Scientists discover unlikely culprit for fertilizing North Pacific Ocean: Asian dust

phys.org | 4/26/2019 | Staff
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The vast subtropical "gyres—large systems of rotating currents in the middle of the oceans—cover 40 percent of the Earth's surface and have long been considered biological deserts with stratified waters that contain very little nutrients to sustain life.

These regions also are thought to be remarkably stable, yet scientists have documented one anomaly in the North Pacific Subtropical Gyre ecosystem that has puzzled oceanographers for years: The region's chemistry changes periodically, especially levels of phosphorous and iron, affecting the overall nutrient composition and ultimately its biological productivity.

Study - Week - Proceedings - National - Academy

In a new study published this week in Proceedings of the National Academy of Sciences, researchers document what induces these variations: changes in the amount of iron that is deposited into the ocean via dust from Asia.

"We now know that these areas that were thought to be barren and stable are actually quite dynamic," said Ricardo Letelier, an Oregon State University biogeochemist and ecologist, who in collaboration with David Karl at the University of Hawaii led this study. "Since these areas cover so much of the Earth's surface, we need to know more about how they work in order to better predict how the system will respond to climate variations in the future."

Study - North - Pacific - Subtropical - Gyre

The study focused on the North Pacific Subtropical Gyre, and used three decades of observation data from Station ALOHA by the Hawaii Ocean Time-series program, which is funded by the National Science Foundation.

The surface layer of the North Pacific gyre is characterized by very clear waters with hardly any nutrients. The extraordinary optical clarity of these waters allows sunlight to penetrate deep into the water column and support photosynthetic activity below 100 meters (or 328 feet).

Ocean - Water - Column - Water - Waters

Typically, the ocean's upper water column is fertilized by nutrient-rich water mixing from the deep, but these waters are very stratified and little mixing takes place. Deeper water...
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