After a few days of slaving away inside a shed in Gisborne, Andrea Ogston and Dan Nowacki from the University of Washington have downloaded all the previous tripod data, cleaned the various instrument, reinstalled new batteries and reprogrammed the sensors for the next period of measurements. This was an impressive amount of work, but they were able to get it all done because of their considerable experience at this type of work. We were excited to find out that we received lots of great data from the second deployment. For example, I quickly made a preliminary plots of bed elevation changes and wave heights at the “depocenter” site, and it appears that many large wave events (>5 m or 15ft wave heights) occurred over the last few months causing significant (~3 cm) erosion. This was a surprising result as this is a location where long-term sediment accumulation is know to occur. The data collected will provide us with valuable new insights into sediment dynamics seaward of the Waipaoa River.
We were fortunate to have great weather on the day we needed to redeploy the tripods. So, after some quick checks and adjustments, the pods were lowered to the seafloor. This is a somewhat delicate operation as we need to carefully place the expensive, instrumented systems right-side up on the ocean bottom about 40-60 m (120-180 ft) below. For the first two tripods, we used one of the acoustic releases to detach the pods when they hit the bottom, but for the third we needed to use a slip-ring system, where someone on the ship pulls on a line when the tripod reaches the bottom (see picture of Rip and UW team). This is particularly challenging and potentially dangerous in rough weather, but it went without troubles for us thanks to the small sea conditions.