Observing Changes in Ocean Carbonate Chemistry: Our Autonomous Future

Abstract

Purpose of Review We summarize recent progress on autonomous observations of ocean carbonate chemistry and the development of a network of sensors capable of observing carbonate processes at multiple temporal and spatial scales. Recent Findings The development of versatile pH sensors suitable for both deployment on autonomous vehicles and in compact, fixed ecosystem observatories has been a major development in the field. The initial large-scale deployment of profiling floats equipped with these new pH sensors in the Southern Ocean has demonstrated the feasibility of a global autonomous open-ocean carbonate observing system. Summary Our developing network of autonomous carbonate observations is currently targeted at surface ocean CO 2 fluxes and compact ecosystem observatories. New integration of developed sensors on gliders and surface vehicles will increase our coastal and regional observational capability. Most autonomous platforms observe a single carbonate parameter, which leaves us reliant on the use of empirical relationships to constrain the rest of the carbonate system. Sensors now in development promise the ability to observe multiple carbonate system parameters from a range of vehicles in the near future.

Evaluating the Sensor-Equipped Autonomous Surface Vehicle C-Worker 4 as a Tool for Identifying Coastal Ocean Acidification and Changes in Carbonate Chemistry

“…This gives the potential to use a combination of techniques to identify changes in coastal ocean acidification and understand the roles different habitats may be having in mitigating or enhancing ocean acidification. Coral reefs and seagrasses are often in shallow locations, making sampling hazardous and data collection harder, which can lead to data gaps, but they can have a No single platform will be optimal in all situations; there will always be trade-offs in mission lifetime, payload, power consumption, and measurement frequency [10]. Cameras and passive receivers require only a few watts [45], while instruments like pCO 2 sensors have higher power demands.…”

Technical Note: Stability of tris pH buffer in artificial seawater stored in bags

“…Technological advancements have led to more routine autonomous pH measurements over the past decade, providing opportunities to fill some gaps in time and space in discrete sampling programs (e.g, Byrne, 2014;Martz et al, 2015;Lai et al, 2018;Wang et al, 2019;Tilbrook et al, 2019). Globally, pH sensors now operate on hundreds of autonomous platforms including moorings and profiling floats, delivering unique datasets in the form of Eulerian and depth resolved Lagrangian time series (Johnson et al, 2017;Bushinsky et al, 2019;Sutton et al, 2019).…”

“…Independent validation is typically required for autonomous sensors to meet both weather and climate levels of uncertainty. For example, autonomous underway pCO2 systems (Pierrot et al, 2009), moorings (Bushinsky et al, 2019), and autonomous surface vehicles (Chavez et al, 2017;Sabine et al, 2020) are able to provide climate quality observations with an uncertainty of ± 2 μatm because traceable standard gases are frequently measured in situ. For pH measurements on profiling floats (Johnson et al, 2016), sensor performance is validated by comparing to a deep reference pH field that is calculated using empirical algorithms (Williams et al, 2016;Bittig et al, 2018;Carter et al, 2018).…”

Norwegian Sea net community production estimated from O<sub>2</sub> and prototype CO<sub>2</sub> optode measurements on a Seaglider

“…At thermodynamic equilibrium, knowledge of two of the four variables is sufficient to calculate the other two. Marine carbonate system variables are primarily measured on research ships, commercial ships of opportunity, moorings, buoys and floats (Hardman-Mountford et al, 2008;Monteiro et al, 2009;Takahashi et al, 2009;Olsen et al, 2016;Bushinsky et al, 2019). Moorings equipped with submersible sensors often provide limited vertical and horizontal, but good long-term temporal resolution (Hemsley, 2015).…”