Ocean-air N[subscript 2]O trace gas fluxes in Halifax Harbour derived from open-path FTIR measurements

• Main Author: Hellmich, Martin
• Other Authors: Wiacek, Aldona, 1977-
• Format: Text
• Language: English
• Published: Halifax, N.S. : Saint Mary's University 2022
• Subjects: Fourier transform infrared spectroscopy > Measurement > Halifax Harbour (N.S.); Ocean-atmosphere interaction > Halifax Harbour (N.S.); Atmospheric nitrous oxide > Halifax Harbour (N.S.); Micrometeorology > Halifax Harbour (N.S.); Northwest Atlantic
• Online Access: http://library2.smu.ca/xmlui/handle/01/31051

1 online resource (133 pages) : colour illustrations, colour maps, charts (chiefly colour), graphs Includes abstract and appendix. Includes bibliographical references (pages 112-116). Open-Path Fourier Transform Infrared (OP-FTIR) spectroscopy is an established technique for path-average measurements of atmospheric trace gas concentrations. We describe the novel application of OP-FTIR to measure ocean-air gas fluxes across 586 m of Halifax Harbour (northwest Atlantic coast), also using a 3-D sonic anemometer and two vertically separated retroreflector arrays. We present spectroscopic retrievals of nitrous oxide (N 2 O) concentration, micrometeorological data characteristics, and flux-gradient method calculations of ocean-air N 2 O flux. From Dec. 2020 to Apr. 2021 the calculated ocean sink of −10.81 kg N2O ha −1 agreed broadly with a global model of thermal (solubility-driven) N 2 O flux. A powerful short-term ocean source event observed on Dec. 15-17 (+2.00 kg N2O ha −1 ) correlated with high winds and strong ocean cooling that plausibly caused surface overturning and the upwelling of N 2 O-rich deeper waters. The method presented is well suited to high frequency monitoring of coastal N 2 O fluxes, necessary to resolve complex physical, chemical and biological processes.