1. La Nina: The East Sea is located in the North Pacific Ocean, which experienced a prolonged La Nina event during 2020 and 2021. La Nina is characterized by cooler-than-average sea surface temperatures in the central and eastern equatorial Pacific Ocean. This can lead to changes in atmospheric circulation patterns, including stronger trade winds, which can push warm water towards the western Pacific, including the East Sea.
2. Climate Change: Long-term climate change has caused a gradual increase in global ocean temperatures. This warming trend has been particularly pronounced in the East Sea, where sea surface temperatures have increased by approximately 1 degree Celsius (1.8 degrees Fahrenheit) since the late 19th century.
3. Local Oceanographic Conditions: The East Sea has unique oceanographic features that can amplify the effects of La Nina and climate change. For instance, the shallow waters and long coastline of the East Sea make it more susceptible to warming during La Nina events. Additionally, the presence of the Kuroshio Current, a strong ocean current that flows along the Japanese coast, can transport warm water into the East Sea.
4. Negative Feedback Loops: As the East Sea warms, it can trigger negative feedback loops that further amplify the marine heat wave. For example, warmer water holds less oxygen, which can stress marine organisms and make them more susceptible to disease. Additionally, coral reefs, which provide habitat and food for a diverse array of marine life, are highly sensitive to temperature changes and can bleach and die when exposed to prolonged heat stress.
The combination of these factors created the ideal conditions for a severe marine heat wave in the East Sea in 2021. The consequences of this event were far-reaching, causing extensive damage to marine ecosystems and fisheries and disrupting the livelihoods of coastal communities. As climate change continues to progress, the frequency and intensity of marine heat waves are expected to increase, posing significant threats to marine biodiversity and human societies.
