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Oceanography I
Professor Graus
Due: 30 April 2002

by OCEAN 6: Vonne (Shavonne L. Marshall  ), Tina  , Paul, Erik (Erik Fossum), Drew (Charles Rawls), Dianne (Dianne Mollica), Cassi (was sick)

Wallops Island Field Trip Report: Part 2


Seaweed carried in net

Results and Discussion

V.Currents, Tides, and Other Wave Actions

        We examined two sites during our trip to Chincoteague.  There were many differences that were observed in the tidal currents, as well as regular currents, between the two sites.  Many factors tie into the differences that were apparent and some differences can be explained by oceanographic inquiry.  A thorough examination of these similarities and differences will be examined in the following report.
        Lets begin with the tides.( www.harbortides.com)  Both sites provided rather predictable readings of the tide levels for the date the field trip was taken on.  Statistical information taken from both Wachapreague and Wallops Island stations would lead one to predict tides that have just begun rising from their lowest cyclic averages.  The tide was low at the first location, and lower at the second location.

        Typically, the area has its lowest tide during a neap tide, when the moon is new, and occurs around 3 AM in the morning and afternoon.  Readings taken from NOAA and HarborTides.com displayed tide levels that were going out (the water-level is lowering) at the times when the boat was stopped for measurements.  At the first location, according to the predictions, the tide should have been higher than the time of the second stop.  Data is consistent with these predictions.  The tide at Wachapreague was just 0.003-0.002 MLLW (mean lower low water) at approximately 1:30 EST (eastern standard time) and was 0.001 MLLW at approximately 3:30 EST.  This suggests that the tide was going towards low tide, which is precisely what was supposed to be taking place.  The tide readings from Wallops Island state that low-tide on April 14th occurred at 3:24 EST and was approximately 0.06 meters MLLW, almost the exact time the boat was stationed at its second stop.  It was clearly evident that there was a very low tide when returning to the shore because the boat was literally dragging the bottom in the channel.  This all ties into the fact that there had just been a neap tide, in which the tides are usually lower than normal.  It makes sense that two days after a new moon the tidal forces are still expected to be lower than usual.
        Secondly the regular ocean currents are examined. (Co-ops.nos.noaa.gov/) It was clearly evident that the waves were much more turbulent at Chico Inlet, the offshore location.  The water depth was greater (approximately 8.4 meters in depth), and the location was more out in the open sea.  The in-shore location, Cockle Creek, (www.mapserver.com) had significantly calmer waves and less turbulence.  This is most likely because the depth was only 5.5 meters, and the boat was not out in the open sea where waves are typically higher and free to build.  Cockle Creek had many sand bars and a lower depth. The lower depth allows the waves to hit objects, such as the shore and the bottom, and spread them out.  In the open ocean, the waves do not touch bottom and build in wave height, not wave length.  Some similarities probably exist in the areas of currents.  Since there was not a major significance in depth, there was probably no major difference in deep water currents.  The boat’s locations never entered the continental slope so that eliminates the possibility of turbidity current affects.  There also was probably not much upwelling, or down welling, because that occurs where there is a greater difference in water temperature at different depths.  The water temperature was fairly consistent and did not differ immensely from surface to deepwater measurements.
        To summarize, the tides were fairly consistent with predictions and expectations of tide levels for the given date.  They also were the same throughout in structure or composition at the times the boat stopped to take measurements, and also with the tidal cycle.  Information on surface currents could not be obtained, but there were some clear similarities and differences between the wave actions at both locations.
 

<for Part 1 of our Trip Report Click Here>



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