Problem set · Sharp, Principles of Stable Isotope Geochemistry, 1st ed. (2007) · Answers →
Extensive evaporation takes place in the tropics, and yet the isotopic composition of the tropical oceans is relatively constant. Why?
Denitrification is the process whereby NO3− and NO2− are converted to N2O and, ultimately, to N2 gas by anaerobic bacteria. N2 gas strongly favors the light isotope of nitrogen. If denitrification is most intense in the upper water column, and the resulting N2 gas is lost to the atmosphere, what should the δ15N profile of dissolved NO3− look like?
Figure 5.1 shows a schematic of the effects of various processes on the δ18O and salinity of ocean waters. Explain why the slopes of each curve are different. Justify your explanation.
Why do the Pacific Deep Waters fall below the salinity/δ18O line for surface Pacific waters?
Why do the Antarctic bottom waters plot at higher salinity than those defined by the trend for Atlantic surface waters?
The concentration and δ values for both oxygen and carbon in depth profiles of the ocean are anticorrelated (Fig. 5.5). Why?
Discuss the oxygen isotope composition of the ocean through time, indicating how it might have changed and what evidence is used both for and against your hypothesis. Include the following topics in your discussion: measured δ18O values of ancient sediments, the ocean buffering model of Muehlenbachs and Clayton, and ideas about early ocean formation.
Transcribed from Z. Sharp, Principles of Stable Isotope Geochemistry, 1st ed. (Pearson Prentice Hall, 2007), end-of-chapter problem set (published source). Reference-scale names are written VSMOW, VPDB and VCDT where the original used SMOW, PDB and CDT, with the original numerical constants unchanged; historical usages (e.g. Craig's definition of SMOW) are kept as printed.
The source PDF's text layer scrambles mathematics, so equations and some values were reconstructed during transcription. Bracketed notes and anything tagged reconstructed or check vs print are editorial (constructed), not part of the original, and the warn-tagged items should be verified against the print copy.