These application stories of tilt current meters and data loggers highlight how the instruments are used in the field to offer insight into deployment applications or methods.
A dozen Tilt Current Meters (TCM-1’s) were deployed in the Florida Keys and South East Florida in coral reef habitats. Lew Gramer, Assistant Scientist with NOAA & The University of Miami's Cooperative Institute, said of the tilt current meters, “they are especially useful because they can show how the water flows over the coral”.
The TCM’s were first deployed in 2015 and are cycled through a 6-month time series to study temperature and flow. The research team led by Stephanie Rosales and Dana Williams is investigating how water flow is related to the health of the coral. “ADP’s generally miss the boundary and there is a need for accurate temperature and velocity”, Gramer noted, “The more traditional instruments measure whole water columns and profiles but generally miss coral where they live and experience the flow. Because the TCM’s are very sturdy, less expensive and easier to deploy they can be packed more densely in areas that are topographically complex”. The team is also looking at any rapid, high frequency variability events and effects on coral reefs to learn how coral reefs can thrive.
The tilt current meters offer ease of use and affordability for this type of research. “They are very easy for divers to deploy with 12x12 paving stone to anchor them", Gramer added. “With the TCM's you can afford to have another one ready to replace right away and to swap out instruments and data when the battery is limited."
Here is a quick video of the TCM set up in the environment:
Lowell Instruments’ sensors were used in deep-sea loggers to study hydrothermal systems at Mid-Ocean Ridges (MOR)s. Dan Fornari from the Woods Hole Oceanographic Institute and Thibaut Barreyre from the University of Bergen-Norway made improvements to WHOI-MISO loggers with the addition of Lowell Instruments’ attitude and temperature sensors in the logger housing for use in their research. The vent fluid and attitude data loggers are manufactured by EP Oceanographic, LLC and can provide vent time-series temperature measurements. The sensors “determine any correlative motion of the logger with recorded temperature anomalies”, Fornari said, and “provide significant information about whether the temperature perturbations are caused by fluid flow variations or subtle to abrupt motions of the logger due to chimney cracking, collapse, or ground motion”.
The high-temperature loggers have been used by many U.S. and international scientists studying vents globally, including sites at: Axial Seamount and Main Endeavour, Lucky Strike, Lau Basin, and East Pacific Rise 9-10°N. By studying hydrothermal vent systems at the Mid-Ocean Ridges, Fornari and Barreyre are hoping to gain a better understanding of sub-surface processes including their effects on hydrogeology and shallow circulation patterns of hydrothermal flow in the young ocean crust. Additionally, the data provided by the loggers will be used to study fluid-dynamic interaction and impacts to local ecosystems.
Fornari explained, “Although hydrothermal systems were initially conceptualized as steady-state flow environments, field-based observations indicate that flow rates and temperatures may vary over a wide range of spatial and temporal scales. These observations demonstrate that hydrothermal systems respond to sub-surface processes such as earthquakes, magmatic activity, dissolution/precipitation of hydrothermal minerals, and the poroelastic response to tidal loading.”
For more information about their research and use of loggers:
Oceanography article by Dan Fornari, et al.
Jeff P. Donnelly from the Woods Hole Oceanographic Institution and his team are researching blue holes in the Caribbean to connect the dots on climate history and hurricane activity. Tilt current meters were used to aid in the research and were deployed long-term all over the Caribbean, specifically in several blue holes in the Bahamas, Jamaica, Turks and Caicos.
“Coring is a key component of our fieldwork and our target sites are often blue holes, back barrier ponds, lagoons or other geologic depressions protected by a shallow sill that serve as sedimentary bowls. This geometry is important as the sediment inside the bowl remains undisturbed during storm events and serves as a time capsule”, said Nicole d’Entrement, Research Assistant for the WHOI team. “Tilt [current] meters are deployed every time we travel to a site of interest. The majority of our research sites are remote and hard to reach so we retrieve the data annually or biannually”.
Tilt Current Meters (TCM’s) were used to determine where deposited sediment is transported from and how the water on the sill is behaving during a storm. “In combination with other sensors we can tell how much water is piled onto the sill and the direction that it is coming from. It’s important data to collect and would be difficult to measure without a tilt [current] meter”, d'Entrement said. The benefits of TCM’s are, as d'Entrement noted, that they “are light, easy to transport, and resilient. We recovered data off of our tilt [current] meter that survived Hurricane Irma in 2017.”
By applying a “multi-site/multi-environment approach to reconstruct past intense hurricane landfalls”, Donnelly and his team are able to construct “a comprehensive picture of hurricane activity in the North Atlantic…to distinguish changes in hurricane genesis and changes in hurricane track.”
For anchoring, the TCM’s lanyard was tied to a cinder block and a ground line was attached to a second block. The second block was used to mount any additional sensors (thus avoided the possibility of interference between the devices). The assembly was then lowered from a boat and a diver was used for final positioning. You can find a brief video showing their TCM deployment setup below.
For more information and links to the research:
Christina Bonsell, a PhD student at the Dunton Lab at the University of Texas in Austin has been using tilt current meters or TCM1’s since 2015 and deployed multiple meters in the field at Stefansson Sound and for The Beaufort Lagoon Ecosystems LTER (member of the NSF LTER Network). Her research team headed by Ken Dunton, is looking at a kelp bed community located in the central Alaska Beaufort Sea coast, an isolated part of the Arctic Ocean. The Boulder Patch is a biodiverse marine environment that is rich in the kelp Laminaria solidungula.
The TCM’s were attached to 10-pound dive weights in varying depths and areas of a large lagoon where the maximum depth is 10 to 12 meters. Bonsell said, “the tilt current meters are less expensive, very easy to deploy, easy to retrieve via scuba divers and relatively small”. The data that is retrieved will look at “current dynamics in the lagoon both in spatially different depths within and some more exposed areas of the lagoon where there is more exchange with the open ocean”. It will help to understand how currents are different over space and time. The meters were deployed every 12 months so the data will be retrieved again in July or August.
To learn more about their research on sea kelp and published data:
Stanford University undergraduate students got to work with hands-on field tools under the direction of two lead instructors including Stephen Monismith, the Obayashi Professor in the School of Engineering. In the Republic of Palau, students donned snorkeling gear and collected data on the coral reefs and its surrounding ecosystem.
Heidi Hirsh was one of the participants of the Ecology and Management of Coral Reefs of Palau program seminar. She deployed several tilt current meters (TCM-1's) that "coupled biogeochemical and hydrodynamic measurements to provide a high-resolution record of seagrass productivity”. A meter was deployed at either end of a 571m seagrass bed in conjunction with Acoustic Doppler Velocimeters (ADVs) and Acoustic Doppler Profilers (ADPs). They were then used "to determine the dominant current flow direction and velocity at either end of the seagrass bed”.
The TCM’s were deployed in the seagrass for less than a month while some TCM’s were deployed for longer periods for other student projects. “In order to calculate oxygen flux (net community production, NCP) over the seagrass bed it was important to show that there was tidally driven uniaxial current flow over the bed which allowed us to determine NCP using an ‘upstream-downstream’ approach (any changes in pH or dissolved concentration over the bed were due to seagrass productivity along the transect line)“, Hirsh said.
The meters had been attached to cinder blocks with a line for easier retrieval. “The tilt current meters were very easy/straightforward to program and deploy. We did not have to worry about the orientation of the meter or having it deployed exactly level as we do for the ADVs and ADPs.”
Because of the portability of TCM’s, Hirsh said, “transportation was also much easier. We could pack the current meters (buoyant part) in a regular suitcase and hand carry the loggers on the plane. Our other instruments required their own cases which quickly becomes expensive for field work.”
To learn more about the study and coral reef research in Palau:
USGS Biogeochemist John Pohlman and Texas A&M Postdoctoral Scientist David Brankovits, along with an international research team, studied submerged flooded cave systems of Ox Bel Ha in the Northeastern Yucatan. The team discovered an ecosystem in the groundwater where living organisms were feeding on methane as a primary source. “It is an interesting way that life is able to subsist in an extreme environment”, Pohlman said.
Deep in the underwater caves Tilt Current Meters (TCM-1's) were deployed in different areas of the cave system. They were secured to dive weights to measure the current velocity of two distinctly different water columns: shallow, relatively fresh water that is loaded with dissolved methane and deeper, salt water below with low methane. The current meters are retrieved every six months. The data that is collected will help to understand the hydrodynamics of the differing water masses and how they are mixing. According to Pohlman, the TCM’s were “very easy to install and super reliable.” The economical meters were easy to deploy by divers and were left in locations where there was a risk of loss or theft. The meters were configured to collect 1-minute current and temperature records for the 6-month deployments.
"The TCM’s are able to provide the data we require to answer the scientific questions we have”, Pohlman said, “Therefore the current measurements allow us to quantify how the ingredients for the life of bacteria exist.”
To learn more about the study click here:
David Brankovits likes using the meters so much that he and his colleagues made a video featuring the TCM-1 for us. You can view it here: Youtube
In May of 2017 researchers from Temple University, Scripps Institution of Oceanography, Cal Tech, Occidental College, and the University of Rhode Island were on board the RV Atlantis from Woods Hole Oceanographic Institution. The team studied methane seeps off the Pacific Coast of Costa Rica, in the methane-rich Costa Rica Margin. Using the Alvin submersible Chris Roman, Associate Professor at The University of Rhode Island, deployed four tilt current meters (TCM-3’s) on the seafloor. They were “to study variability and steady flow in the bottom currents and to get a sense of what was happening to currents”. The researchers were approximately 3,000 meters deep in the ocean and used the deep water TCM's that were suitable up to 4,500 meters. The TCM's were left at the bottom of the seafloor with 10-pound dive weights in varying locations to record data for over a year. They are due to be retrieved in October of 2018.
“The benefits of using these TCM’s are its affordability and ease of use. You can use multiple meters in several areas to get better data more quickly”, Roman said, “and the length of time that it can be [deployed] gives you a better time series.”
Especially relevant to how methane influences the sea, Roman said, “we want to understand the impact of methane seeps on local communities”.
To learn more and to follow the ongoing ROC HITS project click here:
We look forward to telling you more about the TCM’s that are retrieved later this year.
Right in our neighborhood of Falmouth, Ward Aquafarms has used four tilt current meters (TCM-1’s) to evaluate sites for bay scallop aquaculture. “We have four farms participating, so the deployment depth is different on each one. Two of the farms are in about 20' of water, one farm is in 8' of water, and the final farm is intertidal, so the cage and flow meter go dry and sit on sand twice a day at low tide”, Dan Ward, Owner of the business said.
The tilt current meter was tied to a cage with a rope secured to a zip tie and thrown off the side of a boat. A meter was deployed at each farm for either 4 or 8 months to collect data on velocity and temperature. Ward has partnered with Cape Cod Cooperative Extension using research and technology to find best practices for growing and sustaining bay scallops. The project focuses on “four different environments on four different commercial farms ranging from intertidal to subtidal and estuarine to open-ocean” to determine optimal conditions for growing bay scallops locally and to expand aquaculture on the Cape. More data is currently being collected so check back for more information on the project.
The focus of a study led by an international team including Ph.D. student Brandee Carlson from Rice University was sediment delivery of abandoned distributary channels and surface water connections. River diversions in the Huang He cause channels that line the coast of the sea to transition to tidal mud flats. The sediment input from tides accumulates in these abandoned channels. Carlson and her team have used tilt current meters (TCM-1 and TCM-4) since 2016 to look at how sediment accumulation affects delta dynamics. TCM’s were deployed along the delta bed by placing them on the mud flats tethered to concrete blocks. The devices will determine the bottom speed and direction to help understand sediment movement through the river and along the delta.
The TCM’s were effective in the delta, Carlson said, “because you could place them a few meters deep in mud flats at intertidal elevations that get inundated with only half a meter of water in fair weather”. It was co-located with an acoustic meter to do comparison data. “They are really easy to work with and compared to the cost of acoustic meters you basically have an instrument which can get the time series you need with more points at the field site which is really important for this study. It was instrumental in looking at ... [changes] over space and time.”
The TCM’s held up considerably in a sediment laden environment where there is potential for the devices to become buried. In the summers they were deployed for 6-week intervals and in the winter for 2 weeks. With tidal flats changing all the time, the data was “faithfully recorded”, according to Carlson. “The advantage of these meters is that you can be bolder with the instrument placement.”
The research will help to understand how abandoned deltaic distributary channels fill with sediment and how they evolve. On a broader scale, it will help to see how channels from diversions, both natural and engineered, compare and also look at the seasonal component of sediment transport. In addition, the study will help to build predictive models for coastline stability.