Ladies and Gentlemen- we made it to JUNE! Whew….we thought it would never come, but finally we are nearing the end. While we are fast approaching the end of our time out here, I wanted to share one more aspect of our work that I haven’t mentioned yet- floats!
For centuries, large-scale patterns of the ocean currents were deduced from the downstream fate of floatsam and debris of identifiable origin. That information combined with observations of ship drift provided rough estimates of ocean currents and transportation pathways. Luckily we have come a loooong way since those days and now we have many versions of autonomous sensors out there constantly providing us information about the world oceans. During our cruise we have deployed all kinds of autonomous instruments that we will reap benefits from for years to come including wave buoys, drifters, and Argo floats. They all collect data in a predictable and controlled manner and communicate in real time via satellite communications, providing significant contributions to our ability to model, understand, and describe global patterns both in the atmosphere and ocean. |
Drifter buoys have a relatively simple design- an antenna attached to a surface float, about half a meter in diameter and a holey sock that hangs down into the water column roughly 7 meters. The sock acts to capture the movements of the surface ocean currents. The buoys are tracked by satellites and send their location every hour. Deployment of these floats is quite simple. You take off the plastic wrap that holds it all together, and then chuck it into the water!
Using these satellite-tracked surface buoys, oceanographers are able to determine current speed and direction of surface ocean currents, as well as any other information from additional sensors the buoys are equipped with, which can include sea surface temperature and atmospheric pressure. Due to the high frequency of data transmissions, the resolution of data is much higher than many other floats. However, unlike the LADCP, which I am operating during the cruise, these drifters can only provide us with surface current measurements. These drifters are especially useful in very dynamic ocean current regions such as the Agulhas Current around the southern tip of Africa (my favorite current in fact!). In 2016, five drifters were deployed across the current with all five being deployed within a few hours of each other. Here is a map of where those drifters ended up- amazing to see how they all dispersed so quickly, with many of them getting caught in the eddy just east of the Agulhas Bank. |
ARGO is an international collaboration that collects high-quality temperature and salinity measurements in the top 2000m of the ice-free oceans. There are roughly 4,000 floats out there right now and many more deployed each month. Throughout this cruise we have deployed roughly a dozen ARGO floats and contributed to these international efforts.
Argo floats are different from drifters in that they descend 2000m and drift along with the deeper ocean currents. After about 10 days of drifting, they slowly return to the surface, collecting data along the way, and transmitting it all via satellite. ARGO floats have a lifetime of roughly 4 years however sometimes the instruments don’t last as long as intended. The Argo program has expanded and in recent years there have been projects focusing on Deep Argo, which would allow for the floats to descend to 6000m depth, and also BioArgo which are floats with additional instruments that can measure oxygen, chlorophyll, and pH among other variables. Each project has it’s own challenges but progress is being made every day so that we can learn more about the ocean. I have had the chance to be a contributor to deploying Argo floats on both my Pacific Ocean cruise in 2015 as well as my Indian Ocean cruise in 2016 (see post from I09 cruise). Over the years I have enjoyed keeping track of where “my” ARGO float have gone- take a look at where they are now! | We have had our final time-change onboard and are now counting down the days until we reach land. Spirits are still high and snacks are being shared freely as we all try to finish up the treats we brought with us to sea. We still have 8 more stations to go (at the least...things change every day) but the chatter has shifted to discussions of packing up equipment and flight departure times to get us back home. Hoping for continued smooth seas as we tackle these final days! |