When the students of the science party were invited to participate in this cruise, we were told that our major responsibility would be serving as “watchstanders”. What exactly does that entail?
The Sikuliaq is a very new research vessel equipped with many means of analyzing the ocean and seafloor. It also sports a sophisticated and comprehensive shipboard computer network which archives all the data coming in from each of the various instruments. Each of these instruments is controlled by its own software, all of which can be viewed over the network. Still, they are not completely autonomous. Making sure that the instruments are calibrated correctly, not interfering with one another, properly accounting for the changing course and position of the ship itself, and turning in data that make sense is a full time responsibility. These duties are the constituents of watchstanding.
In order to give these tasks the round-the-clock coverage they require, the day is broken up into three watches. They are named by the “on watch” hours in each twelve-hour period: 12-4, 4-8, and 8-12. Each of these corresponds to a 24-hour schedule consisting of four hours of watch followed by eight hours off, followed by another four hour watch then another eight hour break.
Punctuality is paramount, and the further your shift is from your normal schedule, the more of an interesting and fun challenge this becomes. One way or another though, you’re up and ready to report to the computer lab ten minutes before your watch begins; you’re briefed by the previous shift’s watchstanders about the current conditions; and then it’s your turn to keep track of the ship’s course, instrument readouts, and other important events. The repository for this record keeping is the ship’s electronic logging system (E-log). Each time an instrument is turned on or off, or the ship changes course, or data collection is interrupted for any reason, it’s up to one of the watchstanders to create an E-log entry. The computer fills in the time and ship’s position (GPS coordinates), and the log entry is completed by selecting the relevant instrument and event type from a pair of menus, followed by a brief explanatory comment.
Watchstanding is not simply passive observation, however. Despite the sophistication of the instruments on board, some of them still require close supervision and occasional assistance. Most of this has to do with the depth of the ocean: the distance between the various sonars and the seafloor. The EM-302 (or “multibeam”) sonar can be given a maximum depth within which it should expect to find the bottom, as well as a more coarse-grained “ping mode” that ranges from auto (for waters up to 2500m) through “very deep” (2500-4500m) to “extra deep” (for depths >4500m). Similarly, the TOPAS sub-bottom profiler has a configurable trigger delay — the time between sending out a sonic pulse and beginning to listen for the return signal — which must be set so that, given the speed of sound through the water column and current the water depth, the instrument will be listening for the returning sound waves at the appropriate time.
Sometimes an entire watch will pass without requiring any adjustments. This is likely to happen when the ocean floor beneath the ship is flat, and the depth remains relatively consistent. Other times, we will pass over more varied topography and more attentiveness is required. The extreme case is passing directly over a sea mount (a submarine volcano): both instruments have to be gradually guided from a steady 5000-6000m up to a much shallower depth (depending on the particular mountain, up to a couple thousand meters above the surrounding seafloor) and back down.
The amount of hands-on assistance required by the instruments during a watch can be somewhat predicted by looking ahead on our course to see what the upcoming depth profile looks like. Other events, like rebooting instruments or unscheduled course corrections, are less predictable. By the end of each watch, there is at least one thing that is certain: next watch starts in eight hours. Time to go get some sleep; get some fresh air; work on your thesis? Probably get some sleep.