Argo profiling floats were deployed during the SIMBA cruise. A total of 23 floats were deployed along the cruise track from Punta Arenas to the Bellingshausen Sea. These floats drifted at a depth of 1000 meters; at 10-day intervals, each float sank to a depth of 2000 m and then ascended to the sea surface over a period of approximately 6 hours, collecting a CTD profile as it ascended. Many of ... the floats were also equipped with dissolved oxygen sensors. Once on the sea surface, the floats transmitted their data to a satellite and descended again to 1000 m to begin another 10-day cycle.
Each float was capable of collecting 200 or more profiles in this manner. The floats were equipped with ice-avoidance software in order to decrease the probability that they could be crushed by drifting ice while transmitting on the sea surface. As the floats ascended between depths of 50 and 30 meters, they examined the median temperature in this depth range; if the temperature was below a critical temperature that was indicative of ice cover above (chosen to be -1.77°C), the float turn off its buoyancy pump in order to stop its ascent. In such a case, the float decelerated and then stopped at a depth of about 3 meters; the float then stored the data collected and descended back to 1000 m. This process continued for as many profiles and 10-day intervals as necessary until the float was able to reach the sea surface, at which time it transmitted all stored profiles. Each float stored as many as 70 high-resolution profiles in this manner, or nearly 2 years’ worth of data. The floats all used the relatively high-bandwidth Iridium satellite system for communication. After the NB Palmer departed Punta Arenas, floats were deployed in Drake Passage and then along the ice edge, near the 2000 m isobath. A few floats were reprogrammed so that they can be deployed in shallower water on the shelf, where the ice cover is more permanent. Leading up to and during week 1 of field work (Sep 23-29) seventeen expendable bathythermographs (XBTs) were deployed in conjunction with 17 Argo floats between 62 south and 69S. The remaining floats were deployed in conjunction with a CTD cast from the vessel.