Components

Main Hawaiian Islands Multibeam Bathymetry

This multiyear project has been funded by the School of Ocean and Earth Science and Technology and the Hawaii Mapping Research Group. They have undertaken the collection, processing, and visualization of all available bathymetry data for the Main Hawaiian Islands. The current public release (version 9) is the 3rd public release of the synthesis and will definitely not be the last.

Large Animal Tracking

The movement patterns of top predators are being tracked by a network of autonomous acoustic receivers (“listening stations”) deployed around the coast of O‘ahu and on Fish Aggregation Devices (FADs) that are anchored offshore. Tuna, marlin, sharks, and other animals that have been tagged with a transmitting device can be located and identified when they swim near the receivers. The tags used on these animals broadcast a unique identification code along with other information (for example, depth of the animal). In the future, it may be possible to relate the movement of these animals to the oceanographic conditions being measured by other parts of the HiOOS system. Additionally, this information can be used to model population dynamics of these important marine animals.

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Ecological Acoustics

Ecological Acoustics refers to a tool used by biologists to learn more about animals in the ocean and monitor areas of concern. Ecological Acoustic Recorders (EARs) are devices which listen for and record the sounds in a specific location (these sounds can be made by animals or by humans). For example, EARs record the sound of mammals such as whales and dolphins, as well as snapping shrimp, fishes, and the presence of marine vessels. EARs are a reliable, cost-effective tool for monitoring both biological processes and human activity in coral reef and other marine environments, even in remote locations. These recorders will be placed at the Kilo Nalu Cabled Observatory and in the Restricted Fishing Area of Makapu‘u. Ecological Acoustics allows us to learn more about the animals and ecosystems around Oahu and monitor protected areas of the ocean.

Coastal Imaging

The Coastal Imaging component of HiOOS uses various imaging technology to track changes in the coastline, including elevation and shape, and document the effects of incoming swell and high water levels on Waikiki and other beaches. There are several aspects to Coastal Imaging: 1) digital still images, 2) LIDAR (Light Detection and Ranging), and 3) digital video images. High resolution (8.5 megapixel) digital still images of the coastline are captured to reference additional spatial data and to document wave run-up. LIDAR technology emits a pulse of light and measures the time it takes the light to reflect off of a surface and back to the LIDAR. The time between emitting and receiving the light signal indicates the distance that the light pulse traveled before it bounced back to the LIDAR. When LIDAR is used to survey an area, it is possible to create a detailed map of the elevation of the land in the survey area. These maps are called Digital Elevation Models (DEMs). If surveys are repeated over the same area at two different times, it is possible to calculate the amount of sand that moved from one location or another within the survey area. The final aspect of Coastal Imaging is digital video imaging. A video camera on a Waikiki Hotel records, during daylight hours, the water run-up onto land (resulting from changes in waves and tides). Using the digital video and computer software, researchers are able to accurately document where and when the coastline is underwater. These various aspects of coastal imaging, combined, provide new information including digital elevation models (DEMs), GIS layers, erosion history, and wave and water level measurements. This contributes to more accurate predictions of the frequency and extent of coastal inundation and the potential effects of sea-level rise on O‘ahu.

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REMUS AUV

The REMUS (Remote Environmental Monitoring UnitS) is a compact Autonomous Underwater Vehicle (AUV) that moves through the water collecting information about the currents, temperature, salinity and fluorescence in the water. The REMUS also measures acoustic and optical backscatter which indicate the amount and types of particulate matter in the water — this can be used to detect poor water quality. In addition, REMUS is equipped with side scan sonar which can create images of the ocean bottom. The AUV navigates using GPS (Global Positioning System) which allows for operations in critical nearshore regions and in potential inshore pollutant source locations. The REMUS AUV is particularly well-made to operate in the nearshore environment. This AUV moves through the water using a battery-powered propeller and it can dive up to 100 m (328 ft) below the surface of the water. Researchers can communicate with the REMUS while at the surface using a WiFi connection. A typical survey can be completed in 6-8 hours (the maximum operating time of the REMUS is around 15 hours).

The REMUS AUV will be used to conduct surveys every two months of the O‘ahu’s south shore in order to have detailed snapshots of physical and chemical conditions. Additionally, event-driven surveys will be conducted if there is an episode of freshwater runoff, sewage spill or other event which could lead to pollution or poor water quality. These surveys give several types of information: 1) the spatial extent for potential pollutant coverage, 2) possibly identification of discrete “hot-spots” that may indicate isolated sources, and 3) estimates of how long the pollutant may remain in the within the survey region.

HF Radio

High Frequency (HF) Radio will be used for observing surface currents along the south shore of O‘ahu. HF Radio consists of 2 parts: a low power transmitter that sends radio waves toward the ocean and receivers listening to the signal that bounces off of ocean waves. HF Radio waves sent out toward the ocean surface interact with ocean waves and bounce back to the receivers. The HF Radio waves will only interact with a specific type of ocean waves — it has to be the right combination of the wavelength of the radio wave and the wavelength of the ocean wave. Ocean waves move at very predictable speeds and, therefore, the HF Radio waves bouncing off of the ocean wave have predictable patterns. When an ocean wave is moving through water that also has a current, the measured speed of the wave is different than what is predicted. The reflected HF Radio signal is modified by the direction and speed of waves that move through water with a current. The deviation from what is expected results in reflected HF Radio signals that are termed “Doppler-shifted.” Doppler shifted radio waves allow researchers to calculate the velocity and direction of the ocean current. The reflected Doppler-shifted HF Radio signal also contains information on wind direction and wave spectrum. Two radio transmitters, one at Koko Head and one at Barber’s Point, will be used to construct maps of currents and wave direction. These arrays of HF Radio transmitters and receivers will measure surface currents up to 125 km off shore of Oahu and send this data back to shore every 15 minutes.

Kilo Nalu Cabled Observatory

The Kilo Nalu Cabled Observatory, on the south shore of O‘ahu, near Kaka‘ako, provides a window into the nearshore coral reef physical, biological and chemical environment. This cabled observatory uses fiber optic cable to link sensors in the water to a shore station which houses the cable termination, power supply, and data server. Kilo Nalu consists of one central node (located at 10 m water depth) and 4 optional remote nodes at various water depths (10, 20, and 30 m). A variety of sensors at the central node provide wave height, period, and direction; current speed and direction; and water temperature, salinity, fluorescence (biota) and optical backscatter (turbidity). The data server in the shore station communicates wirelessly via the UH Ethernet and reports data every 20 minutes. These data are publicly available in near real-time on the internet. By continuously recording the physical, biological, and chemical characteristics of this popular area of the south shore of O‘ahu, the Kilo Nalu Cabled Observatory will help researchers establish baseline conditions and allow for early detection of changes in the water quality of this area.

Models

Data assimilating numerical models are an important component of HiOOS. Numerical models are one of the keys to creating products for three of the four HiOOS themes (four themes: Ocean State and Forecast, Water Quality, Coastal Resiliency, and Ecosystem Stewardship). Data assimilating numerical models combine environmental data and complex numerical equations to make predictions about environmental conditions now and in the future (nowcasts and forecasts). The focus will be on three types of regional models: 1) atmospheric, 2) wave, and 3) circulation. The core of HiOOS models will be a set of nested of ocean circulation models. Regional models will provide nowcasts and forecasts of ocean circulation, wave conditions, water level, and winds around the Hawaiian Islands.

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Water Quality Sensors

Water Quality Buoys

The HiOOS/PMEL water quality buoy is equipped to measure temperature, salinity, chlorophyll a, dissolved oxygen, carbon dioxide (CO₂) and optical backscatter (turbidity). This buoy will be located near one of the nearshore sensors to better constrain the water quality near the Ala Wai Outflow. The dissolved oxygen and carbon dioxide measurements will reveal important information about the balance of photosynthesis and respiration. Continuously sampling this area will give a record of baseline conditions of the chemical and biological environment for comparison when there are pollution events such as storm runoff or a sewage spill.

Nearshore Sensors

There will be four nearshore sensor packages located on the south shore of O‘ahu that continuously sample the water. Two of these sensor packages will be fully equipped to measure temperature, salinity, chlorophyll-a, and light transmission (turbidity). The remaining two sensor packages will measure strictly temperature and salinity. These packages will send data to shore every four minutes via cell phone. The area around Ala Wai Canal outfall will be instrumented with these 4 nearshore sensors which will allow early detection of changes in water quality, such as polluted runoff or a sewage spill. Additionally, because there are 4 sensor packages, the data gathered will provide estimates of the spatial extent of environmental conditions. With this early warning system in place, it will be possible to respond more rapidly with the appropriate precautions.

Two of four nearshore sensor packages have been deployed in the Ala Wai Canal. The first at the Waikiki Yacht Club, and the second at the Hawaii Yacht Club. These sensor packages measure temperature, salinity, chlorophyll-a, and light transmission (turbidity). Data are now streaming into a database. Plots of the Waikiki Yacht Club data may be viewed on the web: http://www.soest.hawaii.edu/hioos/hioos_ns-sensors.htm

Ocean Gliders

Ocean gliders are small, free-swimming vehicles that can cruise the ocean for up to 7 months gathering information about the temperature, salinity, fluorescence, and dissolved oxygen levels, and the absorption and scattering of light in the water by swimming and diving as deep as 1000 m (3280 ft) below the surface. A pressure sensor on the glider is able to record the depth throughout the dive. Because gliders are unmanned, they communicate with scientists on land when they are at the surface using an antenna on the end of the glider, and GPS satellites and Iridium satellites in space. When these gliders surface, they get instructions on where to go next and send back to shore the data that they’ve gathered. They can record the conditions of the ocean as they fly along a transect, or go up and down at a one location. When gliders communicate through the satellite, they can be instructed to change the direction they are swimming or change the way they are sampling.

Ocean gliders are relatively new, robot-like tools used to study the ocean. The US government started funding research and development of ocean gliders in the late 1990s. These gliders are very energy efficient because they have a special way of swimming that doesn’t require a propeller to push them through the water. Density is the mass per unit volume — or in other words how heavy something is relative to how big it is. For the gliders to rise to the surface or float, they have to be less dense than the water around them – that’s called buoyancy. To swim up or down, gliders change how big they are (change their volume) by pumping oil between a bladder that is outside the pressure case and a reservoir inside the pressure case. This is opposite to submarines which keep their volume the same but change their mass by adding or subtracting water from ballast tanks. The pressure case is also specifically designed to help change the buoyancy of the glider. The scalloped shape of pressure case allows the case to compress to match the compression of seawater as the glider dives further underwater. To change the direction the glider is moving, a weight (the battery) is moved forward, backward or sideways. Ocean gliders also have a very sleek outer shell (called a hydrodynamic shape) which allows them to move through the water without much resistance (water resistance is also called drag).

As a part of HiOOS, gliders provide very detailed information about the physical and chemical condition of the waters around the Hawaiian Islands. Additionally, these data get used in computer models to make predictions about currents.

Specifications

Weight: 52 kg (115 lbs)
Length: 1.8 m (5.9 ft)
Wing span: 1 m (3.28 ft)
Typical speed: 25 cm/s (~1/2 knot or ~1/2 mph)

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Waves and Water Level

The Waves and Water Level Component of HiOOS utilizes several types of technology including: wave buoys, pressure gauges, and satellite data. Several wave buoys are deployed around the Hawaiian Islands. These buoys report wave direction and height every 30 minutes via radio link to shore stations. Pressure gauges are devices that are secured underwater and an attached pressure sensor indicates the height of the water column above the sensor. These pressure gauges can be used to gather information about waves hitting the shoreline or they can be used as sea level stations (for monitoring overall sea level, tides, and harbor surge). Data from pressure gauges are communicated to shore every 10 minutes via satellite and wireless internet. The third aspect of Waves and Water Level is a system of satellites, called GOES satellites, which provide altimetry data. Using altimetry data, which indicates changes in sea surface height, it is possible to identify the presence of eddies (masses of water moving in a circular path) around the Hawaiian Islands. The Waves and Water Level component of HiOOS provides valuable information about harbor conditions, tides and sea level around Hawaii.

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