Ocean Mixing and Stirring  
  Principal Investigator: Dr. Miles A. Sundermeyer
msundermeyer@umassd.edu • 508-999-8892
University of Massachusetts Dartmouth
School for Marine Science and Technology
 
 

Home/Overview

Publications
People

* ** Graduate Research
    Assistantships
    Available
**

Teaching:

* Courses Taught

Research:

* Lidar Studies of Small- Scale Lateral Dispersion - LatMix
* 3D Dye Mapping using Airborne Lidar - Florida 2004 Pilot
* Lab Studies of Stirring by Small-Scale Geostrophic Motions
* Numerical Simulations of Vortical Mode Stirring
* Coastal Mixing & Optics (CMO)
(... More links coming soon!)
* The North Atlantic Tracer Release Experiment (NATRE)
(Links coming soon!)

Additional Links
* M. Sundermeyer's CV (PDF)

 

© 2005 Miles A. Sundermeyer (msundermeyer@umassd.edu)
Note: Please do not use the data, text, or images contained on this site without prior permission.

Coastal Mixing & Optics (CMO) Dye Studies
PIs: J. R. Ledwell and T. F. Duda
Grant Title: Tracer Studies of Mixing in Stratified Coastal Waters
Funding Agency: Office of Naval Research
Award: $965,065

Project Background

A study of stirring and mixing in density-stratified waters on the continental shelf was conducted as part of the ONR funded Coastal Mixing and Optics Experiment. Fluorescent dye and drogues were released, and their subsequent dispersion measured to determine rates of diapycnal diffusion, lateral dispersion, and lateral homogenization over 3 to 5 day periods.

Temperature and conductivity were measured simultaneously with the dye at 2 cm resolution along with the dye measurements from a towed body in order to characterize the spatial scale of patches of enhanced gradients. Dissipation rates of temperature variance were inferred from these measurements and compared with the diapycnal diffusivity estimated from the dye dispersion in order to test the Osborn-Cox relation proposed between the two. Shear was also measured by shipborne ADCP throughout the experiment at 2 m resolution.

Dissipation rates of temperature variance and of turbulent kinetic energy were measured directly by profiler deployments in work proposed separately by Neil Oakey of Bedford Institute of Oceanography, on alternate watches with the dye surveys to test the Osborn-Cox relation, as well as the relation between diapycnal diffusion and kinetic energy dissipation proposed by Osborn. Detailed hydrographic measurements and measurements of the Reynolds stress and an approximation of the heat flux were made continuously throughout the experiment from a tripod-based array of instruments by Trowbridge and Williams. These experiments were further embedded in the mooring array proposed by Lentz, et al., which provided a 9 month time series of the meteorological forcing and of the current field on 30 km scale, with 5 m vertical resolution.

Dye-Release Experiments

Fluorescent dye and drogues were released in order to determine rates of diapycnal diffusion, lateral dispersion, and lateral homogenization over 3 to 5 day periods. Five releases were performed in late summer when a pycnocline was well established. Four of these were at mid-depths and the fifth just above the bottom boundary layer (see table and figures below).

- dates dye injection lat, lon target density
(kg/m3)
target depth
(m)
sampling
surveys
experiment 1 Sept 1995 rhodamine 40.44 N, 70.49 W 25.20 40 2
experiment 2 Sept 1996 rhodamine 40.46 N, 70.32 W 24.063 35 3
experiment 3 Sept 1996 fluorescein 40.47 N, 70.32 W 24.30 46 3
experiment 4 Aug 1997 rhodamine 40.48 N, 70.33 W 24.6 18 3
experiment 5 Aug 1997 fluorescein 40.48 N, 70.49 W 26.14 62 3

The study site was approximately 100 km south of Martha's Vineyard, MA in the region known as the "mud patch" (see figures). For each experiment, a single streak of dye was released along an isopycnal surface using a towed injection system. Along with the dye, three to six drogues were also released at the target depth and tracked via ARGOS transmitters. The drogue positions were used along with near real-time shipboard ADCP observations both to assist in locating the dye patch and as an aid to planning sampling strategies during the dye surveys. ADCP data were also logged for later analysis.

1995 rhodamine experiment 1996 rhodamine experiment
1996 fluorescein experiment 1997 rhodamine experiment
1997 fluorescein experiment

Subsequent to each dye release, three-dimensional surveys of the dye patch were conducted using a sampling sled that was tow-yo'd behind the ship at 2-4 kts. The winch operated at speeds between 30-60 m/min, which provided a vertical profile every 100-200 m along the ship track. The sampling system included either a rhodamine or fluorescein fluorometer (depending on the type of dye released), a chlorophyll fluorometer, and a Seabird CTD. These instruments sampled at rate of 6 Hz, providing an average vertical resolution of 10 cm.

Hydrographic sections extending across the shelf were made at the beginning and sometimes the end of each cruise. These stations provided detailed descriptions of local conditions and were used to determine where to inject the dye and to help plan subsequent dye sampling strategies. Meteorological data were also logged for each of the cruises using the shipboard Improved Meteorological (IMET) package. In addition, data were obtained from nearby buoys of the National Oceanic and Atmospheric Administration / National Data Buoy Center (NOAA / NDBC).

Results from these experiments can be found in the following publications, and in the links in menu to the left.

 

Publications

Sundermeyer, M. A., J. R. Ledwell, N. S. Oakey, and B. J. W. Greenan, Stirring by Small-Scale Vortices Caused by Patchy Mixing. J. Phys. Oceanogr., 35 (7), 1245-1262, 2005.
Abstract   PDF  
Ledwell, J. R., T. F. Duda, M. A. Sundermeyer, and H.E. Seim, Mixing in a Coastal Environment, Part I: A View from Dye Dispersion. J. Geophys. Res., 109 C10013, doi:10.1029/2003JC002194, 2004.
Abstract   PDF  
Sundermeyer, M. A., J. R. Ledwell, Lateral Dispersion over the Continental Shelf: Analysis of Dye-Release Experiments, J. Geophys. Res., 106 (C5), 9,603-9,621, 2001.
Abstract   PDF  
 

Prof. Miles A. Sundermeyer
The School for Marine Science and Technology
706 South Rodney French Blvd., New Bedford, MA 02744-1221
voice: 508.999.8892 fax: 508-910-6371 e-mail: msundermeyer@umassd.edu
www.smast.umassd.edu/msundermeyer