A recent study from the marine monitoring service of the European Union has revealed a gradual warming trend in the waters off Nova Scotia. This warming is attributed to longer and more intense marine heat waves and a decrease in cold spells, particularly impacting the waters near the ocean floor and the species inhabiting that environment.
According to Li Zhai, a scientist from the Department of Fisheries and Oceans who contributed to the 2025 Ocean State Report by the Copernicus Marine Service, the research team observed a warming pattern over the past three decades. Surface waters on the Scotian Shelf have increased by approximately 1.5 degrees, while bottom waters have warmed twice as much, by about three degrees.
Zhai emphasized the challenge of obtaining accurate below-surface temperature data due to limited observations, unlike the abundance of satellite data for surface temperatures. The report noted an increase in the number of marine heat wave days at the bottom of the Scotian Shelf, with approximately four additional heat wave days per year over the past 30 years, primarily attributed to climate change.
By analyzing data collected between 1993 and 2023 from the Bedford Institute of Oceanography and utilizing ocean model simulations by Copernicus, Zhai’s team gained a comprehensive understanding of marine heat waves across various depths, providing a detailed perspective on these extreme events in the ocean.
The study highlighted that while surface temperatures are influenced by seasonal variations in air temperature and weather patterns, deeper layers are more significantly impacted by warm water inflows from other regions, such as the Scotian Slope and Gulf Stream. This warm water, once it reaches depth, persists longer compared to surface temperatures.
Conversely, in the deeper layers of the Scotian Shelf from 2012 to 2023, cold intrusions and cold spells have become less frequent, leading to a lack of temperature reset between heat wave events and resulting in continuous warming of the waters.
Regarding the impact on marine life, Adam Cook, a DFO research scientist, noted that warming bottom waters are affecting species dwelling on or near the ocean floor, including lobster populations. The rise in water temperature causes lobsters to become more active, leading to increased feeding requirements and potentially influencing their growth rates and abundance.
While the current conditions in Nova Scotia remain favorable for lobster growth, continued warming poses long-term risks to the industry. Additionally, the report warned of the advantage warmer waters provide to invasive species, which could disrupt local ecosystems and fisheries, as seen in the Mediterranean with Atlantic blue crabs and fireworms.
Despite a slight cooling trend in 2023 off the Scotian Shelf, Zhai suggested that this was likely a temporary fluctuation within the gradual warming trend observed over the years. She emphasized the importance of considering short-term temperature variations alongside the long-term climate change impacts.
