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Roberta in Thailand Roberta C. Hamme

Associate Professor
Canada Research Chair in Ocean Carbon Dynamics
School of Earth and Ocean Sciences
University of Victoria

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Understanding what drives the cycles of gases like carbon dioxide and oxygen is essential to understanding our changing planet. I measure a suite of inert and bioactive gases, like argon and oxygen, to investigate oceanic processes. Dissolved inert gases can tell us about how gases move between the atmosphere and the ocean and what processes drive those fluxes, such as rapid cooling and bubbles created by breaking waves. Dissolved oxygen measurements indicate the productivity of ocean waters. Atmospheric measurements can give us a globally integrated picture of the ocean uptake or release of gases. These different approaches allow my group to investigate a large variety of processes across many spatial and temporal scales.

Prospective Students: I am seeking motivated MSc and PhD students to join my chemical oceanography group. Possible scientific research directions include quantifying denitrification through measurements of dissolved N2/Ar ratios and quantifying biological productivity rates using oxygen sensors on profiling floats.
Denitrification and related processes remove bioavailable nitrogen from the ocean, transforming it into N2 gas. This process happens only in oxygen deficient zones of the ocean, which have recently been expanding. This has the potential to reduce the total amount of bioavailable nitrogen in the ocean, and hence affect productivity rates and atmospheric carbon dioxide levels. We are focusing our most recent efforts on the Arctic, where denitrification rates are poorly known. Recent data suggests that we need to collect samples in the Chukchi Sea to accurately measure denitrification in that region. We also have preliminary data from Baffin Bay showing unusually high N2 values that we wish to investigate further.
Photosynthesis and the subsequent export of organic carbon from the surface ocean profoundly lowers atmospheric carbon dioxide levels. Our lab has developed high precision methods based on O2/Ar ratios to quantify these export rates. We wish to expand oxygen-based estimates of productivity to use data from oxygen sensors carried on profiling Argo floats, in order to collect this type of data on greater spatial and temporal scales than possible from ships. This project will focus on developing techniques for floats in the subarctic NE Pacific and will compare float measurements to our lab's measurements based on discrete samples.
Any of the projects in my lab would require a student to periodically go to sea to collect dissolved gas samples and then analyze the samples in my laboratory using cryogenic gas processing techniques and a mass spectrometer. While I would expect to train any student in the necessary procedures, it is important that the student possess a strong attention to detail and good analytical chemistry skills. Prospective students should be bright and self-motivated with good communication skills, a natural curiosity about science, and some patience for lab work.

The Download page contains both dissolved gas databases from my published papers and MatLab scripts for gas solubility and other useful seawater related quantities. I invite collaboration with people interested in using these gases as tracers, particularly modelers.


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School of Earth and Ocean Sciences
University of Victoria
P.O. Box 1700 STN CSC
Victoria, BC V8W 2Y2
CANADA
Courier address


(250) 472-4014
FAX: (250) 721-6200
Office: A417 Bob Wright Centre
Lab: B417 Bob Wright Centre
Lab phone: (250) 472-4813