Design and operation of automated ice-tethered profilers for real-time seawater observations in the polar oceans
Krishfield, Richard A.
Doherty, Kenneth W.
Frye, Daniel E.
Hammar, Terence R.
Kemp, John N.
Peters, Donald B.
Toole, John M.
von der Heydt, Keith
MetadataShow full item record
KeywordArctic instrumentation; Ocean profiler; Ice-based observatory; Louis S. St. Laurent (Ship) Cruise
An automated, easily-deployed Ice-Tethered Profiler (ITP) has been developed for deployment on perennial sea ice in polar oceans to measure changes in upper ocean temperature and salinity in all seasons. The ITP system consists of three components: a surface instrument that sits atop an ice floe, a weighted, plastic-jacketed wire-rope tether of arbitrary length (up to 800 m) suspended from the surface instrument, and an instrumented underwater unit that profiles up and down the wire tether. The profiling underwater unit is similar in shape and dimension to an ARGO float except that the float's variable-buoyancy system is replaced with a traction drive unit. Deployment of ITPs may be conducted either from ice caps or icebreakers, utilizing a self contained tripod/winch system that requires no power. Careful selection of an appropriate multiyear ice floe is needed to prolong the lifetime of the system (up to 3 years depending on the profiling schedule). Shortly after deployment, each ITP begins profiling the water column at its programmed sampling interval. After each acquired temperature and salinity profile, the underwater unit (PROCON) transfers the data and engineering files using an inductive modem to the surface controller (SURFCON). SURFCON also accumulates battery voltages, buoy temperature, and locations from GPS at specified intervals in status files, and queues that information for transmission at the start of each new day. At frequent intervals, an Iridium satellite transceiver in the surface package calls and transmits queued status and CTD data files onto a WHOI logger computer, which are subsequently processed and displayed in near-real time at http://www.whoi.edu/itp. In 2004 and 2005, three ITP prototypes were deployed in the Arctic Ocean. Each system was programmed with accelerated sampling schedules of multiple one-way traverses per day between 10 and 750-760 m depth in order to quickly evaluate endurance and component fatigue. Two of the ITPs are continuing to function after more than 10 months and 1200 profiles. Larger motor currents are observed at times of fast ice floe motion when larger wire angles develop and drag forces on the profiler are increased. The CTD profile data so far obtained document interesting spatial variations in the major water masses of the Beaufort Gyre, show the double-diffusive thermohaline staircase that lies above the warm, salty Atlantic layer, and many mesoscale eddys. Deployed together with CRREL Ice Mass Balance (IMB) buoys, these ITP systems also operate as part of an Ice Based Observatory (IBO). Data returned from an array of IBOs within an Arctic Observing Network will provide valuable real time observations, support studies of ocean processes, and facilitate numerical model initialization and validation.
Suggested CitationTechnical Report: Krishfield, Richard A., Doherty, Kenneth W., Frye, Daniel E., Hammar, Terence R., Kemp, John N., Peters, Donald B., Proshutinsky, Andrey, Toole, John M., von der Heydt, Keith, "Design and operation of automated ice-tethered profilers for real-time seawater observations in the polar oceans", 2006-06, DOI:10.1575/1912/1170, https://hdl.handle.net/1912/1170
Showing items related by title, author, creator and subject.
An inverse method for obtaining the attenuation profile and small variations in the sound speed and density profiles of the ocean bottom Rajan, Subramaniam D. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1985-05)The acoustic properties of marine sediments have a direct effect on the propagation of sound in the ocean. In the frequency range of interest (50 - 500 Hz) the sediment can be modelled as a fluid. Assuming horizontal ...
Estimating ocean heat transports and submarine melt rates in Sermilik Fjord, Greenland, using lowered acoustic Doppler current profiler (LADCP) velocity profiles Sutherland, David A.; Straneo, Fiamma (International Glaciological Society, 2012-11-01)Submarine melting at the ice-ocean interface is a significant term in the mass balance of marine-terminating outlet glaciers. However, obtaining direct measurements of the submarine melt rate, or the ocean heat transport ...
Casey, Kevin D. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1988-06)Two approaches to determining the ocean sound speed profile using measured acoustic modal eigenvalues are examined. Both methods use measured eigenvalues and mode dependent assumed values of the WKB phase integral as ...