We’ve made it to the last update for the cruise. Hard to believe we’ve finished up already! It will be nice to head back, see family members, and sleep in a real bed.
Updates from the final two cruise days are below. I’ve also included some information on what happens to the project now that the cruise is over. Thanks for following along with us on this adventure!
This was our final day to do science. In order to make it back to port in time, we needed to leave to head back between noon and 3pm.
So we started off the day as usual, with a CTD cast, followed by a trace metal CTD cast. The waves calmed down a bit from yesterday, but it was still rather rough while we were sampling.
|Last deployment of the trace metal CTD|
A common tradition on research vessels that do CTD work is to decorate styrofoam cups and send them down with the CTD. Depending on how deep the CTD goes, the cups are crushed by the pressure into miniature versions. If you do it right, mostly by stacking the cups together, they retain their original shape. Once the CTD comes back up, everyone has a personalized souvenir from the cruise.
|Decorated cups before going down with the CTD|
|Getting the shrunken cups out from the laundry bag that went down with the CTD|
Since we had time for another CTD cast, we attached our decorated styrofoam cups and sent it down to 2km. We tried to finish our typical sampling scheme by doing a PAR cast, but it ended up being too rough for that. The instrument kept getting pulled into the shadow of the boat, which, since we were measuring light through the water, would really throw off the results. It was also too rough to deploy the towfish.
|Our souvenirs with an original size cup in the back|
We finished up our final science day by retrieving the last drifter. Once drifters are in the water long enough, say a few days, they start to become a magnet for fish. Barnacles begin to grow on them, and where there’s a small organism, there’s a bigger one coming trying to eat it. The end result of which is that we tried to fish for a bit around the drifter before pulling it in. Saw lots of Mahi, and someone even had a small shark on a line for a bit, but we didn’t manage to catch anything. So we pulled in the drifter and headed for home.
|Pulling in the last drifter|
Today was our final day out at sea. It was a completely gorgeous day, sunny and calm. We alternated between packing up the labs and sitting out on deck enjoying the weather. A lot of the equipment had to be rinsed in fresh water and then dried before being stored, since saltwater is a strong corrosive. With the nice weather, we were able to get a lot of that done as well, which should help us load up faster once in port. We arrived back in Delaware at around midnight, signaling the official end to the cruise.
What happens next?
The cruise is now over, but the project we are all a part of will continue. It won’t be near as exciting as several weeks spent at sea, but this is where we make the work we’ve done collecting data matter. Since daily updates would become rather boring and meaningless at this point, I’d like to give you an idea of the next steps in the science process. Here’s what will happen:
Analysis. The first step is to continue the analysis we began on board. We have initial results from several experiments, but there are more to be run that we haven’t even started yet. They tend to be the ones that are more complicated and require either more time or different instruments.
We also have initial data from the CTD casts, the PAR casts, and the atmospheric chemistry measurements. All of these data have bad data points in the files, including points where the ship’s smoke stack interfered air measurements, or when the CTD recored weird temperatures and salinities before it entered the water.
Everything needs to be plotted in graphs and analyzed to see if it makes sense. If it looks good, then we start comparing various data sets to find relationships between them. Some of it may be causes and effects we expected to see, or we might find something new. Finally, we have to run statistics on it all to make sure what we find is significant, and not just lost in the error bars on the measurements.
Modeling. A major way we plan to use the data we gather, after it is processed and analyzed, is in models. The plan is to construct ocean and atmospheric models based on the conditions on our cruise. The models begin with basic equations representing physical, chemical, and biological processes. For example, there may be a gravity term, so that in the model, denser water and air will tend to sink below lighter water and air. Or a reproductive term, where if phytoplankton take up nutrients, the number of them will increase.
Then, we add in the information we get from the data. Based on what we found on the cruise, and the base equations of the model, we can figure out what is happening in the places or times we didn’t measure. We may also get a better idea of how the different pieces work together, and understand the processes that drive our results from measurements.
Writing papers. The final step in any project is to write scientific papers about the findings. None of what we do will ever be accepted until it is published in a peer-reviewed journal. This means that when we submit a paper to a journal, it goes out to other scientists to review before it is published. They look at the data, at your methods, and at the conclusions you drew from the work. If there are any mistakes, or it doesn’t look right, or you are missing something, they let you know. The paper won’t be published until it is fixed, or until you can successfully defend why you did what you did.
From this project, there will be a series of papers published. We don’t know what they will be just yet, but there will probably be several different types. For instance, there may be an overarching paper describing how all the different parts of the project work together to describe the influence of rain on the ocean. Each lab group may also have a paper or two on their specific part of the project. Another paper may describe the model and how it works. It is hard to tell ahead of time exactly what will be publishable and how to organize it into different papers.
Overall, the work to finish this project may take several years in total. In part, this is because different projects overlap. In order to keep the science going, a plan for a new project has to be submitted to a funding agency before the old project is over. Often, scientists will be writing the papers from the last project while collecting data for the next. Given that and the other responsibilities of scientists, who are often professors as well, it is no wonder the project will extend for so long past the end of the cruise.
|Farewell from the DANCE crew!|
This has been the final post on this research cruise. I hope you enjoyed following along with us as we traveled the high seas!