Optical techniques for remote and in-situ characterization of particles pertinent to GEOTRACES

Abstract

a b s t r a c tField and laboratory characterization of marine particles is laborious and expensive. Proxies of particle properties have been developed that allow researchers to obtain high frequency distributions of such properties in space or time. We focus on optical techniques used to characterize marine particles in-situ, with a focus on GEOTRACES-relevant properties, such as bulk properties including particle mass, crosssectional area, particle size distribution, particle shape information, and also single particle optical properties, such as individual particle type and size. We also address the use of optical properties of particles to infer particulate organic or inorganic carbon. In addition to optical sensors we review advances in imaging technology and its use to study marine particles in situ. This review addresses commercially available technology and techniques that can be used as a proxy for particle properties and the associated uncertainties with particular focus to open ocean environments, the focus of GEOTRACES.

The Influence of Plankton Community Structure on Sinking Velocity and Remineralization Rate of Marine Aggregates

“…Vertical particle profiles determined with in situ camera systems are becoming an increasingly important tool to estimate carbon export fluxes (Boss et al, ; Guidi et al, ; Iversen et al, ). Camera‐based mass flux calculations utilize particle abundance data and a theoretical size versus SV relationship (Guidi et al, ).…”

Particulate concentration and seasonal dynamics in the mesopelagic ocean based on the backscattering coefficient measured with Biogeochemical‐Argo floats

“…The annual cycle is absent at other regions (e.g., Mediterranean basins, North Atlantic subtropical gyre, and Indian Ocean). Assuming a specific attenuation coefficient at 660 nm of 0.8 m 2 /mg and a specific backscattering coefficient at 660 nm of 0.008 m 2 mg −1 , Boss et al [2015] predicted that the range of beam attenuation measured in such waters will be 0.005-0.015 m −1 while that for backscattering will be 5-15 ×10 −5 m −1 . Despite the significant differences in b bp (700) between sensors, we find the measured values to be consistent with past measurements of suspended particulate at depth; Brewer et al [1976] report values varying from 5 to 20 μg/kg between 900 and 1000 m [Brewer et al, 1976, Figure 1] in the North Atlantic.…”

“…Back in the 1970s, the Geochemical Ocean Sections Study program performed basin-scale sampling to map the distribution of particulate material throughout ocean basins [Brewer et al, 1976]. Since these processes regulate one of the main processes contributing to the sequestration of atmospheric carbon dioxide into the deep ocean, it is of great interest to be able to monitor the concentration and dynamics of particles at depth.…”

The Argo Program: Present and Future

“…, ion sensitive field effect pH sensors (K.S. , and fluorometers for chlorophyll a fluorescence and backscattering for particulate matter (Boss et al, 2015).…”