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River Science: Water Temperature

The Hudson River's depth fluctuates wildly as one sails up its length. In many places, most notably just off West Point, the water is so deep that its ambient temperature often varies considerably between the bottom and the surface.

Although water temperature has relatively little effect on the Half Moon or its crew (with the exception of extreme temperatures, as Captain Hudson understood while battling the polar ice during his arctic expeditions), it can have obvious effects on the local ecology.

On the Half Moon, our students take temperature readings both from samples drawn from the surface (usually as part of comparative temperature studies), and from the water column, which means water collected from different depths at a single location.

To measure ambient temperatures within the water column, we use a Van Dorn sampler (now known more commonly simply as a water sampler). This hollow tube can be lowered to a desired depth in the water. A brass weight is then dropped down an attached line, producing a minor jolt when it reaches the sampler. This bump snaps the tube shut, trapping a water sample inside, which can then be retrieved for analysis.

On this Voyage of Discovery, no students specifically studied temperature within the water column for their projects, but whenever the ship was stationary, we still took readings for the Deck Log.

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