Retractable Surface-Following Sampler

The design and use of a Retractable Surface-Following Sampler (RSFS) for chemical sampling, particularly of trace gases on depth scales smaller than the draft of the research platform, is discussed. The RSFS is compared to other vessel-tethered surface water sampling systems, such as buckets, bottes/rosettes, catamarans, hull intakes, and booms. The RSFS is a 5 m welded aluminum sampling boom with a hinge-mounted rolling trolley support at the inboard end; at the outboard end, floatation spheres support a scientific payload at fixed depths relative to the sea surface on an adjustable mount. The wheels of the trolley are confined in a deck-mounted track, allowing the boom to be quickly and easily deployed and retrieved using a pneumatic tugger, or fixed at an intermediate position that allows access for maintenance. Data and water sample lines from the instrument mount are secured within the boom, allowing continuous, controlled near-surface sampling at a distance from the ship's hull. Field data from a comparison of different water intake methods for carbon monoxide sampling, along with CTD and fluorometer data, exemplify typical uses of the system.