(June 04, 2015) --

Observation and Pictures by Dr. Brian Dzwonkowski

These pictures show a really nice example of a tidal intrusion front. High tide is around noon today (June 4, 2015) so the Bay is flooding. As a result, browner, saltier Mississippi Sound water is being transported into Mobile Bay under the Dauphin Island Bridge. In the bottom photo, you can see the classic 'V' structure of a tidal intrusion front as Mississippi Sound water pushes into Mobile Bay on the tail end of the flood tide. Mississippi Sound water is saltier than Mobile Bay water, so the front is pushing saltier water inwards. At the time of the photos, bottom salinity data at Katrina Cut is 19 PSU (Practical Salinity Unit), while Cedar Point is around 12 PSU.

Even more amazing is how well this behavior is captured in the Cedar Point data. One can see the sharp jump in salinity as the front passes by the My Mobile Bay Cedar Point station - the salinity nearly doubles over the course of an a couple hours as the front passes by. As can be seen from salinity data (i.e. really sharp jumps in salinity with the incoming tide) this behavior has been happening for the last several days! Really amazing! Based on the data from Cedar point, I would guess around 10:00-10:30 am will be a great time to see the front.

DISCLAIMER: Please do not stop/park on the Dauphin Island Bridge. Please always keep your eyes on the road. 😊