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Melting glaciers may eventually increase marine life

by Veronika Bryskiewicz Apr 1 / 13

Greenland is melting and larger than normal amounts of bioavailable iron are being released into the North Atlantic Ocean. Until now, meltwater from glaciers was considered to be too dilute to carry much iron. To date, only one other study examined the amount of iron in Greenland meltwater runoff, and it reported levels in the nanomolar range.

EX_Glacier2_HIRES
The “M” Glacier, one of the three glacial outflows sampled in this study. IMAGE: Sarah Das

A new study by Global Scholar Maya Bhatia (University of British Columbia) published in Nature Geoscience found that meltwater runoff from Greenland’s melting ice resulted in iron in the micromolar range – a thousand times higher than in the previous study. The result of this study may have implications for marine life, such as food supply and increasing algal blooms.

“In the open ocean, iron is found in a nanomolar range,” explains Dr. Bhatia. “Iron is a limiting nutrient, meaning that it limits by how much iron-consuming organisms can multiply. The North Atlantic is not generally considered to be iron limiting as wind-blown dust provides a source of bioavailable iron. However, recent work has shown that iron may be limiting to the organisms that consume it, like algae, at certain times of the year.”

But climate change and glacier melting is changing that.

Glaciers are porous with many well-like shafts called moulins and crevasses that allow melted water from the surface to drain to the base where it flows through a hydrological network of tunnels and channels, picking up sediment from the bedrock below. The more time the water spends flowing through the bedrock, the more iron it picks up. These meltwaters are then transferred by fast-moving streams that sweep the iron into the open ocean.

“Given that this is only the second such study to examine iron runoff, we still don’t have enough historical evidence to know what the baseline is,” says Dr. Bhatia. “Is this a significant source of iron to the ocean? What will be the ultimate effect? To answer these questions, we need to know how bioavailable it will be to marine life in the area. More studies need to be done. It’s an exciting new area of research.”

This work was funded by Woods Hole Oceanographic Institution, a private, not-for-profit organization on Cape Cod; the National Science Foundation; and by an American Geophysical Union Horton Hydrology grant.