Sediment floating in the Gulf of Alaska lent contrasting color to this otherwise winter-white scene acquired by the MODIS (Moderate Resolution Imaging Spectroradiometer) instrument on NASA’s Aqua satellite on December 29, 2023.
Sediment floating in the Gulf of Alaska lent contrasting color to this otherwise winter-white scene acquired by the MODIS (Moderate Resolution Imaging Spectroradiometer) instrument on NASA’s Aqua satellite on December 29, 2023.
After an unusually snowy start to winter, southern Alaska’s coastline remained under a blanket of white in late December. Meanwhile, greens and tans swirled in the dark blue water offshore. The dullness of the hues near shore suggests that the water is mostly colored by sediment. It is likely that phytoplankton—microscopic plant-like organisms—contributed to some of the hues farther from the coast.
Much of the sediment in this region comes from “glacial flour” carried into the gulf by the Copper River. Glacial flour forms as glaciers move over bedrock and grind it into a fine silt. When suspended in water, glacial flour can make the water appear an opaque turquoise color—similar to phytoplankton blooms. The sediment carries iron and other nutrients that can spur the growth of these tiny marine organisms.
Read more at NASA Earth Observatory
Image: The burst of turquoise and tan hues in Alaskan waters is in stark contrast to the snowy shoreline. NASA Earth Observatory image by Michala Garrison, using MODIS data from NASA EOSDIS LANCE and GIBS/Worldview.
