US ocean and polar sciences currently lacks an effective capability for routine under-ice inspection, sampling, and instrument manipulation, whether at the ice-ocean interface, in the water column of ice-covered oceans, or at the underlying high latitude ice shelves and coastal grounding lines. The US oceanographic community additionally lacks appropriate remotely operated vehicle (ROV) capabilities that can be regularly deployed from typical Global Class support ships. This is particularly challenging if they are to be accommodated alongside substantive multi-disciplinary research teams on the same vessel.
Polar seas and ice covered oceans present additional challenges. Conventionally tethered ROVs may be restricted in their placement, as the ice-resistant research ships from which they are deployed may be forced to drift with migrating ice over distances of >1 km in a matter of hours while over-the-side operations are underway. Consequently, such ROVs may not be able to stay on station in locations of specific interest, nor systematically survey across targeted sections of either the seafloor or, for other key science needs, the underside of floating ice-shelves.
A multi-institutional team of oceanographic engineers and scientists will use the lightweight fiber-optic tether and optical modem technologies that have recently been pioneered at WHOI Deep Submergence to provide solutions to both of these obstacles. Specifically, it is sought to develop a new polar remotely operated underwater vehicle, provisionally denoted PROV, capable of deployments in polar (including ice-covered) ocean regions traditionally considered inaccessible, except for the specific case of thick ice cover that can be accessed from vehicles and instrumentation designed for through-ice deployment.
In polar oceans, the vehicle will have a unique research role to play at the coastal seafloor, in mid-water, and at ice-ocean boundaries, ranging from studying heat-flow beneath the Arctic ice-cap, investigating melting beneath the terminal glacial outlets of Greenland and Antarctic ice sheets, investigating ecosystem function and productivity associated with the calving of icebergs, and annual onset and melting of sea-ice. The PROV will equip the polar ocean sciences research community with unique capabilities otherwise not available, enabling US polar and ocean scientists to continue to lead compelling and urgent research into one of Earth's most pristine and increasingly changing natural environments.
The Woods Hole Oceanographic Institution and collaborators from the Johns Hopkins University and the University of New Hampshire have developed for the polar science community a remotely-controlled underwater robotic vehicle capable of being tele-operated under ice under remote real-time human supervision. The Nereid Under-Ice (Nereid-UI) vehicle will enable exploration and detailed examination of biological and physical environments at glacial ice-tongues and ice-shelf margins, delivering high-definition video in addition to survey data from on board acoustic, chemical, and biological sensors. The vehicle employs a novel lightweight fiber-optic tether that will enable it to be deployed from a ship to attain standoff distances of up to 20 km from an ice-edge boundary under the real-time remote control of its human operators, providing real-time high-resolution optical and acoustic imaging, environmental sensing and sampling, and, in the future, robotic intervention. The goal of the Nereid-UI system is to provide scientific access to under-ice and ice-margin environments that is presently impractical or infeasible. Traditionally, operations in ice-covered waters have involved ice-breakers surveying and sampling by instruments lowered into the water column after breaking ice to access the underlying ocean. However, such operations are limited to ice thicknesses that can be broken through by a research vessel and, for example, cannot provide access beneath thick sea-ice and/or glaciers extending offshore from continents (e.g. Antarctica, Greenland). Ice-breaker based operations are also hindered by the difficulty in supporting tethered vehicles in moving ice conditions and only limited success has been achieved with AUV systems and also with fixed ice-penetrating moorings. The Nereid-UI addresses these constraints by using advances in undersea communications and robotic autonomy to enable the performance of complex tasks in ice-covered seas without perturbing the ice-ocean interface and up to a depth of 2,000 meters. It is designed to operate both untethered as an AUV for survey operations, and also as a self-powered vehicle employing an extremely small diameter optical fiber tether for tele-operated ROV sampling and intervention operations at extreme tether lengths (20 km or more). The vehicle fiber-tether design decouples the ROV motion from the iceconstrained surface ship, thus enabling ROV-like operations from icebreakers in moving ice as well as the ability to operate for distances as great as 20 km under ice shelves.