2007 Funded Access to the Sea Proposals

Scientific Sea-Trials for WHOI's New Deep-Diving AUV: Sentry
C. German, D. Yoerger, R. Brown

This proposal seeks to establish WHOI’s Sentry vehicle as the new international state-of-the-art for autonomous deep-diving investigations of the ocean floor. In preliminary deep-water trials in 2006, we established that the capabilities of Sentry will routinely surpass those of ABE - the vehicle that we had previously established as the world-leader in this field: Sentry will be able to dive faster, travel farther, and continue missions longer than ABE has ever been able to achieve. Building on this success, we have now secured funding from NSF to install a scientific payload on Sentry to carry out the cutting edge research for which it has been designed. That work is actively underway and will be completed in July 2007. The current request for ship-time, therefore, is to take this free-swimming robotic vehicle to sea aboard RV Oceanus in August-September 2007 and demonstrate its scientific community to our WHOI colleagues, to NSF and to the wider national and international community. Over the course of six days, we will follow a 5-dive program of sequentially increasing depth, duration and complexity culminating in a 12-

hour deep-ocean dive that mimics the full range of scientific uses for which Sentry has been designed. Because we also need time between dives for battery re-charging; data downloading, analysis and interpretation; and planning of subsequent missions, we will not need full use of the 6 days at-sea we have requested. Rather, our series of two-12hr dives would match very well with complementary seagoing projects. This project is strategically significant to WHOI because Sentry’s capability must be proven before we can migrate the vehicle into the National Deep Submergence Facility (Target date: January 2008). Our project also includes a strong educational component: we will support the research of two students and a post-doctoral fellow in the Deep Submergence Laboratory, including first at-sea research experience for both graduate students. Lastly, we will invite a science-journalism PhD student to sail with us as “science-writer-at-sea”.

A Test Mooring to Develop Wave Measurement Capabilities on WHOI Buoys
R. Weller, J. T. Farrar

Waves on the ocean surface are perhaps the most readily identifiable form of variability in the ocean, and ocean surface waves have an obvious impact on human activities. Real-time reporting of wave properties from surface buoys is one reason that the National Data Buoy Center’s web site has averaged more than 4 million hits per month since 2001 (Gilhousen and Hervey, 2001). The National Data Buoy Center (NDBC) and its parent organization, the National Oceanic and Atmospheric Administration (NOAA), see real-time reporting of surface wave properties as a key component of their operational mission in service of government and private users. In addition, the research community has a keen interest in better understanding the generation of surface waves, their effects on the upper ocean, and their role in air-sea exchange. These perspectives are echoed by the international Ocean Observing Panel for Climate (OOPC) and Joint IOC-WMO Technical Commission for Oceanography and Marine Meteorology (JCOMM). Clearly, we have a pressing need to develop the capability for measurement and real-time reporting of surface wave properties, especially when building proposals for the surface mooring component of a global ocean observing system, such as ORION, that has both research and operational objectives.

As part of an ongoing collaboration with NDBC, Weller, Farrar, and others in the Upper Ocean Processes (UOP) group of WHOI’s Physical Oceanography Department have been working to adapt for use on WHOI buoys technology that NDBC has developed for measurement of surface waves. NDBC’s wave package is ideal for our application because of its small size and low power consumption, and drawing on the technical expertise that NDBC’s scientists and engineers have developed during more than three decades of buoy wave measurements promises to significantly shorten the time and funding required to develop wave measurement capabilities on WHOI buoys. In return for NDBC’s guidance and provision of instruments, the UOP group will provide the wave data to NDBC in real-time, helping NDBC and NOAA to fulfill their operational mission. In addition to opening new avenues for WHOI scientists to examine the generation of surface waves in the open ocean and their role in setting the properties of the upper ocean, it is anticipated that capabilities for measurement and real-time delivery of surface wave data will make WHOI more competitive in maintaining and securing funding for long-term surface mooring deployments.

The wave measurement technique relies on measurement of the motion of the buoy as it is moved about by the waves. Since no buoy can perfectly follow the sea surface, accurate determination of the wave field from this information requires knowledge of the buoy’s response to surface waves. This proposal seeks time on the RV Oceanus to deploy and recover a test mooring at the Martha’s Vineyard Coastal Observatory where the motion of the buoy can be compared to independent measurements of the motion of the sea surface in order to “calibrate” the buoy and wave package.

Ensuring the Success of Future WHOI Deep-Ocean Mooring Deployments in Harsh Environments
R. Weller, J. T. Farrar

Multiyear time series of the physical properties of the upper ocean and of the atmosphere above are crucial to understanding how climate variability is mediated by air-sea exchange. The most direct and reliable measurements of these properties in the open ocean come from surface moorings, but it has long been a challenge to design surface moorings to withstand the harsh conditions found near the air-sea interface: the mooring and surface buoy may be subjected to strong winds, strong currents, large waves, vandalism, and impact by ships. The Upper Ocean Processes (UOP) group of WHOI’s Physical Oceanography Department has been addressing these challenges for over two decades, working with members of the Rigging Shop and Applied Ocean Physics and Engineering Department. The proven success of the mooring design of the UOP group has contributed to acquisition of long-term (indefinitely-funded) grants from the National Oceanic and Atmospheric Administration for the UOP group to maintain surface moorings at three “Ocean Reference Stations” that serve as a baseline for other climate observations and climate models.

As part of the National Science Foundation’s CLImate VARiability Mode Water Dynamics Experiment (CLIMODE), the UOP group deployed a mooring in Gulf Stream extension, an exceptionally harsh environment where currents can exceed 3 m/s (6 knots) and waves can exceed 13 m (>40 feet). Although the first of two one-year deployments was successful, the mooring broke free from its anchor three months into the second deployment.

We do not know why the CLIMODE mooring failed. WHOI colleagues graciously recovered the buoy as it drifted eastward in the Gulf Stream, but they were forced to cut the mooring line after the subsurface instrumentation had been recovered because of weather and operational constraints. Thus, the point of failure on the mooring has not been identified. Fortunately, the part of the mooring line below the point of failure is still anchored to the sea floor at the mooring deployment location, and recovery of this part of the mooring will allow us to understand the reason the mooring failed.

This is a proposal to use the RV Oceanus to recover the portion of the CLIMODE mooring remaining at the anchor site. Many sites of climatic interest, such as the Gulf Stream and high-latitude regions, are located in particularly harsh environments with strong winds, strong currents, and high seas. Understanding the reason for the failure of the CLIMODE mooring is vital to preventing similar failures and to ensuring that WHOI remains at the forefront of surface mooring design as moorings continue to be deployed in increasingly harsh environments of climatic importance.

Dust Control of Nitrogen Fixation and Community Structure in the Eastern Subtropical North Atlantic
P. Lam, T. Eglinton

In the past six years it has become evident that the diversity of marine nitrogen fixing cyanobacteria and of their habitats is much greater than previously thought. These recent advances highlight how little is known about the environmental and ecological controls on nitrogen fixation in the oceans. Recent studies have shown that Saharan dust additions to low nutrient waters of the eastern tropical North Atlantic stimulated nitrogen fixation by simultaneously supplying an external source of iron and phosphorus. Iron additions alone to these low nutrient waters did not have any effect. It is becoming clear that the availability of iron is important for community structure in both high and low nutrient environments, and further that the source of external iron addition can be important for community composition and export flux.

We seek funds and 4 days of additional ship time to add a water column sampling component to an existing coring cruise on the R/V Oceanus along the rarely visited NW African margin in July 2007. The ship’s zonal transect crosses large environmental gradients in dust, major nutrients, chlorophyll, temperature, and salinity and provides a perfect opportunity to examine the influence of major environmental gradients on general phytoplankton community structure. We will place particular emphasis on examining the effect of changing iron sources, determined using synchrotron x-ray analysis of large volume in-situ filtration samples, on the diversity of nitrogen fixers, determined using molecular genetic techniques. These samples will also provide the samples needed for the development of a lipid biomarker specific to nitrogen fixers that may serve as a proxy for past activity of these organisms based on studies of underlying sediments. The latter forms a central part of the dissertation research of James Saenz, a JP student.