Understanding Biogeochemical and Physical Controls on Methane Air-Sea Exchange Fluxes in the Pacific Ocean

<p>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.</p>

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

Masters Thesis

Year dc:date.available

2022

Author dc:creator

• Raney, Sarah

Contributors dc:contributor

• Dr. Alan Shiller
• Dr. Christopher Hayes
• Dr. Kevin Dillon

• methane
• biogeochemistry
• oceanography
• Pacific
• air-sea exchange
• trace elements
• Environmental Chemistry

Repository record dc:identifier

https://aquila.usm.edu/masters_theses/890

OAI identifier oai:identifier

oai:aquila.usm.edu:masters_theses-1953