Scientists have discovered that levels of the naturally-occurring isotope radium-228 have almost doubled in the middle of the Arctic Ocean in the last 10 years. The study illustrates once more that a warming climate is having a far-reaching effect on Arctic ecosystems.
The findings — published this week in the journal Science Advances — show that significant changes are occurring along the region’s coastlines, because the source of the radium is the land and continental shelves around the ocean.
The research team, led by Woods Hole Oceanographic Institution, thinks that the Arctic’s rapidly melting sea ice has resulted in more open water near the coasts, thereby allowing winds to create waves. These waves then churn up sediments on the shallow shelves, releasing radium that is carried to the water’s surface and into the open ocean.
This process is also likely to deliver additional nutrients, carbon, and chemicals into the Arctic Ocean — fuelling the growth of plankton and impacting fish and marine mammals higher up the food chain.
Researchers measured radium at 69 locations from the western edge of the Arctic Ocean to the North Pole on a two-month excursion on the icebreaker Healy in summer 2015. They found that radium-228 concentrations in the area had skyrocketed since measurements were last taken eight years prior.
Upon investigation, they discovered that ice and water were flowing northward from the northern coast of Russia toward the middle of the Arctic Ocean, where radium levels had increased.
They concluded that the radium had originated in sediments from the East Siberian Arctic Shelf, which is shallow, but extends 930 miles offshore and is known to contain large concentrations of radium and other chemical compounds.
However, the researchers believe there could be other factors behind the increased radium levels. Greater wave action can lead to coastline erosion, which adds terrestrial sediment into the ocean. Warmer temperatures can melt permafrost, leading to river and groundwater runoff that also carries material into the Arctic Ocean.
“Continued monitoring of shelf inputs to Arctic surface waters is therefore vital to understand how the changing climate will affect the chemistry, biology, and economic resources of the Arctic Ocean,” wrote the authors of the study.