synthesis and analysis of the carbonate parameters in the Atlantic and Indian oceans is undertaken. Results from repeat hydrographic cruises in these oceans were used for this task. Parameters TA and total CO sub 2 (TCO sub 2) are predicted using hydrographic properties and a multi-linear regression method to obtain a more homogenous dataset. The results of the predicted TA prove to be successful, which is not the case for TCO sub 2 at the surface of the ocean. Finally, it is found that the increase in anthropogenic CO sub 2 signal remineralization and mixing of water masses increase the acidity of the ocean at the surface and in deep waters, respectively. This causes the aragonite saturation horizon to shoal. Recommendations for further studies are provided in the "Summary and conclusion" chapter.

Keywords

Ocean Acidification; Carbonate System; Marine CO Sub 2

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