Sea surface temperature is the measure of the water’s temperature at the ocean’s surface. The temperature of the ocean varies primarily with latitude. The warmest waters generally occur along the equator and the coolest near the poles. Most deviations from this pattern occur due to the ocean’s currents. For example, you can see warm water moving north along the eastern coast of the United States due to the Gulf Stream current, and water along the western coast of the U.S. is cooler than you might predict due to the cold water upwelling. What other deviations from the pattern do you see?

Sea surface temperature is measured by satellite instruments that record the energy emanating from the ocean surface globally. The energy is emitted at different wavelengths. The data are then validated with temperature readings collected by ships and buoys. Computers then process and smooth the data according to algorithms written by scientists.

Understanding sea surface temperature is important because it helps us understand why some places are warmer or cooler and how that impacts the species living there. Changes in an organism's environment can impact its access to food, alter migration patterns, or change access to mates.

Additionally, as Earth warms much of the excess heat is being absorbed by the ocean causing an increase in sea surface temperatures. The National Oceanic and Atmospheric Administration (NOAA) has collected data showing the ocean has warmed approximately 0.13℃ (0.234℉) every 10 years over the last century. This can change the range of marine organisms and bleach corals. It also impacts the amount of water vapor available to weather systems increasing the chances for more severe and stronger events. Warmer waters can even change the trajectory of a storm, flooding unprepared places and causing droughts in other locations.

These sea surface temperature map layers are composed of radiance measurements collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on the National Aeronautics and Space Administration (NASA) Terra and Aqua satellites. The temperature of the top millimeter of water was measured in Celsius and is accurate within half a degree. These map layers show the average sea surface temperature for the months of March, June, September, and December 2020 at a one-degree resolution. Compare these layers to one of the other sea surface temperature layers to see how sea surface temperature changed seasonally in 2020. Next, add the ocean currents map layer, what do you see?