IMPACT OF MARINE HEAT WAVES ON ARCTIC MAMMALS

GS3 ENVIRONMENT:

Recent studies highlight the severe impact of marine heat waves (MHWs) on marine mammals in Arctic and Subarctic regions. Rising ocean temperatures are increasing mortality rates, reducing reproductive success, and making these animals more vulnerable to diseases. The Arctic Ocean is expected to become a major hotspot for MHWs, defined as prolonged periods of sea surface temperatures (SST) exceeding historical norms.

About Marine Heat Waves

• MHWs occur when SST anomalies surpass the local 90th percentile for at least five consecutive days.
• They vary in scale, affecting areas from a few to thousands of kilometres.
• Studies in the Bering Sea and Barents Sea (key Arctic gateways) analyzed MHW events from 2014 to 2019.

Effects on Marine Mammals

• Species like narwhals and bowhead whales show delayed responses to MHWs due to their long lifespans and mobility.
• Their thick blubber provides insulation but can impair heat regulation during extreme temperature shifts.

Mortality Trends and Health Risks

• Increased mortality has been observed during prolonged warm periods.
• The Gulf of Alaska MHW (2014–2016) saw high mortality rates among humpback and fin whales.
• In 2024, the first recorded case of avian influenza in a polar bear raised concerns about disease transmission linked to MHWs.

Long-Term Ecological Implications

• MHWs can trigger toxic algal blooms, further endangering marine mammals.
• Population sizes and calf production rates decline, as seen in spotted seals of the Bering and Chukchi seas.

Behavioural Changes

• Some species alter foraging patterns or migrate northward, but Arctic residents lack this option.
• Changes in prey distribution can lead to increased entanglement in fishing gear, as seen in humpback whales shifting to southern fishing areas post-MHW.