After landing, a hole is drilled through the ice, and the sampling system is lowered through the hole to a depth of about 700 meters. The sampling system (the thin hole rosette) which was designed and built at the Lamont-Doherty Instrument Lab, allows the LDEO field team to examine the water as the assembly descends and to collect water samples for later analysis when interesting properties are observed. This work is supported by the US National Science Foundation.
This video was shot by Switchyard team member Dan Greenspan, who is a researcher at the Applied Physics Laboratory at Johns Hopkins University. Check out his blog, and his recent entry: “Traveling to the North Pole, Part 10: Eclipse, with Wolves.”
Time is flying, bringing us to our final days in Alert. We were able to recover samples from 12 stations, which is a great success and the second most successful year on record. Thanks to everyone who made it happen: Dale, Richard and Dan who went out every possible day to collect samples; Al and Jim for their support in Alert and of course our friendly Canadian colleagues..
The next two days are filled with packing and arranging the equipment and samples for their long journey home to New York. We plan to fly out of Alert on May 22 to Kangerlussuaq, Greenland but don’t know yet when the Air National Guard will pick us for the flight to New York. We hope to be home by May 25.
We have been steaming and searching for locations on the seafloor where the sediments are accumulating undisturbed. We tried without luck to take cores at several promising locations, however the cores came up less than perfect. It turns out that much of the undersea portion of the Line Islands has ocean currents that remove and erode sediment. This erosion shows up in the sediment cores as sandy layers where the very small grains of sediment have been swept away. So, we kept up our vigil in the main lab area, closely monitoring the seafloor for small pockets of sediment that looked promising. Some pockets are only a few tenths of a mile across while others are a mile or two. Many that look beautiful from a distance turn out to be ugly on closer inspection.
On our 13th core attempt of the cruise, we got lucky. The corer came back full of the beautiful, white mud. The 20-foot core contains over 250,000 years of sediment and spans the last three glacial cycles in earth’s history. During each of these cycles the earth cooled and large ice sheets expanded over North America and elsewhere. In our core, these cycles are indicated by color changes from greenish brown to white and back.
After lucky 13, we began to hone our strategy and are finding more locations with good sediments. We now have lucky 15, 17, and many more; we now have over 30 cores and counting. Not all of them are perfect, but we are getting better at finding good sediments and faster at coring them.
Alert hosted the first northernmost cancer-fighting fundraising event “Relay for Life,” an event sponsored by the Canadian Cancer Society to celebrate cancer survivors, remember loved ones lost to cancer and fight back against all cancers.
The 12-hour-walk was organized by Kristy Doyle, who lost her grandfather to cancer in 2010. Participants raised a whopping $7,580 and collectively walked 900 kilometers. I admit that I feel proud for doing my small part by walking 8 kilometers.
By Lee Dortzbach,
I work as the Chief Mate aboard the Research Vessel Marcus G. Langseth for this cruise and stand the 4 to 8 watch. Every morning as I get the ship where the scientists need to be, I watch for the sun to rise. Every evening I watch for it to set. There are some days when clouds are around and make for some great sunsets. Other days we cannot see the sun through all the clouds.
Sunday night after successfully recovering a gravity core about 42 miles north of the equator, conditions were right for a rare treat – the green flash. There were clear skies around the Sun, good visibility and a clear horizon. When I first heard about the green flash, I thought it was something that was noticeable and quick. Over the last decade, I have seen that it is not a sky-covering flash (as depicted in the recent Pirates of the Caribbean: At World’s End), but a short lived change of the sun’s light as it sets.
It happens because of refraction of light through the Earth’s atmosphere. The white light of the sun is broken into different wavelengths of visible light we recognize as different colors. The red and orange cover most of the sky, the yellow of the sun gets more orange-like as the sun sets and the blue and violet get scattered too much for us to see.
So what about the green? It too is scattered most of the time until the tip of the Sun is barely visible above the horizon. The Sun’s yellow light is refracted more and so the ‘yellow’ sun sets below the horizon before the ‘green’ sun. The sliver of green becomes visible to our eyes only when the bright yellow light is fading during the sunset. It starts from the bottom up in a horizontal band that grows a little taller as the sun sets. On a few occasions I have seen a sliver of blue/violet light below the green (a challenge against a blue ocean and a greater treat). In the latitude of the United States, it lasts about 0.7 seconds. Sometimes it can last up to 4 seconds. Ours lasted between 1 and 2 seconds. Definitely a flash compared to the core we just recovered!
For more information and other pictures of green flashes, click here.
Lee Dortzbach graduated from the U.S. Merchant Marine Academy with a B.S. in Marine Transportation in 2000. He has been around the world on several different ships over the last decade, including two oceanographic research vessels. He lives in landlocked Utah.
Yesterday we left our first study region with new samples from the seafloor and a healthy respect for the ocean currents that can erode sediment deep in the ocean. The samples will be useful for our research but we had to work for them. The seafloor we surveyed was heavily eroded and we had to look carefully before finding sites that were promising enough to sample. Even then we ran into difficulties getting the sediments back to the ship.
We spent several days surveying the seafloor using instruments on the ship to identify possible sites for sampling. We looked for flat areas where we could see layers of sediment below the seafloor. These layers show up in the echoes from sound pulses in a type of measurement called seismic reflection (see previous blog post). Unfortunately much of the region we surveyed has deep gullies with no sediment layers. Ocean currents have scoured these regions leaving no sediment for us to core. We finally located several small areas that had a hint of sediments and one big pile of sediment we thought would be our best chance for samples.
We use a sediment corer to take samples of the seafloor. The corer is a long tube with heavy weights on top that push the tube down into the seafloor. When the tube is pulled out it removes a long cylinder of sediment that we bring back to the surface. The corer is lowered on a steel cable at about 1.5 miles per hour and takes more than an hour to reach the seafloor. At 150 feet above the seafloor, a mechanical trigger releases the corer from the cable and 5,000 pounds of steel rocket towards the bottom. The weight and speed push the corer up to 30 feet into the sediments. Then we have to pull the corer back out. Sometimes this is easy but if the sediments stick to the corer it can take almost 20,000 pounds of pull to free the tube and slide it out.
The other important step in coring is to keep the sediments inside the tube on their two-mile trip back to the surface. This seems obvious but we ran into troubles with the very first core we took. Usually a ring of metal fingers in the bottom of the core (called a core catcher) keeps the sediment inside the tube. However, the sediment we were coring contained a lot of sand-sized shells that was washing out of the tube leaving us with no sediment by the time the corer reached the surface. To prevent this, we added a sock of fabric around the core catcher to keep the sand from washing out. Bingo! The fabric kept the sand in the corer and we started recovering sediments to study.
When the sediment corer arrives at the ocean surface it is laid horizontally along the ship’s rail where we take a sample of the sediment in the core catcher to determine the age of the bottom of the core. This age is determined by looking for a striking, pink colored shell made by a type of plankton called foraminifera. This pink foraminifera was abundant in the Pacific Ocean until 120,000 years ago, so if we find pink shells we know the sediments are at least 120,000 years old. We will do more detailed analyses later but this age gives us our first peek at how much time it took for the sediments to accumulate.
Next, we cut the core into smaller sections that are easier to handle and the core is split open so we can see how the sediment looks. We study its color, texture and composition before storing it in a refrigerated container aboard the ship. At the end of the cruise we will send the container to the Deep-Sea Core Repository at Lamont-Doherty Earth Observatory where the sediments will be preserved for researchers around the world to study.
We are now steaming south to the equator to start a new survey to find the right locations to drill more sediment cores.
Finally, we arrive at the Canadian Forces Station (CFS) Alert around noon. Our home for the next few weeks.
We are in the fifth day of our research cruise to the Line Islands and shipboard life is beginning to settle into a routine. Most people have their ‘sea legs’ and our sleep schedules are adjusting to the midnight to noon or noon to midnight work shifts. Meals are a time to catch up with scientist and crew, and the motivated scientists have begun regular exercise schedules in the ship’s gym.
As we steam over the incredibly wide expanse of the Pacific Ocean, the waves seem endless and monotonous, and the wind blows steadily from the same direction for days on end. However, beneath us the seafloor is far from monotonous. Huge mountains rise 10,000 feet above the seafloor and create escarpments, ridges and valleys that would rival the peaks of the Rocky Mountains. It is along these mountains that we hope to find sediment for our research.
Using scientific instruments we peer ‘through the looking glass’ to learn what the seafloor and sediments look like. The analogy to the looking glass is apt: Alice stepped through the mirror to see the world beyond and we peer through the bottom of the ocean to see what is below. However, unlike Alice, we use our ears. Short pulses of sound from the ship are focused on the seafloor and we listen to the echo and reverberations that return to the ship. Depending upon the pitch and intensity of the sound we can look at the top layer of the sediment or much deeper.
The most basic echo we listen to comes from the very top of the sediments. This echo travels down through ocean, bounces off the top of the sediments and returns back to the ship. We measure the time it takes to go down and come back up, and knowing how fast sound travels through seawater (~one mile per second or 3,400 miles per hour!) we can determine the distance to the bottom of the ocean. The times are very short, about two seconds for water a mile deep. We use these distances to construct a detailed map of the bottom of the ocean. This map shows the mountains and valleys on the seafloor where we will take our sediment samples. We also listen to how loud the echo is when it comes back to the ship. Hard surfaces like rock have a loud echo while soft sediment gives a quiet echo. This is an additional way to determine where there are ocean sediments to sample.
If we turn up the sound volume and use a lower pitch we can look beyond the seafloor into the sediments below. Now rather than just one echo from the seafloor, we begin to hear many echos as sound reflects off the different layers in the sediments. These echos allow us peer beneath the seafloor to know how thick the sediment is and whether it is nicely layered or jumbled and distorted.
When we find the right sediments—not too deep, smooth, with nice layers—we will take cores of the sediment to study the climate history preserved in the layers.
Arctic summer sea ice is declining rapidly: a trend with enormous implications for global weather and climate. Now in its eighth year, the multi-year Arctic Switchyard project is tracking the Arctic seascape to distinguish the effects of natural climate variability from human-induced climate change. The University of Washington is leading the project.
- A) The Canadian Forces Station, Alert
We will fly from the Canadian military base at Alert, Ellesmere Island, land on the ice by ski plane to drill holes, deploy instruments and retrieve water samples. We will measure water temperature, salt content and levels of dissolved oxygen, and a wide variety of natural and man-made substances. Our goal is to understand how much fresh water is entering the system, where it is coming from (sea ice melt, river run-off and so on) and where it exits the arctic, altering currents in the North Atlantic Ocean.
During the next few weeks we will blog from the field; Follow our work on the Arctic Switchyard project page.
It is the middle of the night and I am wide awake thinking about the ocean, specifically the bottom of the ocean. Is it rocky? Jumbled? Smooth? I am wondering this because I want to take samples of the seafloor to study. Rocky is bad. Jumbled is bad. Smooth is good.
In one of my favorite New Yorker cartoons a woman says, “I don’t know why I don’t care about the bottom of the ocean, but I don’t.” Well, for the next four weeks our research group will care a lot about the bottom of the ocean. We are sailing to the middle of the Pacific Ocean where we hope to collect sediment to study how climate has changed in the past. Our destination is a group of atolls and seamounts collectively known as the Line Islands. They include Kingman Reef (U.S.A.), Palmyra Atoll (U.S.A.) and part of the island nation of Kiribati.
The ocean around the Line Islands is over two and a half miles deep (4 km)—too deep to preserve the climate changes we want to study. So, we are going to take sediment cores on the flanks of the islands where the sediments are better preserved. The flanks are also where a lot can happen to the sediments. Slumps can break off huge chunks of sediment, ocean currents can erode the sediment and slumps from higher up the flank can deposit thick layers of sediment. All of these happenings alter or erase the regular ordering of the sediment (the stratigraphy in geologists terms) and make them unusable for our research. So, I am thinking about the bottom of the ocean.
Our group is sailing on the research vessel (R/V) Marcus G. Langseth, an oceanographic research vessel operated by Lamont-Doherty Earth Observatory (where I work). The ship is a floating scientific laboratory, with the ability to study and take samples of the ocean water and sediments wherever we go. The scientists on board include seventeen researchers from nine institutions. In addition, there are 34 technicians and sailors who make sure the ship and scientific instruments are functioning properly so we can collect the data we need. The moment we leave the dock in Hawaii will be the culmination of almost a year of planning, a lot of hard work by the crew of the Langseth, and financial support from the U.S. National Science Foundation.
Our goal for this cruise is to collect cores of deep ocean sediment that we can use to study the past behavior of El Niño as well as the climate of the tropical Pacific Ocean. Although our studies focus on the Pacific Ocean, the results could tell us about many different areas of the globe. El Niño weather affects regions as far apart as Indonesia and New York State. In fact, El Niño events are responsible for the largest year-to-year changes in global weather. Our goal is to learn how El Niño has varied in the past so that we can develop better forecasts for the future of El Niño into the 21st century and beyond.
Over the next four weeks I will be writing a series of articles about our cruise. Topics will include El Niño, life aboard the ship and how we actually collect water and sediment samples from the ocean. Stay tuned!
In the meantime you can track where we are online.