Waters off the British Isles sprang to life with colorful swirls in early April 2025. The phenomenon commonly occurs in these North Atlantic waters in spring, but the view from orbit demands the cooperation of clouds.
Clouds stayed well offshore across the archipelago on April 7, 2025. That afternoon, the VIIRS (Visible Infrared Imaging Radiometer Suite) on the Suomi NPP satellite passed over the region and captured this striking image of the waters around the United Kingdom and Ireland.
Some of the colorful swirls, especially those close to shore, are likely due to sediment and other materials suspended in the water. Sediments are carried to sea by large rivers such as the Severn and get churned up from the seafloor by strong currents and waves. Satellite-based research has shown that in the Irish Sea, these mineral particles can exhibit complex spatial and seasonal patterns.
By spring, though, it’s likely that some of the colorful appearance across the region’s waters is due to phytoplankton—tiny plant-like organisms floating in the ocean. Under the right conditions, their populations explode into “blooms” that can span thousands of square kilometers of the ocean’s surface, making them visible from space. In this scene, the bloom in the North Sea appears to stretch several hundred kilometers offshore. The milkier, lighter-colored waters usually indicate the presence of coccolithophores, while greener areas often consist of diatoms.
Like elsewhere in the world’s oceans, phytoplankton around the British Isles feed the copepods and other plankton and fish that become food for even larger marine animals. However, a 2023 study of phytoplankton in the northeastern Atlantic Ocean showed that many of the region’s phytoplankton communities are changing—increasing in the North Sea but generally decreasing farther offshore—with possible implications for the food web.
NASA Earth Observatory image by Wanmei Liang, using VIIRS data from NASA EOSDIS LANCE, GIBS/Worldview, and the Suomi National Polar-orbiting Partnership. Story by Kathryn Hansen.
