Use of the High Resolution Profiler (HRP) in the Salt Finger Tracer Release Experiment (SFTRE)

The Salt Finger Tracer Release Experiment (SFTRE) was conducted in the tropical North Atlantic in 2001. The experimental area was east of Barbados and is characterized by thermohaline staircase features prevalent in the depth range of 200−600 meters. The goal of this experiment was to quantify the distribution and intensity of vertical mixing in a region of thermohaline staircases. Two cruises were required to accomplish this goal: one to survey with the High Resolution Profiler (HRP) and inject sulfur hexafluoride (SF6) tracer, and another ten months later to map the spatial distribution of tracer and obtain additional estimates of diffusive and turbulent mixing rates using the HRP. The first cruise of the SFTRE experiment took place between January 15 and February 12, 2001 on the R/V Oceanus, leg 365-2 (OC365). An XBT survey identified an area of robust staircases that became the injection site. Then 175 kg of SF6 tracer was injected in nine streaks in a layer with temperature of about 10°C. When the injection mechanism was being replenished, HRP profiles were made in the area of the tracer patch. The profiles yielded estimates of the mixing rates at the start of the experiment. Near the end of the cruise, water samples from the patch were used to map the actual tracer distribution immediately after deployment. The second cruise occurred between October 29 and December 4 on the R/V Seward Johnson, leg 01−12 (SJ0112). Its objective was to sample and map the vertical and horizontal distribution of tracer after ten months. The work completed included 172 CTD casts with chemical analysis performed on the water samples, and 165 HRP profiles. Despite covering an area of 500,000 nautical miles², only 50−60% of the tracer was found, suggesting higher than expected lateral mixing. The SFTRE included the deployment of a Moored Profiler. The profiles acquired by the MP provide background on the temporal variation of the temperature, salinity, and velocity fields where it was deployed. To share costs of personnel, the MP was deployed and recovered on cruises that followed ours, in conjunction with other mooring activities. The MP was deployed in February 2001 from R/V Oceanus and recovered by the R/V Knorr in April 2002. The program was a success, despite not fully delimiting the tracer distribution, because the observations allow more complete quantification of the mixing processes occurring in this region. The inferred mixing intensity was stronger and the influence of the thermohaline staircases more widespread than initially expected.Funding provided by the National Science Foundation under Grant No. OCE-0081502

Use of the High Resolution Profiler (HRP) in the Brazil Basin Tracer Release Experiment

On two recent cruises January 1996 and February 1997) aboard the R/V Seward Johnson, scientists from the Woods Hole Oceanographic Institution studied the deep mixing processes in the Brazil Basin. Two instrument systems were used in this experiment: the tracer injection and sampling system, and the High Resolution Profiler (HRP). The HRP measurements complement those obtained by the tracer sampling system, providing independent estimates of the turbulent and diffusive mixing occurrng in the study area. During the cruises, the HRP was used to make two zonal sections across the basin, provide data used to select the tracer injection site, and explore the jagged terrain near the Mid-Atlantic Ridge. The HRP component of the work at sea, an instrument description, data return and some preliminary results are presented in this report.Funding was provided by the National Science foundation through Grant No. OCE-94-1558

HRP II—the development of a new vehicle for studying deep ocean mixing

The High Resolution Profiler II (HRP-II), a unique, autonomous untethered, deep-ocean capable, profiling vehicle was designed and developed at WHOI during 2002-2003. During a vertical profile, it measures and records temperature, conductivity, pressure, horizontal and vertical components of velocity and turbulent-scale temperature and velocity gradient data. Great care was taken to minimize vibrations that would contaminate data from the microstructure sensors; the vehicle's movement is driven by graity, the body materials and shape were optimized for stiffness and no computer disk activity is allowed while profiling. All sensors are positioned to measure the same volume of water, and allow undisturbed flow to reach each one. The HRP-II was tested over the continental slope in January 2004. All aspects of vehicle function were successfully tested during seven profiles, the deepest of which was to 1583m. On one dive to 835m, termination was achieved at 17m above the bottom, close to the design specification. Several sensor and controller issues were identified that need to be resolved, but overall the vehicle performance on the test cruise was exceptional. The vehicle design specification, mechanical and electrical systems, sensors, controller, communications protocols, and testing of the HRP-II are documented in this report.Funding was provided by the National Science Foundation under Grant No. OCE-0118401 and the G. Unger Vetlesen Foundation

A graphical user interface for processing data from the high resolution profiler (HRP)

The High Resolution Profiler (HRP) is one of the only oceanographic instruments that is capable of measuring turbulent velocity and temperature fluctuations in the abyssal ocean. It is a unique device, and consequently specialized communications, data conversion and analysis software are employed to examine the data it collects. This document describes a major upgrade of the software and hardware systems used to process data from the HRP. The bulk of the conversion occurred in 1996 prior to the Brazil Basin Tracer Release Experiment (BBTRE). During the upgrade process, a Graphical User Interface (GUI) was designed and implemented for accomplishing routine HRP data processing tasks.Funding was provided by the National Science Foundation through Grant No. OCE-94- 15589

Fine- and microstructure observations at Fieberling Guyot : R/V New Horizon cruise report

This report describes fine- and microstructure profile data taken on a cruise to Fieberling Guyot, a seamount in the northeast subtropical Pacific Ocean. The work performed at sea, instruments used, data return and processing procedures will be summarized here. This cruise took place between March 4 and March 28, 1991 on the R/V New Horizon. and was part of the interdisciplinary Accelerated Research Initiative (ARI) for Abrupt Topography sponsored by the Office of Naval Research. An overall goal of the ARI was to understand the physical, biological, and geological processes occurring near a seamount. The scientific objective of the Seamount Mixing Cruise was to collect data describing the oceanic fine-scale velocity and density fields, as well as the related turbulence and mixing in the vicinity of the seamount. The High Resolution Profiler (HRP) was deployed 95 times above and around the seamount. As well, two test dives were conducted on the way to the site, and eight deployments completed in deep basdins off the southern California coast before returning to port. The near-synoptic surveys of the seamount were completed with the deployment of 128 Expendable Current Profilers (XCP's). The temperature field of the upper 760 meters of water within a 50 kilometer radius of the seamount was mapped using 144 Expendable Bathythermographs (XBT's).Funding was provided by the Office of Naval Research through Grant No. NOOOI4-89-J-1073

Cruise report-Oceanus 218, March 20-April 9, 1990 : warm ring inertial critical layer experiment (WRINCLE)

R/V Oceanus Cruise 218 (OC218) departed Woods Hole March 20,1990 for 20 days of work in a Gulf Stream Warm Core Ring. The scientific objective of the Warm Ring Inertial Critical Layer Experiment (WRINCLE) was to study the phenomenon of inertial-internal wave trapping in anticyclonic rings and the associate mixing. High Resolution Profiler (HRP) casts provided fine- and microstructure data and the Richardson Number float and eXpendable Current Profiler (XCP) surveys provided velocity and density finestructure measurements. During the time R/V Oceanus was in and around the ring, 78 HRP drops to 1000 m were completed, and data from 55 XCPs, 26 Conductivity Temperature and Depth Profiler (CTD) casts, and 59 eXpendable BathyThermograph (XBTs) were logged. The free-drifting Richardson Number float (RiNo) acquired data for eleven days in ring center. This report documents the work performed at sea, and summarizes some of the data collected.Funding was provided by the National Science Foundation through Grant No. OCE 89-11053

Cruise report : Oceanus 250 Leg 4 High Resolution Profiler survey for the North Atlantic Tracer Release Experiment: (NATRE), March 25-April 24, 1992

This report describes fine- and microstructure profile data taken on R/V Oceanus cruise 250 leg 4, between March 25 and April 24, 1992. During this cruise, an area of the Canary Basin near the Subduction Experiment's central mooring was surveyed with the High Resolution Profiler (HRP). The goals of the survey were to describe the hydrographic properties of the water adequately to recommend a location for the North Atlantic Tracer Release Experiment (NATRE) tracer injection, and to characterize the microstructure for comparison with the NATRE results. The work performed at sea, instrumentation, data return and processing procedures will be summarized in this report.Funding was provided by the Office of Naval Research through Grant No. N00014-92-1323

Turbulence and waves over irregularly sloping topography : cruise report - Oceanus 324

This report documents the work of R/V Oceanus cruise 324, which occurred during May of 1998. This cruise was the field component of the Turbulence and Waves in Irregularly Sloping Topography (TWIST) program. TWIST was part of the Littoral Internal Wave Initiative (LIW) supported by the Office of Naval Research. The objective of TWIST was to sample the background, internal wave and turbulence properties on the Continental Slope in the Mid-Atlantic Bight. Previous investigations have revealed strongly enhanced finescale internal wavefields and much more energetic turbulence due to internal wave breaking above topographic roughness associated with the Mid-Atlantic Ridge. So, an area of steeply sloping ridges and troughs running perpendicular to the continental slope near 36˚34'N, 74˚39'W was chosen as the site of the observational program due to its topographic similarity to the Mid-Atlantic Ridge. Fíve instrument systems were employed to make observations during this cruise: the High Resolution Profier (HRP), three Moored Profiler (MP) moorings, a Lowered Acoustic Doppler Current Profiler/Conductivity, Temperature, Depth (LADCP/CTD) rosette, eXpendable Current Profilers/eXpendable CTD (XCP/XCTD), and finally, the shipboard ADCP. The data from these instruments (more than 1100 full depth profiles) provide adequate spatial and temporal resolution to describe the finescale and turbulent processes observed.Funding was provided by the Office of Naval Research under Grant No. N00014-97-1-0087