In the Arctic the traditional summer melt is being fundamentally altered by a powerful, often hidden driver.
By Dr Bahareh Kamranzad, UArctic x Lloyd’s Register Foundation Research Fellow, Chancellor's Fellow, University of Strathclyde
While we often focus on atmospheric warming, the Arctic’s waters are experiencing climate change impacts more severely than almost any other open ocean. Among the most critical, yet understudied, phenomena are marine heatwaves; prolonged periods of abnormally high sea surface temperature at a location, lasting at least five days above the 95th percentile of long-term climatology. As these events become the “new normal,” they are not only reshaping Arctic ecosystems. They are also redrawing the map for Arctic shipping and redefining what safety means in a rapidly changing ocean.
The Mechanics of the Marine Heatwaves
Marine heatwaves typically peak during the summer. As sea ice retreats, darker ocean surfaces are exposed, absorbing more solar energy and reinforcing a feedback loop of warming and further ice loss. Recent research shows that these events are increasing in both frequency and intensity. At the same time, the way we define marine heatwaves is becoming increasingly inadequate. General definitions rely on long-term climatology, yet in the Arctic this baseline is shifting rapidly. Conditions that once appeared extreme are now occurring more often, even though their impacts on sea ice, ecosystems, and ocean dynamics remain profound.
Opportunity vs. Risk: The Shipping Dilemma
Decadal analyses of ocean conditions reveal a striking reality: in regions where summer ice was once permanent, ice concentration has now declined to near zero in recent decades. On the surface, this appears to create new opportunities for Arctic shipping. Marine heatwaves can open routes earlier in the year and extend the navigation season. However, this apparent accessibility comes with significant risks. Marine heatwaves can drive sudden and uneven reductions in ice thickness and concentration, creating highly unpredictable conditions. For vessels not designed or prepared for rapid transitions between ice-covered and open water, this unpredictability can lead to serious safety hazards. If Arctic development is to be sustainable, future shipping route planning must account not only for average conditions, but also for these compound and cascading impacts driven by extreme ocean warming.
Looking Ahead
As the Arctic continues to warm, marine heatwaves will play an increasingly central role in shaping navigational safety, environmental risk, and sustainable development. Understanding these events is not only a scientific challenge, but also a societal one. To benefit from new opportunities in the Arctic while avoiding preventable accidents and environmental harm, we must move beyond averages and begin planning explicitly for extremes. Marine heatwaves remind us that a more accessible Arctic is not necessarily a safer one, and that adaptation must keep pace with change. Achieving this will require collaboration across UArctic member institutions and beyond, to improve our understanding of climate-driven extremes at local and regional scales. As the ice retreats, our knowledge of the risks must advance even faster, protecting both the people who call the Arctic home and the fragile environments they depend on.
Photo: Bertelli fotografia/ Pexels
Funded by Lloyd's Register Foundation (LRF), the UArctic x LRF Research Fellowships support research projects through the joint initiative "Maritime Safety: Learning from the Past to Address Challenges to the Safety of Peoples in the Arctic". The initiative funds Research Fellows’ work across three themes: ice histories, safely navigating changing Arctic Sea routes, and cruise ships in the cold.
