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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BP GRI Phase I

Click here for a PDF of the abstract

 

A new manuscript related to our BP-funded Rapid Gulf Research Initiative research has been published in the journal Continental Shelf Research.  A full citation is provided below. The published article can be found at the journal  web site located {here}.

 

  • Dzwonkowski, B., Park, K., Lee, J., Webb, B. M., Valle-Levinson, A. 2014. Spatial variability of flow over a river-influenced inner shelf in coastal Alabama during spring. Continental Shelf Research 74, 25-34.

 

 

Click here for a PDF of the abstract

 

A manuscript that I co-authored with my former post-doctoral student, Dr. Jungwoo Lee, has received final acceptance for publication in the journal Continental Shelf Research. Click on the cover art at right for a PDF of the manuscript abstract. A temporary citation is provided below. The publisher has made this article immediately available through its web site located {here}. Note that the rapid access version has not received final copy-editing or formatting.

 

  • Lee, J., Webb, B. M., Dzwonkowski, B., Park, K., Valle-Levinson, A. 2013. Bathymetric influences on tidal currents at the entrance to a highly stratified, shallow estuary. Continental Shelf Research 58, 1 – 11. doi:10.1016/j.csr.2013.03.002.

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.

 

 

 

As part of our 2011 GoMRI Rapid Response research on flow structures and transport across the Alabama shelf, we (University of South Alabama, Dauphin Island Sea Lab, University of Florida) teamed up with Dr. Joe Calantoni of the Naval Research Laboratory (NRL) – Stennis Space Center for a collaborative field experiment in October 2011. The NRL loaned us their Quadraped, a large pyramid-shaped stainless steel frame (seen in photo at right) outfitted with 1) an upward-looking Nortek Acoustic Wave And Current (AWAC) sensor, 2) four downward-looking Nortek Aquadopp Pulse Coherent Acoustic Doppler Profilers (PCADP), 3) two sector scan sonars, and 4) two pencil beam sonars… in exchange for a ride to the deployment site and some babysitting.

 

The Quadraped was deployed in about 17 meters of water south of Dauphin Island, Alabama from October 25 – 28, 2011. The instrumentation worked flawlessly, yielding near-complete vertical profiles of shelf currents, as well as surface wave statistics and bed morphology, for almost three full days. The final data inventory will provide an opportunity to extract the subtidal shelf currents from two complete diurnal tidal cycles. Additional data collection during the field deployment included obtaining hourly profiles of hydrography (e.g., temperature, salinity, density, etc.), in situ sampling of total suspended solids (TSS) using a rather novel technique, and continuous vertical profiling of hydrography every three hours (over a ten-minute period) to detect the presence of internal waves.

 

With this unique inventory of data we hope to develop a more complete description of subtidal forcing on the Alabama shelf, as well as estimates of bed stress, bed friction, and TSS behavior. A detailed description of the deployment, instrumentation, and data is forthcoming in a manuscript. Check back often for updates on QUADEX 2011. Thanks to the following partners and collaborators for their expertise and assistance:

  • The Naval Research Laboratory – Stennis Space Center: Dr. Joe Calantoni, Ed Braithwaite, Conrad Kennedy
  • University of South Alabama: Chris Marr, Richard Alan, Dr. Jungwoo Lee
  • Dauphin Island Sea Lab: Dr. Kyeong Park, Dr. Brian Dzwonkowski, Howard, Mimi, Kyle Weis, and Mike Dardeau
  • University of Florida: Dr. Arnoldo Valle Levinson

 

 

 

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…