Warmer oceans put coastal communities at risk, increase infrastructure costs, endanger polar creatures and threaten coral reefs and fisheries. Perhaps most alarmingly, rising ocean temperatures accelerate the overall warming trend.
See how rising ocean temperature has killed off coral reefs in the Florida Keys—and find other hot spots threatened by higher air temperature on the Climate Hot Map.
Not only are ocean surface waters getting warmer, but so is water 1,500 feet below the surface. These increases in temperature lie well outside the bounds of natural variation.
In fact, the ocean has absorbed so much heat—about 20 times as much as the atmosphere over the past half-century—that some models suggest that it is likely to warm the air another degree Fahrenheit (0.55° Celsius) worldwide over the coming decades.
Although ocean temperatures are more difficult to measure than land temperatures, scientists can use several methods to create an extensive ocean record.
- Dropped from ships or airplanes, probes gauging the ocean's conductivity, temperature, and density provide nearly continuous surface-to-bottom measurements at specific times. However, these probes rarely reoccupy an exact location.
- Remote vehicles can measure the temperature of deep ocean waters, and periodically surface to transfer the information to satellites.
- Moorings on the ocean bottom can measure temperatures at fixed distances above the bottom, until a ship retrieves the instruments—typically after a few months or years.
- The most common measurements, however, are taken at the sea surface. Scientists combine these measurements with land surface measurements to calculate the global average temperature.
- Scientists also know that ocean temperatures are rising because warm-water species are moving into areas that were formerly too cold, while cool-water and cold-water species are likewise on the move.