As climate change continues to grip the Arctic—causing the oceans to rise, permafrost to thaw and sea ice to melt—scientists believe they've discovered an unexpected consequence of the shifting landscape. Changes along the coastline are altering the composition of the Arctic Ocean, in ways that could fundamentally transform the local food chain.
A new study published yesterday in the journal Science Advances suggests that there's been an increase in the amount of soils or sediments flowing from the Arctic shore into the ocean over the last decade. And the researchers say climate change is likely to blame. As Arctic sea ice continues to melt, it's exposing the shallow regions around the coast to more wind and wave action, causing the waters to churn and draw sediments up from the continental shelf into the water column.
These sediments have likely carried an influx of carbon and other nutrients with them, which—if the pattern continues—could fuel an increase in plankton and algae in the water. And because plankton are a major food source for small fish and other marine organisms, the shift could cause a major change in the numbers and types of animals that populate the region.
It's hard to say how these changes might affect the Arctic ecosystem as a whole, said Matthew Charette, a scientist at the Woods Hole Oceanographic Institution and one of the study's authors. There could be both positive and negative effects.
"You take away ice, you take away potential habitats for polar bears," he noted. "But then that may in turn lead to increases in fish stocks, for example, if you have increases at the base of the food chain."
The researchers—scientists from Woods Hole, the University of South Carolina and the University of Washington—came to their conclusions by measuring radium isotopes in the Arctic waters. Radium is a chemical element found in soils and sediments, including in permafrost, in riverbeds and on the continental shelf around the Arctic shoreline. It dissolves easily in seawater, making it a reliable indicator of any increases or decreases in the amount of sediment flowing into the water over time.
The researchers compared two data sets of radium measurements—one collected by another research group in 2007, and one that they collected themselves in 2015. They found that there was a significant increase in radium from the first data set to the second. As a result, the researchers can infer that there's been an increase in the amount of sediment—along with the carbon and nutrients it also contains—into the ocean.
The spike in radium-containing sediments could potentially have come from a variety of sources, the scientists noted. But the balance between the different isotopes, or chemical forms, of radium they've measured so far seems to suggest that the recent increase is mainly coming from the continental shelf, likely thanks to reductions in sea ice. But in the future, other climate effects—such as thawing permafrost—could release more sediments from other sources into the sea.
As a result, the scientists believe the pattern they've observed so far may continue as the Arctic goes on warming. But the only way to be sure is to continue monitoring different parts of the Arctic coastline.
"The most extensive data that we have was just for those two data points, and it's hard to make a projection based on drawing a line between two sets of data," Charette pointed out. "If you consider the 2007 data as a kind of a baseline, and then what we got in 2015—if we can add to that, we can better predict which direction things might be heading."
Reprinted from Climatewire with permission from E&E News. E&E provides daily coverage of essential energy and environmental news at www.eenews.net.