Sea surface temperatures have a large influence on climate and weather. For example, every 3 to 7 years a wide swath of the Pacific Ocean along the equator warms by 2 to 3 degrees Celsius. This warming is a hallmark of the climate pattern El Niño, which changes rainfall patterns around the globe, causing heavy rainfall in the southern United States and severe drought in Australia, Indonesia, and southern Asia. On a smaller scale, ocean temperatures influence the development of tropical cyclones (hurricanes and typhoons), which draw energy from warm ocean waters to form and intensify.

These sea surface temperature maps are based on observations by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite. The satellite measures the temperature of the top millimeter of the ocean surface. In this map, the coolest waters appear in blue (approximately 2 degrees Celsius), and the warmest temperatures appear in pink-yellow (45 degrees Celsius). Landmasses and the large area of sea ice around Antarctica appear in shades of gray, indicating no data were collected.

The most obvious pattern shown in the time series is the year-round difference in sea surface temperatures between equatorial regions and the poles. Various warm and cool currents stand out even in monthly averages of sea surface temperature. A band of warm waters snakes up the East Coast of the United States and veers across the North Atlantic—the Gulf Stream.

Although short-lived weather events that influence ocean temperature are often washed out in monthly averages, a few events show up. For example, in December 2003, strong winds blew southwest from the Gulf of Mexico over Central America toward the Pacific Ocean, driving surface waters away from the coast, and allowing cold water from deeper in the ocean to well up to the surface. These winds are a recurring phenomenon in the area in the winter; they are known as Tehuano winds.