The dye release yesterday (May 8th) was very interesting. The dye release was initiated shortly after slack tide as the water started ebbing. 30 gallons of Rhodamine WT were released in 2:24 min. As usual the mounted instruments, the jetskis, NPS/RSMAS crew, REMUS, towed ET array, and the Partenavia were all measuring the dye plume. At first, as the tide was still not very low, the dye poured down the main channel and then oozed out over the southern shoal. See the aerial hyperspectral image below (taken at 1339 local time, from Luc Lenain and Nick Statom). Up the inlet near where the dye was released, the surface dye is very patchy because the dye is released about 3 m above the bed in ~9 m water depth. At times it seems like the surface dye patch has a periodic signature. The dye moves offshore of the south-western shoal in jets and squirts.
The nice thing about this image below is that it can be used to quantify Rhodamine dye concentration. As light is measured across a spectrum of wavelengths, information at absorption and emmision wavelengths of dye will be used to calibrate dye concentration against in situ sensors.
Below are some SLR camera images of the plume at similar stages. These are useful for providing context but are nowhere near as quantitative.
The imagery above is a preliminary mosaic of the New River inlet plume on May 2, at about 1150 EDT (the companion data to Gordon Farquaharson’s microASAR data in his May 4 post). Brightness in the image indicates relatively warmer temperatures, and I’ve adjusted the contrast to highlight the plume, making the warmer land white. The plume on this day (due to wind) was shooting north and the plume front(s!) are complicated – including prominent transverse features at N = 3822.5km, E = 286 to 288km. Note there are still kinks in the mapping, so image overlap is not exact, and the camera drift and angular emissivity effects have not been corrected.
First ever blog post for me. The ‘other’ Scripps group has been running the REMUS AUV to characterize inlet dynamics and map the outgoing plume. Before the dye surveys, we ran a series of missions to survey the naturally occuring optical signals leaving the inlet over an outgoing tide. Above are cross-sections of CDOM across 4 different transects. We’ve also run some offshore to onshore transects to characterize how far offshore the plume is advecting and characterize the vertical structure. Should be interesting to compare with the remote sensing imagery. -Eric