We are out at sea finally and after a couple days of all-around queasiness, we have all gotten settled into our lab spaces and learned our way around the ship. It has taken us 4 days of nonstop steaming (at 12.5 knots) to get to our first sample location. By the time I have enough internet saved up to post this blog, we will have already sampled our first station. After that, just 106 more stations to go! |
A little more background about what we are doing: we are currently steaming to reach a specific point in the ocean which is where the previous cruise ended their sampling 2 weeks ago. From there, we will head north along the 95E parallel for awhile before making a lefthand turn as we near the Bay of Bengal. We will then loop back north to finish sampling nearly all the way to the Asian continent. Onboard we are referring to this strange shiptrack as the “bowtie”. The reason behind it is that previous cruises (10, 20 years ago) did not do the exact route we are following, but instead did multiple shorter routes. We are therefore trying to re-occupy as much of the previous routes as possible, which is what the “bowtie” is allowing for. These cruises go out once every decade, and depending on many factors (weather, sea-state, available time/resources, and unforeseen incidents) sometimes they are not able to accomplish the planned route. By reoccupying the same route as previous cruises, we can begin to detect changes in the ocean state over these long timescales. The Indian Ocean is especially dynamic as it is influenced by both the El Nino/Southern Oscillation (ENSO effect) as well as the monsoons.
Our goal on this cruise is to sample the entire depth of the water column as accurately and consistently as possible. We do this by lowering our rosette into the water with a winch, and allowing it to lower all the way down to just above the surface. Instruments on the rosette are constantly taking measurements during the descent. Once we are hovering just above the ocean bottom we begin to capture water samples using the Niskin bottles that are on the rosette. Onboard this vessel our rosette has 36 Niskin bottles, which means that we can capture water from 36 different depths as we bring the “package” (i.e. the rosette and all the instruments) back to the surface. The increase in bottles from 24 on most cruises to 36 onboard the Revelle means that we spend a little more time at each station and also that there is 50% more work to do to run samples. It will definitely be a busy cruise! |
We have already been trained on how to set up the rosette, making sure all the bottles are secured in the open position and that all instruments are turned on before deploying the package. My job in the computer room then is to monitor the sensors on the way down and then close or “fire” the bottles at the desired depths as we come back up to the surface. The most stressful part of my job is that I cannot let the rosette hit the bottom of the ocean. The winch is sending out cable at 60m/min until we approach the bottom when they slow down to 30m/min. Typically we have an altimeter on the rosette that begins alerting us when we are within 100m of the ocean bottom. However, due to the loss of a rosette on the previous leg of this cruise, we are working with our backup altimeter which means we will only get a 30m warning before hitting the bottom. Talk about stress! |
During this downtime as we motor to our first station I have been keeping busy with creating an automatic program to plot our location, our completed stations, and projected route onto wind and wave forecast maps for the Indian Ocean so we can see what we will be encountering over the coming days at sea. I finally got the script up and running- we have low winds and small waves in our 3 day forecast!