NASA’s S-MODE Takes to the Air and Sea to Study Ocean Eddies

Using scientific instruments aboard a self-propelled ocean glider and several airplanes, this first deployment of the Sub-Mesoscale Ocean Dynamics Experiment (S-MODE) mission will deploy its suite of water- and air-borne instruments to ensure that they work together to show what’s happening just below the ocean’s surface. The full-fledged field campaign will begin in October 2021, with the aircraft based out of NASA’s Ames Research Center in Mountain View, California.

“This campaign in May is largely to compare different ways of measuring ocean surface currents so that we can have confidence in those measurements when we get to the pilot in October,” said Tom Farrar, associate scientist at the Woods Hole Oceanographic Institution in Massachusetts and principal investigator for S-MODE.

The S-MODE team hopes to learn more about small-scale movements of ocean water such as eddies. These whirlpools span about 6.2 miles or ten kilometers, slowly moving ocean water in a swirling pattern. Scientists think that these eddies play an important role in moving heat from the surface to the ocean layers below, and vice versa. In addition, the eddies may play a role in the exchange of heat, gases and nutrients between the ocean and Earth’s atmosphere. Understanding these small-scale eddies will help scientists better understand how Earth’s oceans slow down global climate change.

Sub-mesoscale ocean dynamics, like eddies and small currents, are responsible for the swirling pattern of these phytoplankton blooms (shown in green and light blue) in the South Atlantic Ocean on Jan. 5, 2021.
Credits: NASA’s Goddard Space Flight Center Ocean Color, using data from the NOAA-20 satellite and the joint NASA-NOAA Suomi NPP satellite.

The team is using a self-propelled commercial Wave Glider decked out with scientific instruments that can study the ocean from its surface. The most important gadgets aboard are the acoustic Doppler current profilers, which use sonar to measure water speed and gather information about the how fast the currents and eddies are moving, and in which direction. The glider also carries instruments to measure wind speed, air temperature and humidity, water temperature and salinity, and light and infrared radiation from the Sun.

“The wave glider looks like a surfboard with a big venetian blind under it,” said Farrar.

That “venetian blind” is submerged under the water, moving up and down with the ocean’s waves to propel the glider forward at about one mile per hour. In this way, the wave glider will be deployed from La Jolla, California, collecting data as it travels over 62 miles (100 kilometers) out into the ocean offshore of Santa Catalina Island.