Alex’s RV Investigator blog
The Slow Journey South
Here we are on the Australian Research Vessel Investigator in the great swells of the Southern Ocean. It is day 33 of 43. We are 65 degrees South, 132 degrees East, and about 100 km north of the Antarctic coastline. To get here we have passed through the roaring forties and furious fifties and entered into the screaming sixties – regions of wild winds that circle the Southern Ocean unimpeded by land. If you pan over this spot in Google Earth you won’t find much beyond a large expanse of seemingly empty ocean. That begs the question: What on Earth are we doing out here?
The practical motivation is science. We have two main teams of scientists on-board, an atmosphere team and an ocean team. One team looking up. One team looking down. The atmosphere team, myself included, has their heads in the clouds. We’re looking up with various lasers, radars, air samplers and weather balloons filled with helium to better understand how this remote ocean environment helps with the formation of clouds – a process of the climate system we know little about. The ocean team is casting equipment into the depths to take measurements of different ocean layers. These deep ocean layers contain water that may have been cut off from the atmosphere for hundreds if not thousands of years. They measure all sorts of different physical and biological properties such as temperature, oxygen, nutrients, carbon, trace metals, chlorophyll and much more. This is a continuation of a dataset that extends back to 1991.
The ocean team set out a long list of locations where they wanted to cast their lines. Upon reaching each location, we sit and wait while the instruments drop down to ocean bottom (sometimes over four kilometers down) and come back up again with samples of water throughout the profile. This means we spend many hours bobbing up and down in the water sitting, waiting and then sampling. The journey south to the Antarctic ice edge, which could take just five days, therefore took us twenty-two days.
The Southern Ocean provides us with a unique natural laboratory that gives an insight into how things might have been before the industrial era. It is a pristine environment that is largely out of reach from human influence and any influence from the land. However, measurements of the ocean and atmosphere in this part of the world are few and far between. Our limited knowledge of this environment is a major concern for climate modelers. In particular, it’s the curious clouds that draw our attention.
This unique environment produces some unique clouds. Over land, as water builds up in a cloud it will typically condense on a tiny particle (an aerosol), start to grow, get heavy and fall back toward the Earth. If it’s cold enough, the water will condense on an aerosol and freeze forming a snowflake. Out here, the air is so clean that the water has very few aerosols to condense upon. This means that the clouds can live for long periods of time without raining out. It also means that many clouds out here are made up of super-cooled liquid water i.e. they are a liquid at sub-zero temperatures.
We also think that there are some curious interactions between marine biology and cloud formation. The phytoplankton that form the base of the Antarctic food web and that attract so much wildlife, like krill and whales and seals and birds, also produce some natural aerosols (e.g. sulfur containing compounds). These aerosols can be carried up into the atmosphere and help to form clouds. It’s an intriguing connection between marine life, clouds and the climate that forms a key component of the well-known Gaia hypothesis.
These complicated interactions between the marine biology, aerosols, clouds and climate are exactly what we’re out here to better understand. This will hopefully help us resolve some issues that climate models have over this region. Our campaign therefore includes an assault on the atmosphere using ship-based, aircraft and satellite instruments. The aircraft, a Gulfstream V from the US National Centre for Atmospheric Research (NOAA), has been flying south from Hobart through these super-cooled liquid clouds to measure their unique properties. The satellites, in particular CALIPSO and CloudSat, provide a broad overview of the region and fill in the gaps where the aircraft and ship don’t reach.
So that’s the practical motivation. If that’s not enough, I think most people on-board agree that this journey is just as much about the experience of adventure and novelty. Life on the ship is new to me. Thankfully the Investigator is well equipped, well crewed and perhaps most importantly for this neophyte well balanced in the big swell of the Southern Ocean. A good routine helps to adjust quickly. Wake, eat, check the instruments, get some fresh air, eat, process data, gym, write, table tennis, eat, share stories, sea sickness tablet, sleep, repeat. Beyond the routine it’s the unique people and the spectacular view that keep things really interesting. And we’ve seen breathtaking sights that few have ever seen before.
Despite having some of the harshest living conditions on Earth these waters are highly productive and are absolutely teaming with life. We’re in the peak of summer right now, which means an influx of marine mammals and birds. Just today we saw a pod of at least a dozen orcas, with juveniles in tow. Four days ago we saw a pod of at least thirty pilot whales, big black melon-headed whales. We see humpbacks on almost a daily basis. If we’re lucky we’ll spot some penguins or a seal out on the sea ice. All sorts of birds circle the ship, dipping and gliding over the swell of the sea: Royal albatross, black-browed albatross, sootie albatross, snow petrels, cape petrels and many more. This spectacle of nature brings about wonder in us all. To make it even better, it’s set upon the backdrop of icebergs and sea ice and (if we’re lucky) a wondrous drawn-out polar sunset.
After a few more stops we’ll be on our way back to Hobart to end this six-week journey. The scientists will collate their data and share their ideas. With luck and hard work this will lead to a better understanding of this phenomenally complex and wondrous environment.