Project Funding: 2011 - 2014

NRA: 2010 NASA: Carbon Cycle Science   

Funded by NASA

Abstract:
Carbon export, the vertical transport of organic carbon from the surface ocean into its interior via sinking particles, is a critical part of the upper ocean carbon budget. However, our ability to remotely assess carbon export rates globally remains primitive at best as carbon export is most commonly estimated as the product of remotely sensed values of net primary production (NPP) multiplied by a very simple export-ratio model. These models may provide a reasonable assessment of present state of mean carbon export, but they will not assess changes in export as these are purely empirical models and none of the critical information about mechanisms driving export are included. To make that next step towards a mechanistic assessment of ocean carbon flux we need knowledge of upper ocean particle source material concentrations and characteristics and knowledge of how physical oceanographic processes alter upper ocean particle fields and package suspended materials into sinking particles that are exported into the ocean interior. Here we propose a coupled field, imagery analysis and modeling program aimed at understanding the mechanisms driving carbon export and developing novel tools for its remote assessment. Specifically, we will conduct two ~3200 km long meridional transects across the North Atlantic (~40 to 20ºN) collaborating with the Bermuda Atlantic Time Series (BATS). We will sample carbon export (via 234Th disequilibria) from vertical water samples and surface samples from underway collection (with 10 km spatial resolution). Concentrations of the radioisotope thorium-234 are an excellent index for euphotic zone particle removal as measured by its disequilibrium with its parent (238U) and recent technical advances enable its high spatial resolution sampling from a ship’s underway flow system. Upper ocean particle concentrations and characteristics will be sampled by measuring inherent optical properties, phytoplankton abundances and pigments, size-fractionated inherent optical property and chlorophyll concentrations, particulate organic carbon, transparent exopolymer particle (TEP) concentrations, and the particle size distribution (PSD) spectrum. These observations will be made both underway from the ship’s surface underway system and as vertical profiles. This work will constrain the types and concentrations of particles and processes that are leading to particle export. Satellite ocean color observations of inherent optical properties and the PSD will be integrated into the interpretation of the field observations. A key element of our proposal is the simultaneous observations of particle export and source material characteristics and the physical drivers of particle aggregation. Recent modeling studies have shown that Lagrangian Coherent Structures (LCSs) can be determined from merged satellite altimetry observations. LCSs define the attracting and repelling surfaces in 2-D flow fields and provide an excellent, diagnostic tool for assessing regions where submesoscale particle aggregation will occur as well as vertical motions at fronts. The relationships among LCS locations and intensities will be evaluated using observations from the ship transects and from advance ocean color data products. The proposed combination of high-resolution field observations, remote sensing data analysis and assessment of LCSs is a unique feature of our work. This proposal responds to Section 3.5 (Synthesis and integrative research) in the Carbon Cycle call for proposals.

2011 NASA Carbon Cycle & Ecosystems Joint Science Workshop Poster(s)

• Regional to Global Scale Phytoplankton Dynamics: The SeaWiFS Legacy   --   (Dave Siegel, Michael Behrenfeld, Charles McClain, Many Others)   [abstract]

More details may be found in the following project profile(s):

• NASA Ocean Biology & Biogeochemistry (OBB) Project Profile