Glider-based observations of CO<sub>2</sub> in the Labrador Sea

Abstract

Abstract. 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 CO2 measurements. We need to develop robust methods to evaluate novel CO2 sensors for gliders. Here we present results from testing the performance of a novel CO2 optode sensor (Atamanchuk et al., 2014), deployed on a Slocum glider, in the Labrador Sea and on the Newfoundland Shelf. This paper (1) investigates the performance of the CO2 optode on two glider deployments, (2) demonstrates the utility of using the autonomous SeaCycler profiler mooring (Send et al., 2013; Atamanchuk et al., 2020) 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 O2 and pCO2 in the Labrador Sea. The Aanderaa CO2 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 (τ95>100 s), affected by different behavior when profiling through small (<3 ∘C) vs. large (>10 ∘C) changes in temperature over similar time intervals. We compare the glider and SeaCycler O2 and CO2 observations and estimate the glider data uncertainty as ± 6.14 and ± 44.01 µatm, respectively. From the Labrador Sea mission, we point to short timescales (<7 d) and distance (<15 km) scales as important drivers of change in this region.

The distribution of subarctic and boreal deep‐sea demersal fish assemblages across environmental gradients of the northwest Atlantic

“…This process provides an important influx of atmospheric gases such as oxygen and carbon dioxide to deeper depths, ventilating the deeper layers of the water column (Lazier et al, 2002). Thus, the Labrador Sea is both a vital region for the sequestering of anthropogenic carbon and an intense carbon sink (von Oppeln‐Bronikowski et al, 2021).…”

Best practices for operating underwater gliders in Atlantic Canada

“…Other glider work during this period focused on measuring the eddy exchange and Ekman across-shelf transport in the Labrador Sea and Newfoundland region (Howatt et al, 2018) using glider deployed as part of the multi-year international Ventilations, Interactions and Transport Across the Labrador Sea (VITALS) project (2013)(2014)(2015)(2016)(2017)(2018). VITALS also saw deployments in the winter utilizing new techniques in applying thrusters and pCO 2 sensors (von Oppeln-Bronikowski et al, 2021a).…”

“…Memorial has also improved the capability of gliders to sample dissolved gasses such as O 2 and CO 2 (Bishop, 2008;von Oppeln-Bronikowski et al, 2021a) on the shelf and in the Labrador Sea. The Labrador Sea work posed challenges around sensor development, making reliable glider-based CO 2 measurements and pushing the glider's endurance window.…”

“…Reliable measurements are not yet made in Atlantic Canada, but glider groups are working on implementing new sensors. Memorial and CEOTR have been conducting experimental testing with prototype pCO 2 (Atamanchuk et al, 2014;von Oppeln-Bronikowski et al, 2021a) and ISFET pH sensors (Branham et al, 2016;Johnson et al, 2016) on gliders. CEOTR is the only group to have implemented the SUNA UV (Carrol et al, 2007) Nitrate sensor (Comeau et al, 2007).…”