Eric Stone

Problems in Marine Science Research Project

Purpose:

To determine what has a greater influence on chlorophyll_a production along the N.J. coast in July 2001 nutrient runoff from land, upwelling or surface mixing. I will also be only looking for the days of the month that only had significant changes in chlorophyll_a.

Procedure:

To do this I will be comparing SeaWiFs satellite imagery of chlorophyll_a in mg/m^3 to rainfall along with wind direction from the Atlantic City weather observation tower, wave heights from the the Delaware Bay Buoy, and sea surface temperatures(SST) from a noaa satellite. The intensities of the upwelling will be estimated by using SST. If the SST decreases below two degrees Celsius then that upwelling would be considered weak to moderate. In estimating how much growth is caused by surface mixing I used daily wave heights from the Delaware Bay Buoy. The amount of nutrient runoff will estimated using daily rainfall data. To help distinguish what the increase in chlorophyll_a was caused from I used short wave radiation measured in Watts/m^2 at the Tuckerton NJ marine field station. Short wave radiation rages within 400-2500 nm in the color spectrum and is the main scource of light that enters our atmosphere therefore it can be used as an indication in a change in chlorophyll.

Satellite Lab Background :

The SeaWiFs satellite images were accessed using an XT user program on a command line interface.The SeaWiFs satellite measures light intensity by receiving color in eight channels.. The two main channels are three and four which are in the blue green regions of the color spectrum. The more channels that are used the better the data will be. . SeaWiFs satellites have smaller channels making the calculated chlorophyll concentration more accurate Coastal Zone Color Scanners. When CZCS were used in the 1980's they only had five channels. SeaWiFs imagery has a resolution of one km but only makes one pass over NJ a day. This experiment was done using images that have already been processed to generate chlorophyll-a in mg/m3. By using SeaWiFs satellite imagery I plan on finding out how much of an effect isolated factors have on chlorophyll_a concentrations. I predict that if there is a longer duration of rain, upwelling, or new production than one another then that factor will have the greatest effect on chlorophyll_a along the coast of NJ

Material and Methods:
To find out how the chlorophyll_a changes during July 2001 I picked two stations near shore and two stations offshore the coast of New Jersey. The stations locations are shown here in this map of New Jersey.

KEY NS(nearshore), OS(Offshore)

The same points were used to collect any data within +- .05 of a degrees latitude or longitude for the days of the month that had data. While recording chlorophyll_a concentrations at the stations I scaled a color bar from 0-10.Areas with low chlorophyll would appear as blue or green. Regions of high chlorophyll_a are yellow and red. The purpose for scaling all my chlorophyll images from 0-10 is to enhance any possible increases in chlorophyll_a along the coast by ignoring the very high chlorphyll_a concentrations in any rivers. A higher scale would allow for regions in a river to appears to have more variation according to color as opposed just showing up as dark red.. The scale for all my SST images was 8-38. Scaling my SST images is based on what season of the year it is, but in both cases scaling the image makes it possible to know how the water is changing because the data will always have the same color.

Results
The month of July 2001 had very varying weather patterns. Rainfall for July 2001 had very high rainfall early in the month followed by relativity no rainfall.

The average wave height was 1.103(m). Wave heights for the first half of the month were below average and mostly above average the rest of the month.

Key Delaware Bay Buoy (Delaware Bay Buoy)

The monthly wind direction was west south west.

Discussion and Conclusion :

Using the SeaWiFs satellite imagery days with large fluxes of chlorophyll_a occurred on July 6, 10, 13, 15, 21, and July 23, 2001. The largest increase in chlorophyll_a was on June 6, 2001. This was caused from changing environmental conditions from July 3 to July 6. There were increased wave heights from .5 to 1.3 meters. Short wave radiation increased during this time from 275 to 330 Watts/m^2. Rainfall increased 1.15 inches but upwelling stopped even though the winds were WSW. No upwelling may have occurred because wind speeds of 4.75 knots may have been too weak to break the thermocline. The dominate factors for the 6.34g/m^3 increase in Chlorophyll_a near shore and 8.27g/m^3 offshore where most likely from large increases in colored dissolved organic matter (CDOM) and nutrient runoff caused by 1.63 inches of rain from July 3rd through July 6th.

Time is in GMT military time.

SeaWiFs image of chlorophyll_a on July 6, 2001 1637

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Only four days later on June 10 there was almost no phytoplankton along the coast or offshore. This decrease was not caused by downwelling because the winds were out of the west. Taking a data point pretty close to the station because a cloud was in the way showed that the SST at NS station 2 was 2.28 C higher than what it was on June 6th. This was mostly likely caused from varying currents or just short wave radiation during June7th-June 10th increasing from 245 to 320 W/m^2. The main process that most probably caused a very large decrease is eutrofication. This happens when excess nutrients enter the water causing photosynthetic organisms to rapidly increase all at once resulting in the water column being striped of nutrients and soon after most photosynthetic organisms such as phytoplankton die because of this. Physical processes that could have aided eutrofication were greater surface mixing caused by higher wave heights on July 6th.

SeaWiFs image of chlorophyll_a on July 10, 2001. Time 1749

Increasing short wave radiation on June 13 may have caused phytoplankton to increase along the coast. At near shore station 1 chlorophyll_a increased by 2.35 mg/m^3 from June 10. During June 10th-12th short wave radiation increased from 300-325 W/m^2. There was no rain at this time and wave heights were .389 m below average. Winds were from the south and SST at station NS2 and OS2 showed slight variability and no upwelling. Decreasing short wave radiation may be responsible for 1.86 mg/m^3 lower chlorophyll_a near shore on June 15th. Rainfall and wave heights relativity stayed the same while short wave radiation decreased from 285 to 265 W/m^2 during June 13-June15. The average wind was from the north west and SST over the past three days did not indicate any downwelling. Therefore if there were no moderate increases in dissolved organic matter (DOM) being brought to the stations from the Hudson or Delaware River then these changes in chlorophyll_a were from changing short wave radiation.

SeaWiFs image of chlorophyll_a on July 13,2001. Time 1641

SeaWiFs image of chlorophyll_a on July 15, 2001 Time 1806

A combination of conditions that are a little above average such as rainfall, wave heights can lead to above average chlorophyll_a during periods of moderate short wave radiation. On July 21,2001 near shore chlorophyll was 2.8 mg/m^3 chlorophyll_a above average. Offshore chlorophyll_a was .76 mg/m^3 above average. Rainfall was only .18 inches above normal from three days prior while wave heights were 1.38 meters. Wave heights or rainfall however can't be separately contributed to a specific chlorophyll_a value because there are no days where there was an increase chlorophyll _a just from waves or rainfall.

SeaWiFs image of chlorophyll_a on July 21, 2001. Time 1726

Using meteorological data to account for changes in chlorophyll_a is not always predictable. This was the case on July 23, 2001. Chlorophyll_a increased by about 5mg/m^3 from July 21, 2001. The average wind direction from the June17-June 22 was south west, but SST showed temperatures increasing by about 1.5 degrees near shore and 2 degrees offshore. Increased chlorophyll_a still may have been caused by upwelling, but more data would by needed on how the currents were moving that day to understand why chlorophyll_a increased.

Overall the trend observed over the month showed chlorophyll_a was most limited by rainfall. Wave heights did not accounted for only a minor role. The monthly wind direction of west-southwest did not have as great of an effect as one might predict. Downwelling and very little rainfall for most of the month resulted in chlorophyll_a concentration being below average for most of the month. Short wave radiation changes of about 100W/m^2 over a two to three day 24 hour average seemed to cause chlorophyll_a to change by approximately 2 mg/m^3. SST days prior to a large change in chlorophyll_a did not always reflect upwelling or downwelling. Large changes in chlorophyll did not requre a long duration of a specific weather pattern such as rainfall as I previusly would have expected. In conclusion using SeaWiFs and SST satellite imagery along with meteorological data are effective tools for interpreting daily changes in chlorophyll_a. This is important because predicting more accurate patterns in chlorophyll will make better models of how productivity will change in the future.