Glider-based observations of CO₂ in the Labrador Sea

• Main Authors: N. von Oppeln-Bronikowski, B. de Young, D. Atamanchuk, D. Wallace
• Format: Article
• Language: English
• Published: Copernicus Publications 2021-01-01
• Series: Ocean Science
• Online Access: https://os.copernicus.org/articles/17/1/2021/os-17-1-2021.pdf
• ISSN: 1812-0784; 1812-0792

<p>Ocean gliders can provide high-spatial- and temporal-resolution data and target specific ocean regions at a low cost compared to ship-based measurements. An important gap, however, given the need for carbon measurements, is the lack of capable sensors for glider-based <span class="inline-formula">CO₂</span> measurements. We need to develop robust methods to evaluate novel <span class="inline-formula">CO₂</span> sensors for gliders. Here we present results from testing the performance of a novel <span class="inline-formula">CO₂</span> optode sensor <span class="cit" id="xref_paren.1">(<a href="#bib1.bibx1">Atamanchuk et al.</a>, <a href="#bib1.bibx1">2014</a>)</span>, deployed on a Slocum glider, in the Labrador Sea and on the Newfoundland Shelf. This paper (1) investigates the performance of the <span class="inline-formula">CO₂</span> optode on two glider deployments, (2) demonstrates the utility of using the autonomous SeaCycler profiler mooring <span class="cit" id="xref_paren.2">(<a href="#bib1.bibx47">Send et al.</a>, <a href="#bib1.bibx47">2013</a>; <a href="#bib1.bibx3">Atamanchuk et al.</a>, <a href="#bib1.bibx3">2020</a>)</span> to improve in situ sensor data, and (3) presents data from moored and mobile platforms to resolve fine scales of temporal and spatial variability of <span class="inline-formula">O₂</span> and <span class="inline-formula"><i>p</i></span>CO<span class="inline-formula">₂</span> in the Labrador Sea. The Aanderaa <span class="inline-formula">CO₂</span> optode is an early prototype sensor that has not undergone rigorous testing on a glider but is compact and uses little power. Our analysis shows that the sensor suffers from instability and slow response times (<span class="inline-formula"><i>τ</i>₉₅&gt;100</span> s), affected by different behavior when profiling through small (<span class="inline-formula">&lt;3</span> <span class="inline-formula">^∘</span>C) vs. large (<span class="inline-formula">&gt;10</span> <span class="inline-formula">^∘</span>C) changes in temperature over similar time intervals. We compare the glider and SeaCycler <span class="inline-formula">O₂</span> and <span class="inline-formula">CO₂</span> observations and estimate the glider data uncertainty as <span class="inline-formula">±</span> 6.14 and <span class="inline-formula">±</span> 44.01 <span class="inline-formula">µ</span>atm, respectively. From the Labrador Sea mission, we point to short timescales (<span class="inline-formula">&lt;7</span> d) and distance (<span class="inline-formula">&lt;15</span> km) scales as important drivers of change in this region.</p>