Sediment swirling in the Gulf of Alaska

Today’s Image of the Day from NASA Earth Observatory features sediment swirling in the Gulf of Alaska on December 29, 2023.

“After an unusually snowy start to winter, southern Alaska’s coastline remained under a blanket of white in late December,” said NASA.

“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.”

According to NASA, 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,” explained NASA.

Aimee Neeley, a biological oceanographer at NASA’s Goddard Space Flight Center, noted that there are always phytoplankton in the water, but usually at lower levels in the wintertime at these latitudes.

The Gulf of Alaska is a vast and biologically rich body of water that lies at the northernmost part of the Pacific Ocean, encircled by Alaska. 

The gulf extends approximately 1,500 miles from the Alaska Peninsula and the Aleutian Islands in the west to the Alexander Archipelago in the east.

Characterized by a subarctic climate, it’s known for heavy rain and snowfall. The region is also prone to frequent storms and is a significant pathway for colder northern weather patterns moving into the United States.

The Gulf of Alaska is home to a diverse marine ecosystem. It supports many species of fish, such as salmon and halibut, and is also a habitat for marine mammals like whales, sea lions, and seals.

The image was captured by the MODIS (Moderate Resolution Imaging Spectroradiometer) instrument on NASA’s Aqua satellite.

Image Credit: NASA Earth Observatory 

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