“In recent years large regions of unusually warm water have been observed in the global oceans.”

By John J. Hidore

Terrestrial heat waves have been a problem for the human species throughout history. They occur on all continents with the possible exception of Antarctica. Technically, they occur there as well. Terrestrial heat waves are defined as prolonged periods of unusually warm weather. What would be defined as a heat wave in one location would not be appropriate for another location, perhaps one not even too far away. An adequate definition might be, “A heat wave is an unusually warm or hot period lasting for days or perhaps weeks.” We associate them with summer but by this definition they can actually occur at any season. At least one country makes a clear definition of a heat wave and that is Pakistan. India defines heat waves and uses different temperatures in different parts of the country to establish what constitutes a heat wave. In the plains regions temperatures above 40 degrees C (104 degrees F) constitute a heat wave. They also define a severe heatwave for this region as experiencing temperatures over 46 degrees C (114.8 degrees F).

Marine heat waves

In recent years large regions of unusually warm water have been observed in the global oceans. These large areas of warmer than usual water develop when surface winds drop in velocity or become calm and are now referred to as marine heat waves. These large areas of unusually warm water(MHWs) are defined in similar terms to heat waves on land as prolonged periods of unusually warm water. In the United States NOAA defines a marine heat wave as an event where the surface water temperature is warmer than 90% of past events whose temperatures were warmer than average for that particular time of year and location for at least five days. The term” blob” has been applied to them. The term was the name given to an event that occurred off the west coast of the United States in 2014-2015.

Pacific Ocean Heat Wave of 2019

A marine heat wave developed over a large part of the northeastern Pacific Ocean this past summer. It extended from Hawaii to the Pacific coast of the United States and stretched all the way from Alaska to California. Temperatures off the coast here rose by 2-3 degrees Fahrenheit. Off the west coast of the United States the blob resulted in a large loss of marine life from microorganisms to large fish. It subsequently affected marine animals and birds. The Hawaiian Islands had the warmest summer on record this year. The effects of the current MHW had a major impact on life in the ocean near the islands. The warmer water resulting in extensive coral bleaching damage to the reefs.

These events are a product of the 21st century, occur in the oceans around the world and are occurring more often and are lasting longer.

Warming Ocean Temperatures

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