Time and Motion

Almost home…
0700 EST
41° 29.558’N, 70° 40.751’ W
Winds: 8 knots
Sea Surface Temperature: 66°F

Something woke me from a deep sleep at 0500 EST. It was something we had not known for many days. It was stillness. We had been transiting through a gale for almost two days and suddenly all was calm. I walked up to the bridge and fixed upon a light slowly flashing far away through the fog. We were almost home, and the peaceful sounds of Van Morrison’s “Into the Mystic” began to play in my mind.

The sea fought us for two days. Winds exceeded 40 knots. Waves pushed us back. Periodically, we made 4 knots at best—moving only 4 nautical miles closer to home for every hour that three diesel electric engines hummed below the waterline. Pizza for dinner, two Meclizine for desert, and then quick preparations for a long nap. This included filling a water bottle (you don’t know how long you’ll want to stay in bed), grabbing a good book, and then stuffing extra blankets under the side of the mattress. The latter curls the bed and keeps you off the floor. It may reduce the startling sensation of falling out of bed, but it does not reduce the sensation of falling out of the sky. Of countless such experiences, three were particularly memorable. Laying in darkness, head to the bow, feet to the stern, I would try to visualize our ship from above and the seas that were shoving it. Were we crossing the swell at an angle? That would explain the roll associated with the pitch. Was the wavelength close to the length of the ship? That would explain the regular rise and fall of Atlantis. Were we headed straight into it? That would explain ferocity. There was comfort in predictable regularity, and I nearly drifted to sleep. Then we began to fall. Faster. Head first. We crashed into the trough and the hull rang explosively. A bomb could have detonated under the deck and I wouldn’t have known the difference. According to our third mate, Kami, the wave “was taller than the house. The bow went under, and it knocked the phones out of their cradles.” Three times.

We were able to grab one last multi-core before the transit, but had to forgo two stations. Such is the nature of oceanography. The gaps in our data, and ultimately in our knowledge, are frequently driven by the temperament of our Planet. But in the end, we successfully sampled the majority of our proposed stations and all of our high priority stations. It is hard to believe that so much has happened and 26 days have passed. Does this mean it is over? Not hardly. Our immediate future involves unloading the ship, storing and properly cataloguing our samples in the libraries at WHOI, paperwork, etc… It also involves taking a moment to thank the wonderful crew, to step off the gangway, and to look back on the incredible machine we called home for one month: Atlantis. Followed by properly unwinding, of course.

A new adventure awaits on land—one in which we read aloud the messages stored in our bottles.

Many Hats

Station 18
0656 EST
37° 28.181’ N, 74° 14.403’ W
Winds:11.6 knots
Sea Surface Temperature: 71°F

Before leaving Station 17 yesterday, we completed 4 CTD casts, deployed a sediment trap array, and recovered cores from the bottom of the sea. Sunrise came as Maureen Soon of University of British Columbia, Joe Murray of WHOI, Atlantis' SSSG Alison Heater, and winch operator “Catfish” (not shown) worked together to bring the CTD safely back on deck (see photo). The sediment trap deployment (see second photo) was a bigger show, and required many more people on hand to do it safely. Scientists and crew worked together to build a 2 km long chain of glass ball floats (in protective yellow plasticmolding), wire, three sediments traps (large yellow funnels), and an anchor system. It is out there now and will remain hidden from the sun for one year. During that time, particles will quietly sink into each trap and collect into a bottle at it's base. An empty bottle will rotate into position every two weeks, thus separating 1 year’s worth of sinking particles into 24 discrete samples. Next year we will steam back to this station, place a speaker beneath the ubiquitous waves, broadcast an acoustic signal that releases the anchor and call the traps home. Hopefully.

Traps like ours are perhaps the most common means for long-term chemical analyses of sinking particles. However, particles sinking at an angle, like blowing rain, are less likely to enter the trap and can result in an underestimation of the sinking particle flux. This artifact can be constrained by a very clever system of geochemical tracers: Uranium and Thorium. Uranium-238 is a very long-lived (4.5 billion year half-life) radioactive isotope that decays to become the very short-lived “daughter” Thorium-234 (24 day half-life). While Uranium-238 is more-or-less uniformly dissolved throughout the ocean, Thorium-234 is very “sticky” and can be readily swept away by sinking particles. Therefore, we can infer particle fluxes based on variations in the concentration of Thorium-234 relative to Uranium-238 in the water column. This is one example of the variety of techniques that we are employing to understand our planet. It is also one example of what lured me into marine science—the opportunity to wear many hats.

As marine scientists, we must be chemists, biologists, and physicists. We engineer and machine our own instruments. We employ a variety of analyses, including those of the mathematical persuasion. And we better know a bowline from clove hitch. But we are only one part of the scientific endeavor on Atlantis. Look again at today’s photos. Scientists and crew don hard-hats, share their skills, and work together on the deck in spirited teamwork to get the job done.

For more hats, please visit the following links:

• Café Thorium – Ken Buesseler’s radiochemistry group at WHOI
• Atlantis crew member, Lance Wills, throws his second hat into the ring with these incredible photographs
  

Hiatus

Station 17
36° 41.372’ N, 73° 28.074’ W
02:20 EST
Winds: 37 knots, gusts to 45 knots
Sea Surface Temperature: 73°F

We are situated at the convergence of a tropical low-pressure center migrating Northward and a cold front marching Eastward. They act in concert to pitch 40 knot winds and 18 foot swells. We are rocking, cabinets are creaking, and waves intermittently slap the iron hull like cars hitting a barricade. We are holding station and our work is on hiatus. We only have a few days left to complete a rather ambitious agenda: 2 kilometers of sediment traps, multiple CTD casts, in situ pumping casts, and sediment coring.

When weather gets rough like this, the science party has three primary concerns: 1) securing samples and gear, 2) helping each other as needed, 3) and considering contingency plans that will maximize the scientific value of our limited time at sea. After that we can rest, lay down, and watch a movie while riding out the storm. We are lucky.

The crew of Atlantis is not. They do not go on hiatus when the seas are rough. Whether in the heat of the engine room or high on the bridge, they continue to keep us safe, healthy, and productive. Without them, oceanography would be purely theoretical. For all this and more, we are grateful to the crew of the R/V Atlantis. With their help, our science objectives will be met before steaming into port on Tuesday.


* For real-time marine conditions near Station 17, visit NOAA's National Buoy Data Center, Station 41001

Under Pressure

Station 15
34° 38.463’N, 71° 29.960’ W
14:25 EST
Winds: 8 knots
Sea Surface Temperature: 82°F

We arrived at Station 15 yesterday under clear skies, over blue water, and through strings of bright yellow sargassum as long as our ship. Flying fish soar through the air (occasionally onto our deck) and sea spray encrusts our gear with coarse grains of salt. The sun is shining today on the deepest station of our final transect across the continental slope. The remaining stations will take us ever closer to our homes.

Although the transit to Station 15 offered several hours reprieve from sampling, it did not relieve us from sample processing. For example, WHOI’s Paul Morris is examining the distributions of Radium and Thorium in seawater. One of four isotopes of interest, Radium-224, has a half-life of 3.66 days and will decay to an undetectable abundance within weeks of sampling. If it isn’t measured now, it won’t be measured at all. Katherine Hoering and Kristin Luttazi have been quantifying the abundance of dissolved inorganic carbon (“DIC”, think baking soda dissolved in water) around the clock, trying to keep pace with influx of newly retrieved samples. Other scientists, such Drew Snauffer from the University of British Columbia, have been preparing their samples for long-term storage by filtering and acidifying large-volumes of water (20 liters each). Long hours, intermittent sleep, and focused work are essential to the success of this very expensive endeavor.

Amid the rush to complete our tasks, we do find time to decompress. Our teams have been sharing many laughs, songs, movies, and good meals (have I mentioned how good the food is?). Morale is high, thanks largely to our chief scientist, Tim Eglinton, and the tremendously supportive crew on Atlantis. Our spirits are also indebted to the juxtaposition of our innate curiosity about the natural world and oceanographic traditions. For example, have you ever wondered what the weight of the ocean could do to a Styrofoam cup? The tiny air pockets are no match for the pressure at 4500 m depth (deeper beneath the waves than the summit of Mt. Whitney rises above sea level) and the cup is squeezed into a distorted miniature version of itself (see photos of a cup before (above) and after (below) traveling to the bottom of the sea aboard our CTD). What kinds of life can exist under such extreme pressure? How does it affect the chemical composition of the sea? How sensitive is it to change over geologic time scales? Questions like these drive our work. Camaraderie, this incredible environment, and Stryofoam cups help us endure the pressures.

Wanderers

Station 14
37° 41.713’ N, 68° 28.402’ W
04:19 EST
Winds: 19 knots
Sea Surface Temperature: 80°F

The CTD was in the water and we were in the computer lab operating the winch. Kilometers of wire unspooled on a video monitor and data streamed across our computer monitors. At night, against the backdrop of a black sea, Atlantis’ machinery appears to float in empty space. But not tonight. Something was different. Something barely perceptible on the video monitor was moving outside. Something big. I opened the door and walked onto the back deck. The ship’s frame obscured my view. I walked further and turned around. And there they were. Three giants reflected in the water.

There is nothing quite like moonlight on a calm sea. The bright light of a waning gibbous beamed silver ribbons across the waves from the horizon to our ship. It was being chased by a deceptively small but unusually bright companion. Not quite large enough to burn with the nuclear fires of sun, but presently close enough to reflect ample light, this bright “star” was actually the planet Jupiter. Together, these two giants wandered peacefully across the sky, looking over us while another giant wandered beneath us.

If we look beneath the shimmering moonlight, beneath the waves that batter our ship, we find a system of currents as wide as the Atlantic Ocean (which happens to be about as wide as the Moon). The strongest lies at the surface and is known as The Gulf Stream. This mighty current wanders along the North American margin, carrying warm water from the tropics to colder northern latitudes. It is one of the primary reasons why London’s climate is milder than the more southerly New York City. It is also easy to see why this is the case: the sea surface temperature is 80°F today. This is in stark contrast to the frigid bottom-water temperature of 35°F. Clearly, the system of currents that runs through the deep is complicated. The speed, width, depth, and locations of these currents have been observed to vary seasonally. They surely have varied on much longer timescales as well. What is certain, however, is that they carry more than water and heat. Like rivers running through the landscape, currents carry the physical, chemical, and biological fingerprints of their source waters. That is why we chose to study this site. Particle transport associated with ocean currents needs to be untangled before we can understand how our planet works. In addition to radiocarbon, we are measuring the concentrations and isotope ratios of dissolved Oxygen, noble gases, Radium, Thorium, Protactinium, Neodymium, and dissolved lignin—tracers that allow us to compare the abundance of material transported horizontally by various currents to that raining down from above.

Today we leave Line W and move south toward Cape Hatteras for our third and final transect. With a little help from the wanderers below and illumination from the wanderers above, we will continue to read the message bottles of Earth.

Message in a bottle

Station 12 (i.e., "W")

04:15 EST

39° 3.409' N, 69° 22.632' W

winds: 4 knots

seas: calm

Ship time moves quickly. We finished our transect along the Nova Scotia margin, steamed through Igor’s wake (see picture at left), and have completed half of our stations on our present transect. We are currently on Station “W”, positioned at the intersection of the 3000 m isobath and a straight line (“Line W”) connecting Woods Hole to Bermuda. This will be our highest priority station because it has been continually observed since 2004 and provides a nice record of temporal variability in the NW Atlantic margin. And that is why we are here. To paraphrase the Cruise Planning Synopsis, our goal is to better understand the movement of organic particles (i.e., particles that are mostly carbon, like finely ground dirt or the soft tissues of our bodies) in the Northwest Atlantic margin. The implications of this work are surprisingly far reaching. It should improve our understanding of sedimentation processes, the formation of energy-rich deposits, the interpretation of sediment cores, the origins of organic material found just off of our coast, and the global carbon cycle in general just to name a few. How can we trace so many pathways? Consider the following.

Imagine you walk to the shore for the first time and look out to the sea. It is only natural to start asking big questions with small words. “Where did this water come from?” Not so very long ago people tried to figure this out by throwing corked bottles into the ocean. A letter inside would inform lucky beachcombers on distant shores of the bottles’ origins, with instructions for returning them. In this way, the bottles’ paths could be traced and currents could be mapped. Similar work is still carried out today. Check out Curtis Ebbesmeyer’s book, “Flotsametrics and the Floating World,” to learn how yellow rubber ducks helped map the Pacific. More sophisticated means of tracing the ocean can be found in NOAA’s incredible ARGO array of drifters (Coincidentally, one of our cruise participants, Larry George of WHOI, builds ARGO floats and will be repairing a spray glider recovered during our last transect).

But how, exactly, can we infer the history of organic particles sinking through the ocean? Fortunately, nature has been sending-off the particles with tiny corked bottles of their own: the atoms, isotopes, and molecules of which they are composed. By quantifying these constituents, we are able to constrain their histories. For example, my project will use radiocarbon (¹⁴C) measurements to trace the history of organic molecules dissolved in seawater (collectively called dissolved organic matter, or DOM). Since radiocarbon is an isotope of carbon that falls apart at a predictable rate (5,730 year half-life), we can infer that radiocarbon-rich molecules are fairly new while radiocarbon-depleted molecules are likely older. In this way, it has been shown that organic molecules dissolved in the deep ocean are 4,000 to 6,000 years old on average! In addition to tracing time, radiocarbon can be used to trace source material. If, for example, a particle sinks noticeably faster than its radiocarbon content would suggest, we might infer that older organic material was incorporated along the way. With a little more evidence, we might even be able to figure out where that material came from, how it got there, and more importantly, what it means in a broader context.

Check out the following resources for more information:

• WHOI’s National Ocean Sciences Accelerator Mass Spectrometer (NOSAMS) Facility

• links from the Radiocarbon journal homepage

• Willard Libby’s classic book, “Radiocabon Dating”

• Edgar Allen Poe’s short story, “MS. in a Bottle”

• ask me a question…

An uninvited guest

Station 8
42° 23.995' N, 59° 19.113' W
12:30h
Winds: 11 knots

Our final CTD for Station 8 is now on deck and we are ready to move on. Rather than moving further out into the Atlantic, we are going west. Where, exactly, is yet to be determined.

Like all research cruises, we came here with a detailed sample plan. It included estimates of where we would be, when we would be there, and how long each event would last before moving on to the next station. In our case, that adds up to 26 stations in 26 days under the assumption of 100% successful deployments and no weather delays. While we have had tremendous success so far, we are also aware of an uninvited guest in the Atlantic. His name is Igor, and he is on the move.

Hurricanes are one of our atmosphere's biggest shows. This one is several hundred miles across, but concentrated over a much smaller area. That means we can avoid the full fury, but we cannot avoid the waves. We have already entered into 10 foot swell and it is expected to grow. Fortunately, the dominant wave period (the time required for a full wave to pass by) today is long, approximately 14 seconds, and produces a fairly gentle roll. But it won’t last. And if it gets too rough, we might not be able to work on deck. We will have a meeting at 1300h today to determine, among other things, whether to steam to our next intended station or to circumvent Igor's influence and work through our remaining stations in reverse order. Regardless of our choice, we need to lash down our gear before moving forward.

For more information on the conditions at sea, check out data from the National Oceanic and Atmospheric Administration (NOAA) buoy array. For more information on Hurricane Igor, check out Wunderground.