Jonathan D. Ware

Carbon dioxide flux techniques performed during GasEx-98

A comprehensive study of air–sea interactions focused on improving the quantification of CO2 fluxes and gas transfer velocities was performed within a large open ocean CO2 sink region in the North Atlantic. This study, GasEx-98, included shipboard measurements of direct covariance CO2 fluxes, atmospheric CO2 profiles, atmospheric DMS profiles, water column mass balances of CO2, and measurements of deliberate SF6–3He tracers, along with air–sea momentum, heat, and water vapor fluxes. The large air–sea differences in partial pressure of CO2 caused by a springtime algal bloom provided high signals for accurate CO2 flux measurements. Measurements were performed over a wind speed range of 1–16 m s−1 during the three-week process study. This first comparison between the novel air-side and more conventional water column measurements of air–sea gas transfer show a general agreement between independent air–sea gas flux techniques. These new advances in open ocean air–sea gas flux measurements demonstrate the progress in the ability to quantify air–sea CO2 fluxes on short time scales. This capability will help improve the understanding of processes controlling the air–sea fluxes, which in turn will improve our ability to make regional and global CO2 flux estimates.

Diffuse high-bandwidth optical communications

High speed underwater optical communications has at least three distinct advantages over acoustic communications. The data rates achievable are high (1 to 10 Mbps), the latency from when data is sent to when data is received is low, and there is no acoustic noise associated with transmission. Of course one of the biggest limitations of an optical approach underwater is the rapid attenuation of optical signals due to spreading loss, scattering, and absorption. Nonetheless, communication signals have been broadcast, received, and decoded over distances of 100 to 200 meters. High data rates and low latency make optical communications an attractive human interface to underwater systems, such as wireless control of underwater vehicles. Underwater optical communications is generally well-suited to multiple platform environments, where acoustic silence and limited range avoids interference between platforms. High data rates are advantageous in data retrieval applications, where, for one example, wireless data retrieval would make deployment and recovery of certain systems more economical. Recent engineering developments and accompanying experimental data are put forth in this paper, and the implications for future development are discussed.

A network-based telemetry architecture developed for the Martha's Vineyard Coastal Observatory

Underwater observatories with real-time data and virtually unlimited power transmission capabilities compared to traditional oceanographic moorings are beginning to provide scientists with continuous access to the coastal and open ocean. However, for any coastal observatory to serve as a cost-effective system for the collection of long-term scientific and environmental data, it must have a simple, upgradeable power and telemetry system and an instrument interface that is compatible with existing standards. It must be designed for extended environmental exposure and ease of service to avoid high maintenance costs. Most importantly, the observatory must be accessible to all potential users, including students, scientists, engineers, and policy makers. This strategy was applied to the design of the Marthas Vineyard Coastal Observatory on the south shore of the island of Marthas Vineyard. The new facility, and in particular its system architecture, as developed by the Woods Hole Oceanographic Institution with support from the National Science Foundation, are described.

An acoustically-linked deep-ocean observatory

A buoy-based observatory that uses acoustic communication to retrieve data from water column and seafloor instruments has been developed and deployed in 2362 m of water offshore Vancouver Island. The system uses high-rate (5000 bps) acoustic modems that are power-efficient (on order 1000 bits per joule) to telemeter data from an ocean bottom seismometer and a sensor monitoring a cold seep site near the Nootka fault. The buoy includes a Linux-based embedded controller, the modem base station and meteorological sensors. Data is off-loaded from the buoy using ftp, and remote login capability allows the acoustic communication schedule to be modified when instruments are added or removed from the network. The system has been operational for one year, typically transferring more than 500 Kbytes of data per day from two seafloor instruments.

A Surface Mooring for Air–Sea Interaction Research in the Gulf Stream. Part I: Mooring Design and Instrumentation

The design of a surface mooring for deployment in the Gulf Stream in the Mid-Atlantic Bight is described. The authors’ goals were to observe the surface meteorology; upper-ocean variability; and air‐sea exchanges of heat, freshwater, and momentum in and near the Gulf Stream during two successive 1-yr deployments. Of particular interest was quantifying these air‐sea fluxes during wintertime events that carry cold, dry air from the land over the Gulf Stream. Historical current data and information about the surface waves were used to guidethedesignofthe surfacemooring. Thesurfacebuoy provided theplatformforboth bulkmeteorological sensors and a direct covariance flux system. Redundancy in the meteorological sensors proved to be a largely successful strategy to obtain complete time series. Oceanographic instrumentation was limited in size by considerations of drag; and two current meters, three temperature‐salinity recorders, and 15 temperature recorders were deployed. Deployment from a single-screw vessel in the Gulf Stream required a controlleddriftsternfirstovertheanchorsites.Thefirstdeploymentlastedtheplannedfullyear.Theseconddeployment ended after 3 months when the mooring was cut by unknown means at a depth of about 3000 m. The mooring was at times in the core of the Gulf Stream, and a peak surface current of over 2.7 m s 21 was observed. The 15-monthrecordsofsurfacemeteorologyandair‐seafluxescapturedtheseasonalvariabilityaswellasseveral cold-air outbreaks; the peak observed heat loss was in excess of 1400 W m 22 .

A Surface Mooring for Air–Sea Interaction Research in the Gulf Stream. Part II: Analysis of the Observations and Their Accuracies

AbstractA surface mooring was deployed in the Gulf Stream for 15 months to investigate the role of air–sea interaction in mode water formation and other processes. The accuracies of the near-surface meteorological and oceanographic measurements are investigated. In addition, the impacts of these measurement errors on the estimation and study of the air–sea fluxes in the Gulf Stream are discussed. Pre- and postdeployment calibrations together with in situ comparison between shipboard and moored sensors supported the identification of biases due to sensor drifts, sensor electronics, and calibration errors. A postdeployment field study was used to further investigate the performance of the wind sensors. The use of redundant sensor sets not only supported the filling of data gaps but also allowed an examination of the contribution of random errors. Air–sea fluxes were also analyzed and computed from both Coupled Ocean–Atmosphere Response Experiment (COARE) bulk parameterization and using direct covariance mea...

The Martha's Vineyard Coastal Observatory: a long term facility for monitoring air-sea processes

The desire to gain a better understanding of coastal processes over the past decade has led to an increased focus on coastal research in the scientific community. As an estimated 50% of humanity lives within 100 miles of a coastline and as national defense initiatives shift towards littoral regions, this interest in coastal processes will continue to grow. The south shore of the island of Marthas Vineyard is an ideal location for the study of the near-shore environment, due to its uninterrupted, south-facing beach with open ocean exposure. This area is frequented by all types of weather systems, including winter storms, hurricanes, and calm summer conditions. The seasonal variations provide a wide range of biological activity as well. To support long-term research in these areas, the Woods Hole Oceanographic Institution (WHOI), supported by the National Science Foundation, is currently developing and installing a coastal observatory system on the south shore of the Vineyard in Edgartown, Massachusetts.

Air-Water Flux Reconciliation Between the Atmospheric CO2 Profile and Mass Balance Techniques

Studies deploying atmospheric flux-profile techniques in laboratory wind-wave tanks have been performed to demonstrate and verify the use of airside turbulent transport models and micrometeorological approaches to accurately determine air-water gas transfer velocities. Air-water gas transfer velocities have been estimated using the CO2 atmospheric flux-profile technique in laboratory wind-wave tanks both at the NASA Wallops Flight Facility, USA and Kyoto University, Japan. Gas fluxes using the flux-profile and the waterside mass balance techniques have been reconciled. Air-water fluxes of H2O and momentum were also measured simultaneously in a linear wind-wave tank. The waterside mass balances used the evasion of SF6. The CO2, H2O, and momentum fluxes were calculated using the atmospheric flux-profile technique over a wind speed range of 1 to 14 m s−1. The CO2 and H2O atmospheric profile model uses airside turbulent diffusivities derived from momentum fluxes. These studies demonstrate that the quantification of air-water CO2 fluxes using the atmospheric flux-profile technique can be implemented in the laboratory. The profile technique can be used to measure an air-water flux in much less time than a mass balance. Effects of surfactants, wind speed, and wind stress on air-water transfer are also explored using the flux-profile technique. Validation of the air-water CO2 gas exchange in laboratory wind-wave tanks provides evidence and support that this technique may be used in field studies.

Wireless data harvesting using the AUV Sentry and WHOI optical modem

The optical communications group at Woods Hole Oceanographic Institution has demonstrated wireless optical transmission of data from a seafloor node to the Sentry AUV. This effort is based on the latest version of the optical modem under continual development at WHOI, and it builds on fieldwork conducted in 2012 and 2013 during which we successfully transferred data from seafloor-deployed optical modem systems using a wire-lowered optical modem from a ship. While our previous work used a high-bandwidth optical modem for the data uplink and an acoustic modem “backlink” to control the file transfer, the optical modem described in this paper supports fully bidirectional optical communication-essentially subsea WiFi. A subordinate objective of our work was to literally map the operational space for an AUV-bottom node optical link. Armed with this spatial map, we can plan for future “connected” AUV operations in support of data mule, inspection, manipulation, and other underwater semi-autonomous tasks.

A leveling system for an ocean-bottom seismometer

As part of a new broad-band, ocean-bottom seismometer (OBS) system that has been developed at the Woods Hole Oceanographic Institution, a gimbaled leveling system was designed and built. The goal of the broad-band system is to measure ocean-bottom vibrations from a period of 120 seconds up to 20 Hertz. During system deployment, a sphere containing the seismic sensor is dropped into sediment on the ocean bottom. Seismic sensors need to be leveled before use, and it is not practical to accurately control the attitude of the sphere as it settles on the ocean bottom. The sphere holds the seismic sensor in gimbals whose axes have brakes. The gimbal axes have brakes to prevent tilting in response to slow horizontal accelerations that would complicate long-period seismometer response. To level the seismic sensor, the brakes are released, the righting moment of the seismic sensor in the gimbals levels the seismometer attitude, and the brakes are reasserted. The brake systems were designed to have zero play and had to be modified to raise the lowest system natural frequency above 20 Hertz. This paper describes the mechanical aspects of the system and the modifications needed to push up the mechanical resonances. Twenty-five of the OBS systems have been built and deployed off Hawaii as part of the Plume-Lithosphere Undersea Melt Experiment (PLUME)