“Particles” in the ocean are considered by scientists to be anything that is not dissolved. This could include dust, phytoplankton, fecal pellets, fish, and even logs or marine debris. Studying how these pieces of matter are spread out and grouped according to their size can provide insight to marine biodiversity, ecosystem health, and aspects of biogeochemical cycling, including the oceanic carbon cycle.
The Sea to Space Particle Investigation cruise will aim to improve the accuracy of particle size distribution products gathered from satellite and remote-sensing data records. These records contain critical information that can improve our understanding of how Earth’s living marine resources and carbon sequestration are responding to rising carbon dioxide levels as well as climate changes. The hope is that the application of instruments developed in conjunction with this expedition will allow an unprecedented view into the biological, geological, and chemical mechanics of the ocean – both in a local and global manner. The data collected and shared with the oceanographic community will lead to a transformative analysis understanding the roles of particle and plankton size in global biogeochemistry and other processes.
Satellite measurements of particle size distributions (PSD) are essential for researchers to create models of global processes. Color images and visuals made by orbiting satellites show comprehensive views of marine spaces and ecosystems that cannot be gathered by conventional ship or aircraft sampling, due to logistic issues such as distance from land and budgetary restraints. However, satellite algorithms for estimating particle size distributions are largely unverified due to a lack of confirmed datasets – there needs to be more direct measurements taken at the areas being interpreted by visual information from afar. These uncertainties generally exist because there are not enough surface observations and measurements done on-site for particle size distributions along with concurrent information from satellites.
Recording Ground Truth
The inability to use remote-sensing (such as imagery gathered by orbiting satellites) with validated certainty deters a cohesive and trustworthy foundation for studies. If this constriction were removed, extrapolating remote-sensing into algorithms and other predictive methods could open massive advances in knowledge of ecosystem dynamics and the ocean’s role in global biological, geological and chemical processes. With the results of this research cruise, Dr. Ivona Cetinić from NASA Goddard Space Flight Center/USRA along with co-investigators Dr. Wayne Homer Slade, Dr. P. Jeremy Werdell, and Dr. Margaret Estapa are hoping to usher in such advances.
The science team will create a process for unmanned optical measurement of marine particle size distributions and connect them to accompanying carbon export measurements. They will use a prototype instrument to continuously measure surface marine optical properties and particle size distribution. The distributions will then be validated with distinct bio/geochemical and carbon flux measurements and shared through a NASA public data archive. The goal is to make the new data available quickly for development and validation of ocean color satellite algorithms. This will dramatically improve accuracy in remote sensing estimates of marine particle size distributions and computations derived from these estimates.
Transiting from Honolulu to Seattle aboard Falkor, the team will use several instruments and tools to gather and measure optical and biogeochemical data from particles. Some will use light to measure qualities such as backscatter (refraction from light scattering due to particles), others will physically collect or filter water, with a CTD rosette or sediment trap. Remote-sensing data will also be gathered by NASA and the United States Geological Survey at the same time, observing the same areas where the team is working.
Written by: Logan Mock-Bunting
The material is based upon work supported by NASA under award No. NNH11HP16A.