Scotian Shelf Heats Up: Marine Heat Waves Intensify in Nova Scotia

According to a recent report by the European Union's marine monitoring service, the waters off Nova Scotia have been experiencing a concerning trend of gradual warming over the past three decades. The report, released on September 30, 2025, reveals that surface waters on the Scotian Shelf have risen by about 1.5 degrees, while the bottom waters have warmed twice as much, by approximately 3 degrees.

The team of scientists, led by Li Zhai from the Department of Fisheries and Oceans, found that the warming is primarily driven by longer and more intense marine heat waves, as well as fewer cold spells. At the bottom of the Scotian Shelf, the number of heat wave days has been rising by roughly 4 days per year, resulting in an additional 120 days of heat waves over the past 30 years.

The deeper layers of the Scotian Shelf are more strongly influenced by warm water intrusions from the Scotian Slope and Gulf Stream, which tend to linger longer than the surface temperatures. Meanwhile, cold intrusions and cold spells have become less frequent, causing the waters to not reset themselves between heat waves and leading to a gradual warming trend.

The warming waters are already affecting the species that live on or near the sea floor, including lobster. As the water temperature rises, lobsters become more active and need to eat more, which can lead to faster growth and larger catches in the short term. However, the report warns that continued warming could eventually push the conditions beyond the species' tolerance, as seen in southern New England where lobster stocks have declined.