Heavy winds blew across the Florida Bay in early January, 2012 stirring the waters and contributing to the dazzling array of color which stretched from the Gulf of Mexico to the Straits of Florida, and surrounded the Florida Keys. The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Aqua satellite captured this true-color image on January 4 at 18:30 UTC (1:30 p.m. Eastern Standard Time).
Clouds of milky blue, green and tan fill the waters in this region, especially where the water is shallow, such as in the Florida Bay and the easternmost Gulf of Mexico. Where the water deepens in the Straits of Florida south of the Keys and more westerly in the Gulf, the bright colors abruptly end, giving way to a deep ocean blue.
Bright colors in the ocean are most often caused by either sediment or by microscopic marine organisms, such as phytoplankton. In this location, the waters are very shallow. When the waters are rough, mud and sediment are easily churned up from the sea floor. It is likely that this particular colorful display comes primarily from sediments of various kinds floating in the off-shore waters.
Nearest the southern Florida coast, the waters are distinctly tan, which indicates run-off of particulates from land. As this sediment flows into deeper water and sinks, the reflectivity of the particles change, and the color changes from tan to green. Further south, near the islands known as the Florida Keys and the Dry Tortugas, coral reefs are abundant. The sediment in this area is rich in calcite, a building block of coral reefs. When disturbed, highly reflective calcite sediment can lend a milky appearance to the blue ocean water.