Date of Award

Spring 5-2022

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)

School

Ocean Science and Engineering

Committee Chair

Dr. Alan Shiller

Committee Chair School

Ocean Science and Engineering

Committee Member 2

Dr. Christopher Hayes

Committee Member 2 School

Ocean Science and Engineering

Committee Member 3

Dr. Kevin Dillon

Committee Member 3 School

Ocean Science and Engineering

Abstract

Methane and trace element samples were collected on GEOTRACES GP15 Pacific Meridional Transect (PMT) cruise conducted between the Aleutian Islands (57 °N) and Tahiti (20 °S) from September to November 2018. Uncertainty in methane air-sea exchange fluxes was determined using a propagation of errors approach. Fluxes ranged from -0.88 to 4.9 µmol CH4 m-2 d-1. Average CH4 flux along the Alaskan margin was 2.2 ± 2.9 µmol CH4 m-2 d-1. Methane fluxes decreased moving southward and increased to their open ocean maximum around 20 °N before declining in equatorial waters. Near 20 °N, phosphorus-limiting conditions were observed, suggesting methylphosphonate (MPn) utilization may have occurred to elevate CH4 fluxes. Methane fluxes measured at open ocean stations ranged from -0.31 to 2.9 µmol CH4 m-2 d-1, matching those reported in previous studies. Atmospheric methane and near-surface dissolved methane concentrations differed significantly between the hemispheres (paired Student’s t test, p < 0.01). The temperate North Pacific average CH4 fluxes (0.40 ± 0.76 µmol CH4 m-2 d-1) significantly differed from average fluxes measured in the subtropical North Pacific (1.5 ± 0.80 µmol CH4 m-2 d-1; p < 0.01) and the equatorial Pacific (0.92 ± 0.44 µmol CH4 m-2 d-1; p < 0.05). Lanthanum (La) to ytterbium (Yb) ratios and light rare earth element (LREEs) to heavy (HREEs) ratios were lower in South Pacific compared to North Pacific, indicating possible methane oxidation through use of LREEs as enzyme co-factors.

ORCID ID

0000-0003-4437-7144

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