Collaborative Research: Development of an in situ sensor for high-resolution measurements of total dissolved inorganic carbon

Sri International, Menlo Park CA

Investigators

Abstract

It has become increasingly clear that the impact of anthropogenic CO2 on the global oceans may have severe consequences to a wide variety of organisms and food webs. Reduced pH and carbonate saturation states have been shown to cause reduction in calcification rates in aragonite producing corals and pteropods. Recent investigations indicate that the aragonite saturation horizon in the North Pacific has measurably shoaled in the last two decades. Because the effects of increasing atmospheric CO2 can affect all aquatic systems, studies must be conducted as synoptically as possible. This can be most effectively accomplished through the wide-scale use of in situ sensors Investigations into carbon system dynamics are seriously hampered by the inability to measure total dissolved inorganic carbon (CT) in situ. While the capabilities exist to measure pH, CO2 fugacity (f CO2), and pCO2 in situ, such parameters strongly co-vary and therefore carbon system parameters derived from these values are subject to much greater error than those calculated using one of those terms and either total alkalinity (AT) or CT. The proposed work builds on the decade-long development and deployment of the in situ Spectrophotometric Elemental Analysis System (SEAS), as well as the development and field testing of the bench-top MICA (Multiparameter Inorganic Carbon Analyzer). The project will involve development of a total carbon capability on the SEAS platform through modeling, design, and lab tests of a new optical cell; configuring and calibrating SEAS for CT measurements; and field testing/ground truthing in a local harbor. The PI's request funding to: (1) Develop, test, and refine an optical cell that will facilitate measurements of dissolved inorganic carbon (DIC) in situ; (2) conduct a series of laboratory tests to optimize the CT method for use on the SEAS instrument; and (3) conduct field tests using SEAS-CT and SEAS-pH instruments at Bayboro Harbor. While the objective of the proposed work is to develop an in situ instrument capable of performing CT measurements in a moored configuration, equilibration on the scale of two minutes should allow the development of an in situ profiling capability as long as the profiling rate is sufficiently slow. Broader Impacts: To be able to use in situ platforms will enhance the regional and global understanding of relevant environmental issues related to climate (air-sea exchange of CO2 and the ocean's role in the atmospheric uptake) as well as the effect of the increased CO2 in the ocean such as ocean acidification. Good including graduate. The proposed activity will contribute to the advance of knowledge through the mentoring of undergraduate and graduate students, which is clearly effective since the Principal Investigator was herself a graduate student in this group. A minority graduate student involved in the Bridge to the Doctorate program will also participate to the project. The proposal has huge potential for broader community collaboration and the proposers give examples of recent partnerships. This will be of great benefit for society since the fate of anthropogenic carbon can then be better predicted for future scenarios of various CO2 emissions, which will directly influence the decision on climate mitigation strategies.