Shipboard measurements of atmospheric oxygen using a vacuum-ultraviolet absorption technique

Abstract

We have developed an instrument for making continuous, field‐based, part‐per‐million (ppm) level measurements of atmospheric oxygen concentration, and have implemented it on research cruises in the equatorial Pacific and Southern Oceans. The instrument detects changes in oxygen by the absorption of vacuum ultraviolet (VUV) radiation as it passes through a flowing gas stream, and has a precision comparable to existing laboratory techniques. Here we describe the VUV instrument and present atmospheric O2 and CO2 data collected from the NOAA ship Ka'imimoana in the equatorial Pacific during April and May of 1998, and from the NSF ship Lawrence M. Gould in the Southern Ocean during October 1998. These data represent the first field‐based measurements of atmospheric O2, and significant additions to the O2 datasets in these regions. Our boreal‐springtime equatorial measurements reveal significant short‐term variations in atmospheric O2, resulting from variations in atmospheric mixing relative to the strong interhemispheric gradient. Our austral‐springtime Southern Ocean observations confirm the low O2 concentrations seen in flask samples from this region, allow the separate identification of oceanic and industrial influences on CO2, and provide evidence of a Southern Ocean source for CO2 at this time of year. These shipboard VUV observations do not provide any evidence to support coupled ocean–atmosphere model predictions of a large decreasing atmospheric O2 gradient between equatorial and high‐southern latitudes.

Role of sea ice in global biogeochemical cycles: emerging views and challenges

“…Seen as an impervious cap, sea ice would drastically reduce air-sea CO 2 exchange [Stephens and Keeling, 2000]. However this is hardly the case in practice, because of the presence of open water within the pack (leads and polynyas), providing pathways for atmosphere-ocean gas exchanges [Morales Maqueda and Rahmstorf, 2002].…”

CO<sub>2</sub>, δO<sub>2</sub>/N<sub>2</sub> and APO: observations from the Lutjewad, Mace Head and F3 platform flask sampling network

“…(Kozlova et al, 2008;Stephens et al, 2003) shows the relationship between changes in the O 2 concentration and changes in δO 2 /N 2 .…”

“…Since then other methods have been developed to enable atmospheric O 2 measurements at the required precision of 1:10 6 (WMO, 2009). Current techniques include mass-spectrometry (Bender et al, 1994), paramagnetic analyzers (Manning et al, 1999), vacuum ultraviolet absorption (Stephens, 1999;Stephens et al, 2003), gas chromatography (Tohjima, 2000) and fuel cells (Patecki and Manning, 2007;Stephens et al, 2007;Thompson et al, 2007). Each of these techniques has its specific I. T. van der Laan-Luijkx et al: CO 2 , δO 2 /N 2 and APO observations from Lutjewad, Mace Head and F3 advantages and disadvantages, not only related to the O 2 sensor obtaining the required precision, but also to the possibility to run the instrument automatically, remotely or in harsh conditions, e.g.…”

Detection of regional scale sea-to-air oxygen emission related to spring bloom near Japan by using in-situ measurements of the atmospheric oxygen/nitrogen ratio

“…techniques have been developed to make in-situ measurements of the atmospheric O 2 /N 2 ratio, such as the paramagnetic oxygen analyzer system (Lueker et al, 2003;Manning et al, 1999), the vacuum ultraviolet absorption method (Stephens, 1999;Stephens et al, 2003), and the fuel cell analyzer systems (Stephens et al, 2007 and references therein). Previous studies have revealed that a sampling line for insitu O 2 /N 2 measurements requires careful design to prevent fractionation of O 2 from N 2 .…”