Taking the Temperature
06 September 2011 | Chukchi Sea
Lin came up with the string on a tin can idea for taking the temperature of the sea water. This is better than trying to drag the thermometer in the sea (it tends to hit the hull on waves) or using a bucket to get the water (if someone makes a mistake and doesn't haul the bucket up properly the handle tends to break off from the pressure of being dragged behind the boat). Collecting water by throwing a tin can over the side is easy, simple, and if anything goes wrong, there are other tin cans that could be used :).
We've been taking the sea temperature hourly (for logbook entries) and anytime we are in poor visibility (often) and wondering if ice is nearby. As I see it, a safe speed for being underway is one in which you can avoid hitting any ice you may come across. This depends on visibility (how close the ice is before it is seen) and boat speed. We slow down in poor visibility if we suspect ice is about (in more congested waters than the Chukchi Sea, slowing down in poor visibility is also done to avoid collisions with other vessels).
-1 degrees C is the coldest water temperature we've seen (sea water freezes at about -1.8 degrees C depending on salinity)--0 degrees C and +1 degrees C have been much more common.
For those familiar with boat electronics, yes, a depthsounder with a transducer that measured the sea temperature certainly seems like it would be a nice thing when sailing in cold water :).