A July 2018 phytoplankton bloom in the Barents Sea, an increasingly common occurrence.
Image: NASA Earth Observatory

Thanks to climate change, the Arctic is becoming a deeply weird place from polar bears chowing down on whale carcasses to a microplastic invasion. A new study adds to the mountain of evidence that the region could be transformed within our lifetimes.

As sea ice recedes, the colorful spring phytoplankton blooms that dot the Arctic are becoming more vigorous and appearing at higher latitudes than ever before. The results, published this week in Geophysical Research Letters, showcase changes happening at the base of the food chain. How that propagates upward will have vast ramifications for the warmer, low-ice Arctic of the future.

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Arctic sea ice hits its peak in February or March before receding toward a minimum in September. As the ice crawls back to the high Arctic and more sunlight reaches the open water, phytoplankton blooms appear on the surface for a few weeks each spring across the seas that ring the Arctic Ocean. Those bloom can account for half of all primary productivity—basically plant growth—in the Arctic, so even though the blooms are short-lived, they’re an essential ingredient for life.

But climate change has caused sea ice to drop precipitously, leaving more water exposed earlier and earlier in the year. That led researchers to ask whether plankton blooms were changing in response to receding ice. To find out, they analyzed 10 years of satellite data spanning 2003-2013. Because the blooms stand out sharply against the dark water and white ice, they were able use ocean color data.

The results show primary productivity across the Arctic rose an astonishing 31 percent over the 10 years of data. Notably, they show that phytoplankton blooms are occurring at higher latitudes in waters that were previously ice covered or inhospitable because of their low nutrient content.

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“We were not expecting to see phytoplankton spring blooms in the central basin,” a region above 80 degrees north, Sophie Renaut, a PhD student at the University of Laval who led the research, told Earther.

The results also show that primary productivity is increasing, particularly in the Barents and Karas Seas that border the North Atlantic. That region has seen some of the greatest sea ice declines and warmer Atlantic water streaming into the area. Renaut said that while the results of the new study don’t necessarily add more evidence to the “Atlantification” process playing out, she said the intrusion of water waters is “strongly impacting the retreat of the ice cover in this region, and consequently the organisms living in these waters.”

The increase in spring phytoplankton productivity is both a symptom of rapid warming and disappearing ice and a potential cause of new changes, especially as the Arctic moves closer toward ice-free summers in the coming decades. Scientists don’t wholly know what that will mean for the delicate ecological balances that have evolved over millennia.

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Renaut pointed to a potential mismatch between when and where phytoplankton blooms occur and when and where the tiny animals that graze on them, called zooplankton, are active. That’s just one potential impact that could ripple up the food chain.  

“It is difficult to say how other organisms are going to adapt to these changes,” she said.