Rescued Data Sheds Light on Arctic Climate Change

Microscopic algae are a key component of the Arctic marine ecosystem, but their role in the ecology of the Arctic Ocean may have been underestimated for decades, according to a research review published in December 2020. This discovery could be pivotal as scientists work to understand how carbon dioxide is removed from the atmosphere by living organisms.

Like terrestrial plants, marine phytoplankton, most of which are single-celled algae, use photosynthesis to turn light into chemical energy. They do this by consuming carbon dioxide and nutrients in the water and not only form the foundation of the marine food web but play a vital role in the carbon cycle.

Until roughly a decade ago, most scientists assumed that phytoplankton remained dormant throughout the winter and spring until sea ice break-up. Now, a new paper, which used historical data rescued by Bigelow Laboratory, suggests under-ice blooms of phytoplankton can flourish in low-light environments below sea ice.

“The Arctic is always alive,” said Bigelow Laboratory Senior Research Scientist Paty Matrai, a co-author on the paper published in the journal Frontiers in Marine Science. “Our research shows that there can be significant activity even when there is just a little bit of light.”

The revelation means that phytoplankton activity in some regions of the Arctic Ocean may be an order of magnitude greater than thought. That's important for scientists who study how much atmospheric carbon these algae absorb in order to understand our current and future climate.

Few places on Earth are transforming as rapidly as the Arctic. Over the past 30 years, the Arctic has warmed at roughly twice the rate of the global average. One of the most visible signs of that change has been in the decline of the sea ice, with this year's ice cover shrinking to the second lowest extent on record.

This thinning ice cover has helped phytoplankton to thrive in recent times, but Matrai helped illuminate evidence that winter phytoplankton blooms have long been a part of the Arctic.

Bigelow Laboratory Trustee Emeritus Spencer Apollonio conducted research on Arctic blooms in the 1950s and 1960s, but the data were lost in paper notes and files. Some were published, but remained in relative obscurity.

His findings demonstrated that blooms were occurring under thick ice in the central Arctic over 60 years ago. Matrai worked with Apollonio to rescue the data and integrate the research into the recently published review paper, which drew on several sources of historical data. The end result provided, what the authors called “an incredible first glimpse of under-ice phytoplankton blooms occurring in the central Arctic.”

Matrai says the next steps are to monitor these blooms with greater dedication. As sea ice thins and more light reaches the water beneath, the blooms may play an even greater role in the planet’s climate.

“The amount of carbon dioxide removed from the water may be significantly higher than what has been speculated,” she said. “If thinning sea ice increases biological activity under the ice, this region may take up even more carbon dioxide in the future.”

Photo: Gert van Dijken.