Net Community Production in a Productive Coastal Ocean From an Autonomous Buoyancy‐Driven Glider

Net community production (NCP), an analog of carbon export out of the surface ocean, is often estimated using budgets of dissolved oxygen. Accurate estimates of oxygen‐based NCP, especially in dynamic coastal regions, require constraints on vertical transport of water with O2 out of equilibrium with...

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Bibliographic Details
Published in:Journal of geophysical research. Oceans 2019-06, Vol.124 (6), p.4188-4207
Main Authors: Haskell, W. Z., Hammond, D. E., Prokopenko, M. G., Teel, E. N., Seegers, B. N., Ragan, M. A., Rollins, N., Jones, B. H.
Format: Article
Language:English
Subjects:
Analogs
Atmosphere
Autonomous underwater vehicles
autonomous vehicles
Beryllium
Beryllium 7
Bubbles
Budgeting
Budgets
Buoyancy
Carbon
Carbon dioxide
Carbon dioxide atmospheric concentrations
carbon export
Coastal dynamics
coastal oceanography
Coastal zone
Communities
Constraints
Cooling rate
Dissolved oxygen
Estimates
Exports
Geophysics
Gliders
Heating
Injection
Measurement techniques
Mixed layer
net community production
Oceans
Organic chemistry
Oxygen
Patchiness
Productivity
Regions
Resolution
Sampling
Supersaturation
Surface mixed layer
Transport
Underwater vehicles
Vertical advection
Wind speed
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Summary:Net community production (NCP), an analog of carbon export out of the surface ocean, is often estimated using budgets of dissolved oxygen. Accurate estimates of oxygen‐based NCP, especially in dynamic coastal regions, require constraints on vertical transport of water with O2 out of equilibrium with the atmosphere, nonsteady state change in the oxygen inventory, heating/cooling‐driven O2 disequilibrium, and the rate of bubble injection from wave activity. The latter two are typically evaluated by using discrete measurements of the O2/Ar ratio in lieu of O2 only. Because sophisticated sampling and measurement techniques are required to make these measurements, they are often limited in spatiotemporal resolution. However, high‐resolution estimates of NCP may be useful in determining small‐scale patchiness in export. In this study, we calculated high‐resolution NCP in coastal Southern California using dissolved oxygen measurements made by an autonomous buoyancy‐driven Slocum glider and an empirical relationship derived using discrete measurements of O2/Ar in the surface mixed layer to remove the influence of bubble injection, which accounted for approximately one fourth of the O2 supersaturation observed. Using estimates of vertical transport from wind speed‐based parameterizations, previously validated using a 7Be budget, we were able to correct for the physical biases to the signal, which are known to significantly influence dissolved oxygen budgets in this region. Our results agree well with previously published NCP estimates for the study area but also reveal higher‐frequency variability that discrete sampling was unable to resolve, suggesting that this approach may be useful in other regions with well‐constrained vertical transport rates. Plain Language Summary The ocean takes up carbon dioxide from the atmosphere through a process referred to as “the biological pump.” “Carbon export” refers to the amount of carbon removed by this process and is therefore an important quantity in determining the ocean's role as a sink for atmospheric carbon dioxide and significantly influences ocean chemistry. Carbon export is often estimated using budgets of oxygen in the surface ocean because oxygen is affected by the same processes. However, bubbles introduced through wave activity can bias oxygen budgets if not accounted for using precise measurements, which are often made in low spatiotemporal resolution and thus can miss patchy, high‐productivity events believed to
ISSN:2169-9275
2169-9291
DOI:10.1029/2019JC015048