Dye Tracer Experiment

Dye Tracer Experiment Figures

Figure 1: Cross-shelf (along a PRIMER transect 30° from the cross-shelf axis) temperature section across the shelfbreak front south of Martha's Vineyard two weeks before the pilot cruise, courtesy of Bob Pickart.
Figure 2: Cruise track during the injection and detection of the dye patch. Three surveys are identified as TR3, TR4, and TR5. Bottom bathymetry is indicated. Contours of dye concentration in units of 10^-11 are 5, 12, and 40 for TR3 and 2.5 and 5 for TR5. Note the rapid onshore displacement of the dye patch and hence the frontal boundary from the 100m to 80m isobath between TR3 and TR4.
Figure 3a: Representative cross-shelf section of dye concentration across the dye patch during the three surveys showing BBL dye concentration as a function of temperature.
Figure 3b: Representative cross-shelf section of dye concentration across the dye patch during the three surveys showing BBL dye concentration as a function of distance.
Figure 4: A schematic diagram of the evolution of the dye patch in the BBL at the foot of the shelfbreak front. The cross-shelf temperature profile is a mean derived from all sections taken during the cruise and is used to infer cross-shelf position relative to the front from temperature measurements. The position of the dye peak (dots) and approximate one standard deviation width of the patch for each survey are shown along with the time elapsed from the dye injection. The vertical gradient above the BBL at x=0 is from the dye injection measurements. Height of the BBL (dashed line) is defined by the height of the maximum vertical temperature gradient. Arrows qualitatively represent the flow although only the onshore flow is actually measured by the dye patch displacement. Isotherms are hand drawn to connect the mean BBL temperature with the vertical stratification at x=0 and to represent the cross-shelf variation in the vertical gradient. Between TR3 and TR4 the entire frontal boundary was displaced 12-15 km onshore.

Lamont-Doherty Earth Observatory of Columbia University