Dataset: MCTD Lake Michigan 2017, 2018 & 2019

Name: Microstructure profiles at Station AT55 in Lake Michigan from 2017, 2018 and 2019.
Published: 2021-08-17
Keywords: microstructure, Lake Michigan, hypolimnion, lake, turbulence, dissipation, mixing, turbidity, chlorophyll, CTD, oceans

Cite This Dataset

DOI:10.26008/1912/bco-dmo.768011.2

Spatial Extent: N:43.069917 E:-87.753217 S:43.069917 W:-87.753217

Temporal Extent: 2017-08-01 - 2019-05-14

Project:

Collaborative Research: Regulation of plankton and nutrient dynamics by hydrodynamics and profundal filter feeders (Filter Feeders Physics and Phosphorus)

Principal Investigator:

Cary Troy (Purdue University)

Co-Principal Investigator:

Harvey Bootsma (University of Wisconsin, UW-Milwaukee)

David Cannon (Purdue University)

Qian Liao (University of Wisconsin, UW-Milwaukee)

Contact:

Cary Troy (Purdue University)

BCO-DMO Data Manager:

Karen Soenen (Woods Hole Oceanographic Institution, WHOI BCO-DMO)

Version:

Version Date:

2021-08-17

Restricted:

Validated:

Yes

Current State:

Final no updates expected

Microstructure profiles at Station AT55 in Lake Michigan from 2017, 2018 and 2019.

Abstract:

Turbulent microstructure profiles were collected near Milwaukee, WI, during 2017 (August 1 - August 16), 2018 (April 5 – April 20), and 2019 (May 13 - May 14) at a 55m depth site. Microstructure measurements were collected using an RSI MicroCTD (Rockland Scientific International, Inc.), which measures velocity shear, temperature, turbidity, and chlorophyll concentrations. High resolution velocity shear (512 Hz) measurements were used to estimate turbulent kinetic energy dissipation throughout the water column. Microstructure profiles were collected during fair weather conditions on each day of sampling.

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Archival Copy

Version Date	Archive	Persistent Identifier	Date Assigned
2021-08-17	Marine Biological Laboratory/Woods Hole Oceanographic Institution Library (MBLWHOI DLA)	10.26008/1912/bco-dmo.768011.2	2021-08-20
2019-05-15	Marine Biological Laboratory/Woods Hole Oceanographic Institution Library (MBLWHOI DLA)	10.1575/1912/bco-dmo.768011.1	2019-05-20

Description

Methods & Sampling

Microstructure profiles were taken over 3 years:

2017: 176 microstructure profiles were collected over six days (August 1st, 2nd, 9th, 10th, 15th, and 16th).
2018: 129 microstructure profiles were collected over three days (April 5th, 12th, and 20th).
2019: 78 microstructure profiles were collected over three days (May 13th and 14th).

Measurements were collected using an RSI MicroCTD (Rockland Scientific International, Inc.) which sampled shear and temperature microstructure at 512Hz, free-falling at a velocity of 0.8 m/s (vertical resolution: ~1.5mm). Shear microstructure was analyzed to obtain turbulent kinetic energy dissipation (see data processing). Velocity shear was measured using two velocity shear probes (RSI; accuracy: 5%) oriented perpendicularly to collect orthogonal shear components. Microstructure temperatures were collected using 2 FP07 probes (accuracy: 0.005 ), with the resulting measurements averaged to produce the single temperature estimate included in the attached files. Turbidity (accuracy: 2%) and fluorescence (accuracy: 1%) measurements were collected using a JAC-CLTU sensor (JFE Advantech Co., Ltd).

Microstructure profiles were collected manually by letting the instrument free fall through the water column. Profiles were timed and manually stopped to prevent the instrument from crashing into the bed and damaging sensors.

Data Processing Description

Data were downloaded from the instrument and converted to physical units using Matlab software provided by the manufacturer. The energy spectra of vertical velocity shear were used to estimate turbulent kinetic energy dissipation using a combination of power spectral density function integration and Nasmyth empirical spectrum fitting (manufacturer-provided algorithms; see attached TN_028_Dissipation.pdf).

Energy spectra were calculated from 2s (1024 sample) measurement intervals overlapped by 50% (vertical resolution: 0.8m), with corrections for both instrument accelerations and probe-induced spatial averaging (see attached TN_028_Dissipation.pdf).

The mean absolute deviation (MAD) was used to identify and discard all observed spectra that were effected by anisotropy or deviated significantly from the shape of the model spectrum, with a rejection criteria of MAD>2(2/d)1/2, where d is degrees of freedom of the observed spectra.

BCO-DMO Processing Notes:
- added conventional header with dataset name, PI name, version date
- modified parameter names to conform with BCO-DMO naming conventions
- added ISO_DateTime_UTC column with converted DOY_GMT into ISO 8601 format.
- added "profile_name" column to contain information about the name of the profile.
- added columns 'DOY_GMT', 'latitude', 'longitude' from supplementary file, using the "profile_name" column as the join key.

Data Files

File
profiles_all.csv (Comma Separated Values (.csv), 3.57 MB) MD5:9d90ea1891a06b77510388781232a117 Primary data file for dataset ID 768011

Supplemental Files

File
RSI Technical Note 028 filename: TN_028_Dissipation.pdf (Portable Document Format (.pdf), 1.02 MB) MD5:4d437a4886c702772472fce47ea0030e Calculating the Rate of Dissipation of Turbulent Kinetic Energy

More Information about this dataset

Funding Sources

Funding Source	Award Number
NSF Division of Ocean Sciences	OCE-1658390

Deployments

None available yet

Instruments

CTD - profiler

Supplied Name: RSI MicroCTD (Rockland Scientific International, Inc.)

Supplied Description:

Instrument Type

Generic Name: CTD - profiler

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/130/

Generic Description:

The Conductivity, Temperature, Depth (CTD) unit is an integrated instrument package designed to measure the conductivity, temperature, and pressure (depth) of the water column. The instrument is lowered via cable through the water column. It permits scientists to observe the physical properties in real-time via a conducting cable, which is typically connected to a CTD to a deck unit and computer on a ship. The CTD is often configured with additional optional sensors including fluorometers, transmissometers and/or radiometers. It is often combined with a Rosette of water sampling bottles (e.g. Niskin, GO-FLO) for collecting discrete water samples during the cast.

This term applies to profiling CTDs. For fixed CTDs, see https://www.bco-dmo.org/instrument/869934.

Parameters

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

Supplied Name	Supplied description	Supplied Units	Standard Name
pressure	average pressure at measurement location	decibar (dbar)	press
temp	average temperature	degrees Celsius	temp
S2	average total velocity shear (S2=[dU/dz]2+[dV/dz]2	1/s2	no_bcodmo_term
turb	average turbidity	FTU	turbidity
chlor	average fluorescence	ppb	fluor
dissipation	turbulent kinetic energy dissipation calculated from shear signal	Watts per kilogram (W/kg)	no_bcodmo_term
profile_name	profile name extracted from submitted file name	unitless	cast
DOY_GMT	time corresponding to each profile name. Times are taken as the average of measurement times for a given profile. Time units are days in GMT.	unitless	no_bcodmo_term
latitude	latitude with positive values northward	decimal degrees	lat
longitude	longituide with positive values eastward	decimal degrees	lon
ISO_DateTime_UTC	Date and time formatted following ISO8601 convention	unitless	ISO_DateTime_UTC

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Database

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Dataset: MCTD Lake Michigan 2017, 2018 & 2019