Along for the Ride

A CTD instrument is a standard workhorse of oceanography, measuring conductivity (salinity), temperature, and depth as it descends through the water. But this CTD has a special “passenger” attached to the right side of its rosette of sample bottles: a Channelized Optical System (CHANOS II). Developed by WHOI marine chemist Aleck Wang and his research team, the CHANOS II takes very precise measurements of dissolved inorganic carbon and the amount (partial pressure) of carbon dioxide in ocean water—two important factors in the global carbon cycle that helps regulate Earth’s climate. (Photo Mallory Ringham, Woods Hole Oceanographic Institution)