Something (or Nothing) in the Water:
Seeing the Differences in Warm and Cool Water
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The image above is a "real" (visible-light) image of the Gulf Stream. Notice that the warm-core rings are visible even in this real image as portions of water with color different from the surrounding water. The cooler of the two warm rings is colored a light green, while the warmer of the two is a deep blue color similar to the color of the Gulf Stream water itself (just visible at the northwest corner of the cloud bank). The color of the water is a good indication of what it contains, and gives us a clue as to why we would expect bird and cetacean species found in the tropical water to be different than those found elsewhere. The water found over the relatively shallow continental shelf contains high concentrations of phytoplankton (floating plants and animals). This phytoplankton contains clorophyll that absorbs highly in the blue portions of the visible spectrum, but reflects green light. The high concentrations of these plankton also scatter light entering or leaving the water, making it difficult to see objects much below the surface of this green water. The image below was taken with the Coastal Zone Color Scanner instrument carried on the NIMBUS-7 satellite, an instrument that measured reflected wavelengths of light very precisely. The colors in the image below show the relative concentrations of these phytoplankton. Just as in the picture above, the warm-core ring stands out as an area with low concentrations of phytoplankton. |
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(Image from NASA Classic CZCS Scenes) |
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Hot Enough for Ya? |
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The Trip Temperature Outlook
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| The conditions for our search for warm water looked fairly good. Although there didn't seem to be any specific warm rings around the canyons, the water near the canyons was definitely warm. More importantly, the water temperature changed rapidly over a small distance in several places. These temperature boundaries can be very hospitable for concentrations of sea life. |
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Above: A sea-surface temperature plot for the day before our trip left shore. Note the sudden temperature shifts near the middle of the plot, just east of Hydrographer's Canyon. |
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An Advanced Very High Resolution Radiography (AVHRR) satellite image showing temperatures for the Gulf of Maine over the seven days prior to the CORE trip departure. The image is a composite of seven days of data; some small, fluctuating features will be washed out by the creation of such an image. (Click on the image for a larger version.) |
| Of course, the geographic boundaries of the canyons themselves were the real reason we were visiting this area. The steep walls of the canyons are what give them their special place as harbors for marine life. |
| Back: Gulf Stream Eddies |
