Swirls of green and blue colored the deep blue waters of the South Pacific Ocean off the east coast of New Zealand as the surface waters reflected the shimmer of sunglint in mid-November 2021. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite acquired this true-color image on November 19.
The jewel-toned colors riding the ocean currents are caused by a bloom of phytoplankton, which are microscopic plant-like organisms. They live in the waters year-round in small numbers but when conditions are favorable, they begin to reproduce explosively, creating giant “blooms” that are easily seen from space. The waters east of New Zealand often provide a rich environment for phytoplankton growth. This is where currents from the Indian Ocean and the Pacific Ocean meet. As they pass by each other, the turbulence stirs up cool, nutrient-rich waters from the ocean depths. Springtime brings sufficient sunlight, helping spur the growth of the surface-dwelling phytoplankton.
While the brilliant ocean color comes from living organisms, silver-toned sunglint is an optical phenomenon. This occurs when sunlight reflects off the surface of water at the same angle that a satellite sensor views it. The result is a mirror-like specular reflection of sunlight off the water and back at the satellite sensor or astronaut.