Researchers using autonomous gliders discovered a significant phytoplankton bloom beneath the North Sea surface during a 2023 heat wave that satellite observations failed to capture.
Key facts
- •The study was led by the U.K.'s National Oceanography Centre in collaboration with Bangor University.
- •Autonomous ocean gliders provided continuous monitoring that traditional ship surveys and satellites could not replicate.
- •Phytoplankton concentrations during the heat wave were considerably higher than historical June observations for the region.
- •The subsurface bloom persisted for more than a week.
- •The research emphasizes the necessity of combining satellite data with autonomous technology to track climate impacts on marine ecosystems.
During an extreme marine heat wave in the North Sea in June 2023, researchers from the U.K.'s National Oceanography Centre (NOC) identified a massive biological response occurring below the ocean surface. While satellite data showed only minor changes, autonomous gliders revealed a sustained, intense increase in phytoplankton concentrations. The findings, published in Communications Earth & Environment, demonstrate that significant ecosystem shifts can remain hidden from space-based monitoring.
By the numbers
Subsurface Biological Response
Phytoplankton, which form the foundation of marine food webs, often congregate in a 'subsurface chlorophyll maximum' layer in stratified seas like the North Sea. During the June 2023 heat wave, concentrations in this layer rose significantly above typical levels of 1–2 milligrams per cubic meter. The glider data recorded sustained concentrations exceeding 3 milligrams per cubic meter, with short-lived peaks surpassing 9 milligrams per cubic meter.
Limitations of Satellite Monitoring
The study highlights a fundamental limitation of satellite technology, which can only observe the ocean surface. Researchers noted that the heat wave altered the layering of the water column, affecting the availability of light and dissolved nutrients. According to co-author Tom Rippeth of Bangor University, these changes in water column stratification are a primary factor in how marine life responds to heat waves, rather than temperature increases alone.
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This article was independently rewritten by ManyPress editorial AI from reporting originally published by Phys.org.
