Contact

Bret M. Webb, Ph.D., P.E., D.CE
Professor
University of South Alabama
150 Jaguar Drive, SH3142
Mobile, AL 36688 USA
Phone: (251) 460-6174
Fax: (251) 461-1400
Email: bwebb@southalabama.edu

Research Positions

None available at this time

Current Research Assistants

SE Students
Garland Pennison

 

MSCE Students
Patrick Hautau
Marshall Hayden
Kate Haynes
Justin Lowlavar
Vijaya Satya Lohitha Mukkamala
Jackie Wittmann

 

Undergraduate Students
Derek Kelly
Rh'Monte Wilson

Former Students

MSCE Students
Bryan Groza (2016)
Kari Servold (2015)
Chris Marr (2013)
Richard Allen (2013)
Miyuki Matthews (2012)

 

Post Docs
Jon Risinger
Jungwoo Lee

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drifters

One of our drifters (DISL023) released at the 20-meter isobath on April 26, 2012 woke up after an extended nap and started reporting again on October 16, 2012. In the days that followed, the drifter made it into the Loop Current, scooting quickly across the southern portion of the Gulf of Mexico headed toward Fort Jefferson in the Dry Tortugas at speeds approaching 2 knots. The drifter has now merged with the Florida Current. Click on the image at right for the interactive tracking page. Also, you’ll see a small embedded tracker as the second item in the left hand column of this page.

 

The figure below shows a comparison of the drifter trajectory and mean ocean surface currents for the period 10/15 – 10/25. The data were obtained from the NOAA OSCAR system, which provides satellite derived estimates of ocean surface currents*. The inset panel shows more detail around the drifter trajectory, along with drifter speeds (m/s) and position dates (10/16, 10/26). Note the excellent agreement between drifter speed and ocean current magnitude (using the color scale at right). Clicking on the image below will take you to an enlarged version for easier viewing.

 

OSCAR mean surface currents for the period Oct 15 – 25, 2012 overlaid with the trajectory of DISL023.

 

 

*Bonjean F. and G.S.E. Lagerloef, 2002: Diagnostic Model and Analysis of the Surface Currents in the Tropical Pacific Ocean, Journal of Physical Oceanography, Vol. 32, No. 10, pages 2938-2954.

 

 

 

Our fourth and final drifter deployment took place yesterday in the Gulf of Mexico south of Dauphin Island, Alabama. Drifter deployments started in July 2011 as part of a year-long group of coordinated research projects focused on identifying the physical transport mechanisms of buoyant suspended matter in Alabama’s coastal waters. More information about the drifter deployments can be found {here}.

 

As it so happens, Alabama’s inner shelf is dominated by two seasons… kind of like Mobile, which has two seasons: hot and hotter. Drifter deployments in July and August 2011, both west of Mobile Bay and in depths of 20 meters or less, described an eastward surface current thought to be associated with predominant southerly winds and downwelling favorable conditions. All drifters deployed in late October, however, moved to the west and south. A likely cause of this dramatic change of inner shelf conditions is the dominance of northerly winds in late fall, the resulting Ekman divergence, and the facilitation of upwelling favorable conditions on the shelf. The batch of drifters deployed yesterday are again moving eastward similar to those deployed in July and August 2011.

 

We started yesterday’s deployment (Figure 1) by placing nine drifters near the ship channel at Main Pass, the primary connection between the gulf and Mobile Bay (Figure 2). Six of the drifters were deployed on the east side of the channel while the remaining three were set adrift to the west of the channel. From there, we made our way offshore and released nine drifters at the 30-meter isobath. We then deployed our final seven drifters near the DISL FOCAL station in a little less than 20 meters of water. Winds were strong and out of the SSW for much of the day, which made for a lumpy day on the water.

 

Figure 1. A general location overview of the April 26, 2012 drifter deployment. Each circle represents a cluster of 7 – 9 drifters that were set adrift.

Figure 2. A more detailed view of the drifter deployment at Main Pass shows the location of each drifter “triad” that was released near the ship channel. Each triad contains three drifters and the triads form the vertices of a larger triangle having sides of approximately 1000 meters.

 

More information regarding yesterday’s deployment will be made available in the coming weeks as a dedicated page under the “Drifters” tab above. There, you will be able to see details about the drifter deployment patterns and links to tracking pages. For now, you’ll have to settle for the following tracking interfaces…

 

 

 

A heartfelt thank you goes out to Captain Hayden Abel of Texas, formerly of the University of Texas Marine Science Institute, who was kind enough to let us know that he had found one of our drifters washed ashore near Port Aransas, Texas. Capt. Abel, as it turns out, had to do quite a bit of investigative work to track us down by email. I guess numbers stenciled with spray paint are no match for the sea, sun, and sand that this drifter encountered during its journey. Although I cannot be sure which drifter was found, I do know that it was part of the October 2011 release (it is likely to be DISL 019).

 

I can only assume this drifter was trying to make it to South Padre Island in time for Spring Break… so close little buddy… so close.

A number of CE graduate students and faculty are presenting their research at the annual USA Spring Research Forum the week of March 26 – 30, 2012. Research posters are displayed in the lower and upper lobby of the Mitchell College of Business (MCOB). A formal research symposium will be held on Friday, 3/30. The CE posters are on the lower lobby level on boards 17 – 20. Students are encouraged to view the posters to gain an appreciation for the research that USA students, both undergraduate and graduate, and faculty are performing. Some reduced-scale versions of the posters can be found below the corresponding citations that follow. Please contact me if you’d like more information about these or other projects.

 

  • Allen, R.J., B.M. Webb 2012. Wave Attenuation Devices: a Comprehensive Evaluation of Wave Transmission through Physical Modeling. University of South Alabama Spring Research Forum, Poster 20. March 26 – 30, 2012. Mobile, AL.

 

  • Marr, C.D., B.M. Webb 2012. Spatial Variability of Residence Time in Mobile Bay, Alabama. University of South Alabama Spring Research Forum, Poster 19. March 26 – 30, 2012. Mobile, AL.

 

  • Miyuki, M.T., B.M. Webb 2012. Characterizing Wave-Induced Scour Processes in a Transition Zone: a Continuum Model for Equilibrium Scour Depth at Cylindrical Piles. University of South Alabama Spring Research Forum, Poster 18. March 26 – 30, 2012. Mobile, AL.

 

  • Webb, B.M., S.H. Russ, D.B. Martin. 2012. Development of an Enhanced Ocean Drifter. University of South Alabama Spring Research Forum, Poster 17. March 26 – 30, 2012. Mobile, AL.

 

This is a very brief update on the status of all drifter trajectories to date. There are currently seven active drifters remaining from the October 27, 2011 deployment. Three of the seven are now west of the Mississippi River delta, and the other four are east of the delta. A couple of weeks ago, one of the drifters from the 30-m cluster merged with drifters from the 20-m cluster when they crossed paths north and east of Middle Ground. The image at right shows the trajectories of all drifters released to date. Click on the image to enlarge.