Initially a work crew gathers on the pier and on the bow and stern, in anticipation of what is about to occur. A few moments later there is static on the walkie-talkies. The hawsers come off the bollards and are pulled free; then, for an instant, nothing much happens. A moment later the unmistakable churning of the bow thruster can both be heard and felt through the gray drizzle, signaling that we are indeed getting underway. We have left the dock: cruise 17-01 of the research vessel/ice breaker Nathaniel B. Palmer has begun.
The weather around the port of Punta Arenas, Chile is calm, if not completely pleasant. It is December 24, one of the initial days of summer here, but the air temperature and precipitation are nearly identical to the conditions I left in Seattle a week ago, near the beginning of Northern Hemisphere winter. This Southern Ocean-inspired maritime climate is not likely an accurate preview of what is in store for us in a few days as we head south and west. The seas here are calm, but they won’t remain that way for long on our transit to higher southern latitudes. There is a persistent wind from the west that is likely to blow much stronger farther south. We’ll pass through Drake Passage on our journey, a legendary site of fierce winds and rough seas. Much awaits.
We are studying the Southern Ocean. There are three scientific groups aboard, exploring various aspects of the nature of this immense sea. We are not the first, and we won’t be the last, to do this; each expedition builds on the knowledge accumulated by the previous ones and helps to refine the scientific question addressed by subsequent ventures. Over many years our picture of the ocean has improved, helping us to understand the ocean’s role in climate, the carbon cycle, and the interactions between physics, chemistry, and biology.
What exactly does “studying the Southern Ocean” mean? It means collecting a set of observations of temperature and salinity that can be used to discern the actual circulation of the ocean; it means examining the carbon chemistry of the ocean, in order to assess sites where the ocean is removing CO2 from the atmosphere and places where instead it adds to the concentration overhead; it means sampling the microbiology of this ocean, to study the role played by physics and chemistry in determining the species assemblages and evolution of the phytoplankton and zooplankton in the region, the basis of the microbial food chain. And it means helping to use these observations to improve the state of climate models that can be used to examine the complexity of the behavior of the coupled atmosphere/ocean/cryosphere/biosphere where we live.
The Palmer is 308 feet long and displaces 6100 tons, and as such is one of the largest vessels in the US research fleet. Yet carrying out a scientific program from a single, minute spot in a vast ocean is not simple. Most of the equipment and supplies that are required for shipboard analyses must be brought from our laboratories in the US. In addition, there is a limit to what can be measured from a floating platform, the weather is always an issue, and there is a fixed amount of time that can be spent on any single task. In 24 days we will arrive at McMurdo Station, on the Antarctic continent south of New Zealand, where another scientific crew will take over on a new and different scientific mission. Our work is planned so that we can make the best use of our allotted time in order to study the ocean, and so that each group gets the share of time that it needs to complete its program.
For my own work, I will be deploying 12 biogeochemical profiling floats across the Southern Ocean as part of the SOCCOM program, a multi-institutional project that has been generously funded by the US National Science Foundation. Each of the floats carries a variety of sensors that can be used to infer physical and chemical parameters in the ocean. Unlike shipboard human samplers, the floats don’t care about wind, weather, ice, or perpetual day or night. If all goes well, each of these floats will sample the upper 2000 meters of the water column at 10-day intervals over the course of five years. The floats return their data via an Iridium satellite link, and the data are freely available on the Internet within day. At each deployment we’ll also lower a sophisticated shipboard instrument on a cable in order to collect data that can be used to calibrate the float sensors.
Spending the year-end holidays on a research vessel at sea in the Southern Ocean is a thought-provoking experience; there will surely be makeshift parties on board, but these are unlikely to be able to replace traditional celebrations back home. For now, newfound colleagues aboard the Palmer will serve as surrogate friends and family, bonded in the joy of our scientific effort and the motivation to better understand the workings of our planet.