As rivers wash sediment toward the sea, they carve elaborate deltas like that of the Rio Cauto in Cuba. Over time these sediments build up marshes, swamps, lagoons, and other wetlands that provide critical habitat and flood control. Sediment also washes into the bay, where it interacts with the coral reefs (light green lines on the lower left) and the species that live there. (Image credit: L. Dauphin/USGS; via NASA Earth Observatory)
This false-color satellite image — the recent winner of NASA Earth Observatory’s Tournament Earth 2020 — shows sands and seaweed off the coast of the Bahamas. Ocean currents and tides eroded these elaborate fluted designs in much the same way that winds sculpt desert dunes. The overlap in form is no accident; as seen in recent work, researchers are finding that both air and water move granular materials like sand according to the same rules. (Image credit: S. Andrefouet; via NASA Earth Observatory)
Rafts of sea ice follow swirling eddies in this satellite image of the Gulf of St. Lawrence. Just as with phytoplankton blooms and sediment, this thin sea ice can be moved by wind and currents to reveal hidden flow patterns. Experimentalists use many similar diagnostics that introduce bubbles, particles, smoke, and other tracers into flows to visualize motion that’s otherwise invisible. (Image credit: J. Stevens/NOAA/NASA; via NASA Earth Observatory)
Crisscrossing lines of wave clouds mark the wake of the Sandwich Islands in this satellite image. The tallest islands in the chain thrust rocky peaks more than 1000 meters above sea level, disrupting winds flowing across the ocean. Incoming air is forced up and over the mountain, which puts it at odds with the surrounding air at that height.
Due to differences in temperature and density, the disrupted air will continue to rise and sink periodically as it flows onward. At some heights it will cool enough to condense its water vapor into clouds, and at others, it will warm enough to lose any cloud cover. This is what creates the bands of clouds we see behind each individual island. (Image credit: L. Dauphin/NASA; via NASA Earth Observatory)
Blackwater rivers, like the Suwannee River in Florida, carry waters so laden with organic material that they’re dyed a deep, dark brown. For the Suwannee, most of this material comes from the rich peat deposits of the Okefenokee Swamp that lies upstream. As vegetation in the swamp decays, tannins from the plants dissolve into the water, giving it its distinctive color, which the river maintains along its full 400-kilometer journey to the Gulf of Mexico. The dark waters of the river act as a tracer, revealing how the fresh river water mixes with the ocean in the enhanced-color satellite image above. It’s amazing to see how far the river’s influence spreads before delicate wisps of color pierce the darkness. (Image credit: U.S. Geological Survey; via NASA Earth Observatory)
Sunglint on the ocean surface can sometimes reveal different patterns in wave conditions. In the satellite photo above, we see the Canary Islands with wavering silvery wakes stretching to the southwest. The predominant wind direction over the islands is from the northeast. The rocky islands act as a wind-break, redirecting the flow and shadowing the ocean in their wake from much of it. As a result, fewer waves are stirred up in the islands’ wakes, thereby changing the local surface reflection properties and making this image possible. (Photo credit: NASA Earth Observatory)
Swirls of blue in the Great Lakes mark locations of recent autumn storms whose winds have stirred up sediment in the lakes. The silt and quartz sand acts as a tracer particle, making visible the circulation patterns of the lakes. In contrast, the green streaks mark locations of calmer winds and warmer temperatures where algae blooms have grown. Note the fundamental dissimilarity in their structures. Blue eddies turn over and mix in a fashion reminiscent of convective instabilities while the green blooms are far more uniform in structure. #
The von Karman vortex street isn’t just found in the wake of cylinders in a lab. Wind moving over islands frequently creates the effect, as in this MODIS Aqua image of the coast of Baja California, Mexico. #