Constraining the Biological Pump on Seasonal Scales through Autonomous Oxygen Observations from Profiling Floats
Constraining the Biological Pump on Seasonal Scales through Autonomous Oxygen Observations from Profiling Floats
Abstract:
Understanding the biological pump is limited by our knowledge of the governing processes and drivers as well as by the scarcity of data related to its function. Autonomous float observations can help mitigate both by providing a cost-efficient way to obtain in-situ observations at improved temporal and spatial scales compared to traditional sampling methods. Oxygen observations are especially suited for this purpose because of the tight coupling between the oxygen (O2) and carbon (C) cycle and the availability of a reliable and accurate O2 sensor technology.
On seasonal scales, oxygen remineralization below the euphotic zone causes an accumulation of an O2 deficit which provides a quantitative estimate of the mesopelagic C flux and its attenuation. This approach is insensitive to single export events of fast-sinking, large particles. Instead, it integrates over short-term variability in the break-up/remineralization of small particles because of its cumulative nature. As such, it provides a valuable comparison with event-focused flux estimates from, e.g., particle-based measurements.
Complementing the mesopelagic, net community production (NCP) in the surface and sub-surface provides a bound to export production. NCP can be derived from a timeseries of observed O2 profiles in conjunction with a simple 1D mixing and gas exchange model.
The examples of mesopelagic C flux and surface NCP presented here are based on Bio-Argo floats deployed in the subpolar North Atlantic as well as in the North and South Atlantic subtropical gyres. In addition, they are used to illustrate the limits that ocean physics (e.g., deep vs. shallow winter mixing) sets to the applicability of above analyses.
On seasonal scales, oxygen remineralization below the euphotic zone causes an accumulation of an O2 deficit which provides a quantitative estimate of the mesopelagic C flux and its attenuation. This approach is insensitive to single export events of fast-sinking, large particles. Instead, it integrates over short-term variability in the break-up/remineralization of small particles because of its cumulative nature. As such, it provides a valuable comparison with event-focused flux estimates from, e.g., particle-based measurements.
Complementing the mesopelagic, net community production (NCP) in the surface and sub-surface provides a bound to export production. NCP can be derived from a timeseries of observed O2 profiles in conjunction with a simple 1D mixing and gas exchange model.
The examples of mesopelagic C flux and surface NCP presented here are based on Bio-Argo floats deployed in the subpolar North Atlantic as well as in the North and South Atlantic subtropical gyres. In addition, they are used to illustrate the limits that ocean physics (e.g., deep vs. shallow winter mixing) sets to the applicability of above analyses.