In mid-March 2022, skies were clear over the eastern end of the English Channel (The English Channel), even if the waters were not. Spring in these northern seas is often accompanied by the flow of sediment from rivers, the churning of seafloor sediments, and the blooming of floating, plant-like phytoplankton that thrive on the influx of nutrients and water. ‘pure water.
“The optical complexity of the eastern English Channel and southern North Sea waters is a veritable witch-mix of suspended sediments from the Thames Estuary and the soft substrates of the French and Belgian coasts,” said Tim Smyth, chief scientist of marine biogeochemistry. and observations at the Plymouth Marine Laboratory (UK). These sediments are usually stirred up by strong waves and currents that move back and forth across the English Channel. “The complexity of the currents and the ever-changing bathymetry of the seabed shape the beautiful filamentary patterns of this region.”
Smyth also suggested that some patches of the North Sea and English Channel could be discolored by spring phytoplankton blooms. “The optical complexity of the meeting of the English Channel and the North Sea makes it difficult to separate the sediments from the chlorophyll signal there,” he added.
The natural color image above was acquired on March 17, 2022 by the HawkEye multispectral sensor aboard the SeaHawk CubeSat. Besides the sediment, note the many bright little specks in the water, mostly ships and boats passing through one of the busiest shipping lanes in the world. Also note the bank of stratocumulus clouds (lower right) and the shadow they cast over northern France.
“It’s extremely rare to have a cloudless day in this region,” said Alan Holmes, the Cloudland Instruments engineer who built HawkEye. “That doesn’t happen often in wide fields of view.”
SeaHawk is a relatively new nanosatellite designed to monitor ocean color and coastal ecosystems. The tiny satellite is about the size of a shoebox and flies in a polar orbit at 585 kilometers (363 miles) above sea level. SeaHawk was funded by private grants and built by a team led by the University of North Carolina, Wilmington. NASA scientists assisted in the development and have since worked to integrate the data with other ocean color datasets.
Older ocean-viewing satellite instruments, such as the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), had lower spatial resolution and large data pixels that made it difficult to research coastal environments in detail. SeaHawk was designed to fill this void by providing data with eight times the spatial resolution of SeaWiFS. This small satellite was designed, in part, to prove that certain measurements of ocean color in coastal ecosystems could be made more often and more cheaply.
NASA image by Alan Holmes/NASA Ocean Color Web, using data from SeaHawk/HawkEye. Story by Michael Carlowicz, with contributions from Gene Feldman, NASA.