The earth is warming, but temperatures in the atmosphere and at the sea surface that steadily rose in the last half-century have leveled off and slowed in the past decade, causing the appearance of an imbalance in Earth’s heat budget. Scientists are looking into the deep ocean to determine where this additional heat energy could be stored, and recently traced a pathway that leads to the Indian Ocean.
If you want to understand Earth’s climate and how it changes from year-to-year and decade-to-decade, look to the oceans, and follow the heat. The major driver in the redistribution of heat around the globe in the ocean-climate system is Meridional Overturning Circulation, or MOC. The MOC is a vertical circulation pattern that exchanges surface and deep waters via poleward movement of surface waters. As an example, the well known Gulf Stream on the eastern seaboard of North America carries warm water northward to the Greenland and Norwegian Seas, where it cools and sinks.
Drifting buoys are a primary tool used by the oceanographic community to measure ocean surface circulation at unprecedented resolution. A drifter is composed of a surface float, which includes a transmitter to relay data via satellite, and a thermometer that reads temperature a few centimeters below the air-sea interface. The surface float is tethered to a holey sock drogue (a.k.a. “sea anchor”), centered at 15 m depth. The drifter follows the ocean surface current flow integrated over the drogue depth.