Dataset: Turbulence microstructure profiles

Name: Turbulence microstructure profiles collected during R/V Hugh R. Sharp cruise HRS2204 from Apr to May 2022
Published: 2024-12-16
Keywords: VMP, dissipation rate, turbulence, oceans

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Spatial Extent: N:41.764 E:-67.399 S:39.457 W:-72.266

Northeastern U.S. Continental Shelf

Temporal Extent: 2024-04-23 - 2024-05-01

Project:

Collaborative Research: The importance of particle disaggregation on biogeochemical flux predictions (Disaggregation)

Principal Investigator:

Matthew Rau (Pennsylvania State University, PSU)

BCO-DMO Data Manager:

Audrey Mickle (Woods Hole Oceanographic Institution, WHOI BCO-DMO)

Version:

Version Date:

2024-12-16

Restricted:

Validated:

Current State:

Preliminary and in progress

Turbulence microstructure profiles collected during R/V Hugh R. Sharp cruise HRS2204 from Apr to May 2022

Abstract:

These data include profiles of turbulence dissipation rate obtained from a Rockland Scientific VMP-250 deployed during a cruise on the Northeast Continental Shelf to study particle disaggregation. One cruise was completed aboard the R/V Hugh R. Sharp from 2022-04-21 through 2022-05-02 (HRS22-04), which visited a variety of stations and hydrodynamic environments associated with the Northeast Continental Shelf of the United States. Cruise stations where dissipation rate profiles were obtained ranged from Georges Bank and the Great South Channel near the Gulf of Maine, and Hudson Canyon near New York. These data were collected as part of a study to clarify the importance of hydrodynamic forces on the cohesion, aggregation, and breakup of marine particles. These data were collected by Dr. Matthew Rau (chief-sci) of the George Washington University.

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Methods & Sampling

This cruise visited eight stations on the Northeastern U.S. Continental Shelf. Latitudes and Longitudes provided per sample in the data, but general station descriptions are below. Turbulence microstructure profiles were only obtained at stations deep enough for free-fall profiling. These stations included Station 1, 2, 3, 4, and 8.

Station 1 - Station 3: Georges Bank near the Gulf of Maine. Approximate location was 41.7 N, 68 W. Samples acquired from 0 m to 25 m depths.
Station 4: The Great South Channel near the Gulf of Maine. Approximate location was 41.6 N, 69 W. Samples acquired from 0 m to 150 m depths.
Station 5: Only one CTD profile was taken before this station was aborted due to weather. No data acquired. Station location was 40.8 N, 70.5 W.
Station 6: Off the coast of Martha's Vineyard. Approximate location was 41.3 N, 70.5 W. Samples acquired from 0 m to 10 m depths.
Station 7: At the mouth of the Sakonnet River near Newport, Rhode Island. Approximate location was 41.5 N, 71.2 W. Samples acquired from 0 m to 10 m depths.
Station 8: Hudson Canyon near New York. Approximate location was 39.5 N, 72.3 W. Samples acquired from 0 m to 200 m depths.

Turbulence dissipation rate profiles were obtained following standard deployment techniques for the Rockland Scientific VMP-250 instrument. This instrument free-falls through the water column and measures shear spectra from piezo-electric probes. The instrument was deployed attached to a PID-02 free-fall winch and slightly negatively-buoyant tether to eliminate the influence of tether drag. Two shear probes (calibrated by Rockland within 2 mos of deployment) were installed on the instrument along with one temperature microstructure sensor. For deployment, the instrument was lowered into the water and held at the surface prior to release. The instrument was allowed to free-fall until close to bottom before bringing it back to the surface. the tether was manually fed out of the free-fall winch during the profile and one loop was maintained on the water surface to minimize tether drag on the instrument. Three profiles at each deployment were obtained prior to instrument recovery.

Problems/Issues

The time clock of the instrument would not hold its setting, likely due to a dead clock battery. UTC times and dates reported are ship-times at the beginning of deployment. Relative instrument time is also reported from the time the instrument was turned on at the beginning of the operation.

Data Processing Description

Shear profile data were processed using Rockland Scientific's Odas v4.4 Matlab library following the steps detailed in the manufacturer's TN_039_Dat_Processing_Manual_odas_v4.4d.pdf technical note. The odas library was used to convert high-frequency shear measurements from the profiler into shear spectra, to which a Nasmyth spectrum was fit to estimate dissipation rate. Data were processed using default settings except for the following:

Stations 1, 2, and 3: Dissipation rate was strong at these stations on Georges Bank with mean values approximately 10E-6 W/kg. Based on this dissipation rate and an instrument profiling speed of 0.7 m/s , the fft_length parameter was set to 0.714 s. The diss_legnth parameter to 2.142 s (3X the fft_length) and the overlap parameter set to 1.071. Finally, the ship wake was observed in the raw shear data to impact the upper 8 m of data so the min_profile_P parameter was set to 8 dbar.
Stations 4 and 8: Dissipation rate was weaker at these deep stations with mean values approximately 10E-9 W/kg. Based on this dissipation rate and an instrument profiling speed of 0.8 m/s , the fft_length parameter was set to 1.666 s. The diss_legnth parameter to 4.998 s (3X the fft_length) and the overlap parameter set to 2.499. Finally, the ship wake was observed in the raw shear data to impact the upper 8 m of data so the min_profile_P parameter was set to 8 dbar.

More Information about this dataset

Funding Sources

Funding Source	Award Number
NSF Division of Ocean Sciences	OCE-1948283

Deployments

Deployment	Synonyms	Start Date	Platform	Investigator
HRS2204	GoM22 cruise	2022-04-21	R/V Hugh R. Sharp	Matthew Rau (Chief Scientist)	data info

Instruments

Turbulence Profiler

Supplied Name: VMP-250

Supplied Description:

The turbulence microstructure profile used was the VMP-250 produced by Rockland Scientific, which was deployed using the free-fall PID-02 winch (AGO Environmental Electronics Ltd) and 6 mm, Dyneema core tether with a specific gravity of 1.38 g/cc.

Instrument Type

Generic Name: Turbulence Profiler

Generic Description:

A free-fall instrument that directly measures the vertical distribution of turbulent flow velocity in the water column.

Parameters

Date and time formats are described in python strftime() syntax.

Supplied Name	Supplied description	Supplied Units	Standard Name
Deployment_ID	Identifier of the Vertical Turbulence Profiler cast, formatted as Station#_deployment#, where deployment is incremented per station	unitless	sample
Station	Station number	unitless	station
Station_Deployment	Turbulence deployment number for station	units	cast
Station_Deployment_Profile	Profile number for each Vertical Turbulence Profiler deployment (1, 2, 3); VMP-250 completes three profiles per cast	unitless	cast
Cruise_Deployment	Turbulence deployment id where deployment number is incremented for whole cruise	unitless	cast
ISO_DateTime_UTC	ISO datetime when the sample was acquired in UTC Format: %Y-%m-%dT%H:%M:%SZ	unitless	ISO_DateTime_UTC
Date_UTC	UTC date on which the sample was acquired Format: %d-%b-%y	unitless	date
Time_UTC	UTC time when the sample was acquired Format: %H:%M:%S	unitless	time
Latitude	Ship's latitude when the sample was taken	decimal degrees	lat
Longitude	Ship's longitude when the sample was taken	decimal degrees	lon
t_rel	Time in seconds since the instrument was turned on	seconds	time_begin
p	Pressure in dbar	dbar	press
T	Temperature in deg Celsius as measured by the instrument conductivity-temperature sensor	degrees Celsius	temp
e	Dissipation rate of turbulence kinetic energy in watts/kilogram	watts per kilogram (W/kg)	eps

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Dataset: Turbulence microstructure profiles