The Experiment

Four principal investigators, their graduate students and collaborators will conduct an NSF-funded autonomous oceanographic experiment from April–July 2008. Using floats and seagliders, we will study an important component of the oceanic carbon system – the North Atlantic Spring Bloom (NAB). This will be supplemented by a process cruise in May 2008 with collaboration by another dozen PI’s.

The Principal Investigators

The Problem

About 25% of the global ocean uptake of CO₂ occurs in the North Atlantic, primarily during phytoplankton blooms. The bloom’s complex spatial and temporal structure (resulting from interacting circulation, mixing and bloom dynamics) challenges traditional means of ocean observation (i.e. ship-based sampling and remote sensing).

The Field Program

Recent advances in sensors and autonomous platforms make it possible to observe physical, chemical and biological properties with high spatial and temporal resolution and without the presence of a ship. We will deploy sensor-equipped floats and seagliders south of Iceland during the 2008 spring bloom. Three cruises are planned (Deployment, Process, Recovery), with CTD sampling and measurements near the autonomous instruments in each case. A complete suite of carbon-cycle related measurements will be made on the Process cruise aboard the R/V Knorr, roughly 1-22 May 2008.

The Instruments

The Biofloats are designed to accurately follow the three-dimensional motion of water parcels within the mixed layer of the ocean, through a combination of neutral buoyancy and high drag provided by a 1 m-diameter black drogue. The buoyancy of the float is carefully controlled by design and active measurements so that useful estimates of mixed layer turbulent energies and fluxes can be made. The two Biofloats (47, 48) can also profile vertically; in this experiment the maximum profiling depth is 260 m. Additional details.

The Seagliders are buoyancy driven autonomous underwater vehicles that glide from the ocean surface to as deep as 1000 m and back. Gliders steer through the water by controlling attitude (pitch and roll) and can navigate between waypoints to execute survey patterns or hold station. From the Seagliders' motion, estimates of oceanic horizontal currents can also be made. Four Seagliders (140, 141, 142, 143) are deployed in the NAB08 experiment. Additional details.

Over 60 channels of data are regularly sampled by the Biofloats and Seagliders, providing a unique time-space-resolved picture of the physical, biological and chemical properties of the bloom. Both platforms contain sensors for measuring salinity, temperature, pressure, chlorophyll fluorescence, backscattering (700 nm) and oxygen concentration. The Biofloats contain additional sensors for measuring beam attenuation, photosynthetically available radiation (PAR) and the hyperspectral light field (E_d, L_u @ 320 - 950 nm). Each Biofloat carries a UV spectrophotometer from which in situ nitrate estimates can be made. Three gliders (141, 142, 143) contain additional backscattering channels (470 nm, 532 nm) as well as additional chlorophyll and CDOM fluorometers. Both platforms use the Iridium satellite system to send data and receive commands.

The Funding

The National Science Foundation (NSF) is an independent US government agency responsible for promoting science and engineering through research programs and education projects. This experiment is funded via the Carbon and Water in Earth Systems program, aimed at closing significant gaps in our understanding of the complex relationships between and within the global water and carbon cycles.

What is a Collaboratory?

As an amalgamation of Collaboration and Laboratory, this collaboratory itself represents an experiment in the use of information technology to facilitate the operation, data fusion, analysis, and human interaction of a real-life, multi-investigator oceanographic experiment. The software supporting this collboratory is based on the Drupal Content Management System.

Who Can Join?

Anyone is welcome to browse this web site collaboratory. To make comments on the site, you must create a login and be authenticated by an administrator. If you are a scientist working in a related field and would like to know more, please contact one of the main PIs -- keeping in mind that you are likely to get a quicker response from a PI who is not at sea.