Sea Technology

AUG 2012

The industry's recognized authority for design, engineering and application of equipment and services in the global ocean community

Issue link: http://sea-technology.epubxp.com/i/77248

Contents of this Issue

Navigation

Page 46 of 79

Surveys conducted across Main Pass and Pass aux Herons, The Jag Ski is outfitted with a suite of water velocity and water quality sampling equipment. the two estuarine connections of Mobile Bay to the Gulf of Mexico, provided an insight into the near-simultaneous distri- bution of tidally driven flows between the two inlets, as well as distributions of near-surface water chemistry. Of particular interest were the time-dependent relationship between the two inlets in terms of discharge magnitude and direction, and the existence of exchange between them through the lower por- tion of the bay. An analysis of ADP data from the two inlets has made it pos- The dynamics of river discharge and tides from the Gulf of Mexico result in a wide range of salinity in Mobile Bay. Salin- ity, measured in practical salinity units from 0 for pure fresh- water to 42 for highly saline ocean water, is often as low as 5 practical salinity units, but, in drought conditions, the salt wedge pushes well north of the bay into the delta and rivers, raising salinity. During the same survey, it would not be un- common to have salinities ranging from 5 to 30 practical salin- ity units, which is near oceanic salinity. Accounting for salinity and temperature in coastal surveys is important because those variables affect the speed of sound and, therefore, ADP data. The Jag Ski is also equipped with a SonTek CastAway CTD. At every kilometer or so, the instrument is cast to steadily free- fall with a sampling rate of five samples per second. Data from the CastAway integrates with the ADP's RiverSurveyor Live soft- ware package, generating sound-speed corrections for the acoustic data. The software yields real-time water velocity, di- rection and estimates of discharge, and allows information to be viewed in multiple data sets simultaneously during surveys on the waterproof computer aboard the Jag Ski or back on shore. The program integrates GPS, CTD and ADP data, and exports to MathWorks Inc.'s MATLAB or Hypack Inc.'s (Mid- dletown, Connecticut) HYPACK software. Monitoring Hydrocarbons, Water Quality To monitor the Deepwater Horizon spill's environmental im- pact on Mobile Bay, a YSI Integrated Systems and Services (St. Petersburg, Florida) Portable SeaKeeper 1500 was added to the Jag Ski. The SeaKeeper contains a YSI 6600 V2 multiparameter sonde, equipped with probes to measure temperature, con- ductivity, pH, turbidity, dissolved oxygen (DO) and chloro- phyll. It also has a C3 submersible fluorometer from Turner Designs Inc. (Sunnyvale, California) that measures chro- mophoric dissolved organic matter, crude oil and refined fuels. With a diaphragm pump and manifold system that keeps a steady flow of water over the instruments from 10 centimeters below the surface and an inlet designed to track with the PWC as it turns, the Portable SeaKeeper can sample accurately up to 40 knots, reporting data at five samples per minute. A number of surveys were conducted in the lower portion of Mobile Bay, and on local rivers connected to the bay, in early 2011 to map the spatial distribution of buoyant sus- pended hydrocarbons near the surface. These surveys generally also included underway measurements of currents using the ADP, and vertical profiles of temperature and salinity using the CTD profiler. sible to diagram the ebb and flood tide transport pathways be- tween the Gulf of Mexico, Mississippi Sound and Mobile Bay. Additionally, the data have documented a persistent recircu- lation developing on the east side of Main Pass, near the Fort Morgan peninsula, likely produced by vorticity generated through strong lateral shear in the along-channel flows found in the inlet. However, the presence of hydrocarbons was minimal; meas- ured values of crude oil and refined fuels were not significantly above background levels measured near public boat launches and inside local marinas. This was not surprising, as the oil well had been capped eight to nine months earlier, and the above- average freshwater input from the Mobile and Tensaw rivers to the bay produced a strongly ebb-dominated system and in- creased the flushing capacity of the lower bay during that time. Studying a Barrier Island The Jag Ski was also deployed in June 2010 to study BP plc's (London, England) effort to close off a breach in Dauphin Is- WHAT WERE YOU DOING 25 YEARS AGO? In 1985 Tecnadyne GHOLYHUHG LWV ¿UVW WKUXVWHUV VL[ 0RGHO ¶V IRU WKH 579 ¶V EXLOW E\ 0LWVXL RI -DSDQ 6LQFH WKHQ WKUXVWHUV LQFOXGLQJ 0RGHO KDV RYHU ZH KDYH GHOLYHUHG RYHU ¶V $QG HYHQ WKRXJK RXU FXUUHQW 0RGHO GHVLJQ LPSURYHPHQWV IRU UHOLDELOLW\ HI¿FLHQF\ DQG PDLQWDLQDELO LW\ ± WRGD\¶V 0RGHO LV VWLOO DJR 6R HYHQ DIWHU VWLOO SXUFKDVH RU UHSDLU D 0RGHO FRPSDWLEOH ZLWK WKH 0RGHO 529¶V ZRUNLQJ $QG LQ WKRVH \HDUV 0RGHO EHLQJ ¿WWHG WR QHZ 529¶V DQG $89¶V ZRUOGZLGH /LNH WKH 0RGHO WKDW ZDV LQVWDOOHG RQ WKDW ¿UVW 579 V\VWHP \HDUV \HDUV 0LWVXL RU DQ\ FXVWRPHU FDQ WKUXVWHU WR NHHS LWV ÀHHW RI SRZHUHG YHKLFOHV KDYH VXFFHVVIXOO\ FRPSOHWHG WKRXVDQGV RI URXWLQH PLV VLRQV DQG VHYHUDO DPD]LQJ RQHV $QG 0RGHO ¶V DUH VWLOO Tecnadyne's RWKHU WKUXVWHU PRGHOV KDYH VHUYHG WKH RIIVKRUH FRPPXQLW\ ZLWK UHOLDELOLW\ KLJK SHU IRUPDQFH DQG FRVW HIIHFWLYHQHVV Tecnadyne LV FRQVWDQWO\ GH YHORSLQJ QHZ WKUXVWHU PRGHOV ZLWK LQWURGXFHG LQ WKH ODVW \HDUV DORQH It is Tecnadyne's FRPPLWPHQW WR LWV FXVWRPHUV DQG WR WKH VXE VHD FRPPXQLW\ WKDW QR 529 $89 RU PDQQHG VXEPHUVLEOH ZLOO HYHU EH PDGH REVROHWH EHFDXVH WKH Tecnadyne WKUXVWHUV LQ VWDOOHG RQ WKDW V\VWHP DUH QR ORQJHU DYDLODEOH IRU D UHDVRQDEOH DQG FRPSHWLWLYH SULFH 6R IRU \RXU QH[W 529 $89 RU PDQQHG VXEPHUVLEOH EXLOG RU SXUFKDVH EH VXUH WR VSHFLI\ RQO\ JHQXLQH Tecnadyne WKUXVW HUV

Articles in this issue

Links on this page

Archives of this issue

view archives of Sea Technology - AUG 2012
loading...
Sea Technology
Welcome!
If you're not a subscriber, please click here.