Off in deep water with ice-rafted debris

We are approaching the end of the drilling operations. We need to leave here four days from now to make it to Hobart on time. We are drilling in the distal end of a fan now in nearly 4000 m water depth and find laminated silts and clays and occasional rock clasts. These rock clasts are most likely ice-rafted debris, rock eroded by glaciers, that then calved and produced icebergs. The debris then gets carried off-shore by icebergs, which melt and release the rock debris so that it can fall to the sea floor. For a decent recent calving event see for example this website from NASA. It shows a series of images documenting the recent calving of the Mertz Glacier Tongue near to where we are drilling. You may have heard about it on the news, it is going on right now.

However, not all icebergs in this area originate at the Wilkes Land coast. Here in this core section is a piece of volcanic rock that may have come from the Ross Sea. I was there two years ago with the Antarctic Geological Drilling program (ANDRILL). There are several volcanic islands there that are composed of volcanic rocks like this one. (See the posts on this blog from 15-16 Oct. 2007.) A glacier may have eroded it there and icebergs may have carried it out here.

Happy down-hole loggers

This is Annick, one of the two down-hole loggers. Here she was getting ready to start her work. The down-hole loggers were very happy the last couple of days, because they finally had a chance to collect some data. Poor drillhole conditions and bad weather did not make it possible to log any previous boreholes. The down-hole logging is very important for our studies. It is the only way to collect an almost continous record of the formations in the subsurface. During drilling there are always core breaks or sections that are not recovered, e.g. because the beds in the subsurface have too many large stones in them, or because the material is too soft or too loose. The down-hole logging provides a means to collect data on these missed sections. The loggers use several sets of tool, or instruments that are lowered into the borehole. One of them is the formation microscanner (FMS), which provides an image of the borehole wall. You can even see rock clasts in the borehole wall with this. Another tool is the gamma-ray tool. This tool is able to detect potassium-bearing minerals by exciting the potassium atoms with a radioactive source. In many cases the potassium-bearing phases are clay minerals, so it can be used to pick up fine-grained beds that were missed when coring. Other tools measure the resistivity of beds by sending a current trough the formation. Sands usually have high resistivity, so it is very useful to pick up coarse-grained beds. You can see some of the tools in the box on the photo to the right. These tools are lowered into the borehole on a wire, after the hole has been prepared for logging.

Last bit of core through the lab?

Today was like many days on the cruise. Core was coming up and we were processing it through the lab. In the afternoon we stopped drilling and the hole was prepared for down-hole logging. More on that tomorrow. This may have been the last bit of core that we describe on our shift, so it is a good time to explain what goes on with these cores before we get them on the table. Here you can see Erik and John splitting a core for us. The core is hard, like rock, so they use a rock saw to cut it into two equal halves. One half is the Archive half: we get to describe that one and it is kept in pristine condition as much as possible. The other half is the Working half: that half gets sampled, so small pieces are cut out for laboratory analyses. After the split, we describe the features visible on the cut face of the Archive half. Today most of the rocks were laminated and some had nice microfaults (see photo). After core description the cores are photographed using a line-scan imager and fed through a logging track for measurements of color reflectance and magnetic susceptibility. After we have finished the measurements the section halves are wrapped in cling wrap and then fed into a D-tube for storage. Here you can see the D-tubes: those with the red caps are for Archive halves and those with the black caps for the Working halves.

LIVE from Antarctica

We are drilling in deep water again, off-shore Antarctica. We were unable to reach our coastal site, but we are getting great core from where we are right now. We are now drilling back into the Late Miocene and I hope we are going to reach the Middle Miocene climatic optimum. This is a time when the Earth was slightly warmer than today and it may give us a window into understanding what is up for the future. Let's hope we can get that far.. We are currently at a depth of more than 400 mbsf and we are still drilling.

Another crossing of the Antarctic Circle

For the past days we have done our best to reach the drillsites 9B and 8A near the coastline (see ice image in previous post). We did drill there for a while with great success before the storm, but after the storm the ice had shifted and we were not able to get back into the area. There are too many icebergs and pieces of multi-year sea ice. We did see some more of the coast of Antarctica and more penguins, Adelie penguins this time, on icebergs. The penguins have big bellies and look very well fed at the end of the summer. They are ready to face winter, which you can tell, is now coming soon.

The break in drilling gave us a chance to catch up with report writing, and in the chemistry lab almost all samples are processed now. For you science nerds (like me) out there see this video made by chemist Tina about how high precision balances work on a ship:
If you are interested in what else goes on in the chemistry lab, watch this video, made by Dan Brinkhuis, the shipboard videographer:

Storm breaks off large piece of an ice tongue in our research area

We had very stormy weather over the past three days. The waves were up to 25 feet (8 m). For some reason the motion of the ship was very irregular and we were rolling around in our beds and not sleeping very much. Today the storm had died down and we tried to get back to our site near the coast, but poor visibility because of snow and the ice conditions made us turn back. The storm has broken some icebergs into numerous small pieces and has shifted some larger ones around. We also received a warning from the Naval Ice Center that a large piece of the Mertz Ice Tongue near our drill site has broken off, presumably due to the storm. You can see the crack in the image. The piece of ice that broke off has now been labeled as iceberg C-28, with a size of 43 by 18 nautical miles (80 x 33 km): try to imagine how big that is!

Tomorrow we are trying to get back to our drill site 9B between the icebergs again. Let's hope we can make it!

Penguins!

When I got up this morning there were penguins on the icebergs. I saw four of them on a tiny piece of ice. They were black and white and very small, probably chinstrap penguins. I didn't have my camera with me, but Stephanie saw some as well and took a picture. Here it is. These penguins like to hang out on icebergs during the summer. You can find more information about the chinstrap penguin here.

Icebergs at night

First of all: Happy Chinese New Year! Our Chinese colleagues here on board are celebrating a year of the Tiger. It is also Valentine's Day, and some others were scrambling to have flowers sent remotely. It is fabulous to experience the cultural diversity here on the ship.

It was a difficult night with decisions. We were getting great core and were advancing down through the formation to our drilling target, but two icebergs came closer and closer. The ship had its bow turned towards them and the bow lights were shining on them in the darkness. After waiting and hoping that the icebergs would make a turn away from the ship, we had to trip out of the drillhole and the ship had to be moved to get out of their way. Another problem is that a large storm with up to 65 knot winds will arrive here tomorrow, so we temporarily need to move away to the shelf edge to wait out the weather. We will have to return to this coastal site later. It is simply to dangerous to stay here in a storm amidst the icebergs.

Another challenge is that now that we get closer to March the hours of darkness are lengthening. On 21 March the day and the night will be of equal length (12 hours) around this area, near the Antarctic Circle, whereas there were 24 hours of daylight here in late December. In late June there will be 24 hours of darkness.

Between the icebergs

This afternoon we arrived at one of the shelf sites where we are going to drill for more Eocene: a time when it is believed there was no ice on Antarctica. On arrival we found that there is plenty of ice now. To reach the site we had to move around a cluster of icebergs. You could follow our curvy route on the monitors that are hanging around the ship that show the transit track. You can see the coastline of Antarctica as a white line below. I was in the galley eating my breakfast this morning when we went around a curve and the ship was leaning quite steeply. When we finally reached the site this afternoon, there was an iceberg sitting almost on top of it. We are now waiting for ice to move out of the way so we can drill. The icebergs were beautiful with nice blue ice. But: let's hope that they will be out of sight tomorrow when I wake up, so we can drill. It is getting colder already, now that autumn is setting in here. When we go outside we have to dress in warm clothes and even then the wind is very cold. We do not have much time left on the shelf before winter is setting in: the Antarctic summer is very short.

Triple core and back to Antarctica

We are in transit back tot he Antarctic coast to reach a site closer to the continent. We are navigating bergy waters so our route is curvy to get around these obstacles. We are still processing cores from the previous site, which was triple cored. Triple coring is sometimes done to fill gaps in the record caused by core breaks and cores that were not entirely recovered due to the heave associated with large waves. Filling these gaps allows for complete high-resolution climate records, and that is what we are after.

The weather hasn't been great lately with lots of rain and snow giving poor visibility. Nevertheless we did see some humpback whales, who were checking out the ship. They were so close that you could see the texture of the wet skin. The weather is reasonable now and I just got outside to watch us passing a huge tabular iceberg. My colleague Kota got sprayed by a wave, because we are still in rough waters. More later once we arrive at our next site, near Antarctica.

What's on the table today?

Core barrels are pulled up from more than 3000 m water depth and are filled with delicious green mud. It is busy in the smear slide corner, because the composition of these fine-grained sediments needs to be determined by microscope: the particles are too small to be seen with the naked eye or a hand lens. Kota Katsuki is the day shift smear slide King. On the night shift Masako Yamane is doing a great job (see photo with Kota and Masako). When a new core is split and is brought to the description table, Kota takes smears of the mud with tooth picks and smears the mud on a glass microscope slide. Under the microscope he can identify the different components and determine how many diatoms are in the sediment. Today we were seeing silty clays and diatom-bearing silty clays in different shades of green. There were were also nice laminations of silt.

Coring is going well, but we are pulling out of the hole to get some double cores to fill gaps. A weather window is opening up near the Antarctic coast over the weekend and we are going to move there tomorrow evening. This is our last chance to get close to Antarctica before autumn storms and developing ice prevent us from going there. We will most likely return to our present site later to finish coring further back in time. The frequent transits and pull-ups due to weather is taking a bit of a toll on the science team. This is also a difficult period in the cruise: it is still long before we return and it has been long enough that people miss their family and friends. We are also getting a bit tired. The nice core that we are getting, the new friends we are making here on board, and the science, however, is making all good!

Good old diamictite and another transit

The drilling started out very well yesterday, but unfortunately about 30 meters into the sea floor the drillstring broke off and it had to be left behind in the hole. It was then just time to move out of the shelf area, because of the approaching big storm. We did get diamictites with quite good recovery before the incident. There were big boulders in them that we drilled through as well. These diamictites likely originate from the erosional and grinding action of glaciers, which released their debris upon melting in the ocean, or by sedimentation from icebergs, which are plenty at this site along coastal Antarctica today. Notice the big pink granite clast: quite amazing to find that in a core!
After the drilling terminated the beacon was floated from the seafloor to the surface and was pulled in. We received an update on the plans for the next site in the core lab, as usual. Co-chief Carlota (seen on the back) here is explaining what is happening. We are in transit so often these days, that when you get up the first question is: where are we, and what is happening? We actually just arrived on our next site in just over 3000 m of water. The weather here is still not too bad, so we may get some coring done before the storm. In the mean time, so many good data sets have come out of some of our previous sites that we are having a science meeting tomorrow to discuss the implications.

Across the Antarctic Circle

Today, as I got up, we passed the Antarctic Circle in transit to the next drill site. We were all taking pictures and watching the ice. When we arrived at the innermost shelf site we were surrounded by so many icebergs that it was too dangerous to stay. A whale came to check us out, but left quickly.

We moved to a site further out on the shelf so that we would have the opportunity to move away to the North out of the icy waters if visibility would deteriorate. From here we can still see the pack ice (sea ice) in the distance. It has gotten colder during the day. This evening it was the first time I put all my cold weather gear on with all the hats and gloves. Bad weather is coming in this evening: we will be hit by 60 knot winds and snow. It is very likely that drilling operations will have to be shut down, but for the moment we have the drillstring in the sea floor and are moving ahead. I just saw the first core coming up and it had mud with gravel in it. The second one is about to come up soon.

Seasonal algal blooms recorded in an Antarctic sediment core

For the past two days we have been working on collecting a very unique set of cores. We are currently coring into the Adelie Drift, in a small basin on the Antarctic shelf with a water depth of about 1000 m. The basin is filled with organic sediments composed of more than 90 % diatoms, other microscopic algae and zooplankton. That type of sediment is called diatom ooze. In the photo, you can see a part of a core that we processed today. Each light-colored layer represents the cysts left by a spring bloom of microscopic algae, predominantly diatoms. These diatoms bloom when daylight lengthens and when the sea ice starts to break up in the spring, so that nutrients are released into the surface waters. The dark layers in the core are created in the autumn and winter, when the days shorten, the sea freezes over, and eventually the polar night takes over. Besides diatoms, we also found fish bones in the dark layers in the cores, predominantly vertebrae. Each light and dark layer forms a couplet representing one year. Like tree rings, changes in the surface climate conditions affect the thickness and composition of each layer. The Adelie Drift probably contains about 10,000 of these laminae (layers) going back 10,000 years. This is a very valuable record documenting short-term climate change in a very remote place on our planet.

The coring of these sediments is a bit different from the drilling we were doing at the previous site. We are using an APC piston coring system now (see drilling equipment class in an earlier post). It works like a giant syringe where watery mud is extracted out of the sea floor. The first couple of cores were very soupy and accompanied by a very powerful smell of rotten eggs (H2S). We also had some issues with exploding cores from all the gases that were released out of the sediment: there is a huge pressure difference between atmospheric pressure here on deck and the weight of 1000 m of water pressing on the sediment there below. Here is a photo of what is left of a core liner after the core exploded. Luckily no one got hurt, because everyone is wearing protective safety gear.

We were treated with another beautiful day today as well. It is almost unreal: we are in Antarctica and it is supposed to be very cold and windy, but it was just around freezing and in the sun it felt quite pleasant. We did feel the catabatic wind come down from the ice-sheet when the sun was setting, but it wasn't too bad at all. The catabatic wind, is a typical wind of the polar regions, and it develops when air cools over the surface of an ice sheet, becomes dense, and flows out to the coast. The sun is setting at around 11 PM. It does not get completely dark because the sun is only a few degrees below the horizon and the sunset becomes a sunrise within 2 hours. In the photo below the surface above the iceberg is the top of the ice sheet. It is odd to see the sun set above an ice sheet, but it is a magnificent experience!

Whales, the sun, core, and a view on the Adelie Coast, Antarctica

Today was a perfect day. When I got up this morning there was no wind, the sun was out, whales were checking out the ship, and we had a view on the coast of Antarctica. That is a lot! A few hours later the first cores came on deck. You can imagine that the whole science team was in a very good mood. The Adelie Coast is one of the windiest places on Earth. The area is usually very foggy with low visibility. None of that seemed true this morning. We were all relaxing a bit before the first cores came up: enjoying the views with the numerous icebergs.
Most icebergs are grounded on the shelf, but a few smaller ones were on the move. We are actually moving out of the way of one now. This evening a few cores were split, and we got to describe them. I will show you some more of that tomorrow. Our internet is going to be down in a few moments. Enjoy the view on the Adelie Coast below. The white above the horizon is the East Antarctic ice sheet, not a cloud. Talk to you later!

In transit to the Adelie coast

We are in transit to the Adelie coast, where our next drill site is located. Unfortunately, bad weather and poor hole conditions prevented down-hole logging at our previous site: I will explain what that is later. In transit to the Adelie coast we expected to encounter icebergs. This afternoon the ship passed a large tabular iceberg. It was first spotted on the radar. Diego, the ice observer then got onto his post (see photo). These large icebergs may calve and produce small ones that are not visible on the radar. They are called growlers and Diego is very good at spotting them. His job is to advise the Captain and first mate so that the ship does not run into them. Visibility was very good this afternoon, so we were doing more than 10 knots despite the ice.

Later John, the first mate came out and measured the dimensions of the iceberg with a sextant (see photo left). It turned out to be about 3000 feet (1000 m) long: you wouldn't say that, huh? Later that night when I came off shift I had the opportunity to watch the sunset. In the photo, the sun has already set, but it is just below the horizon. In a way it is a sunset and sunrise in one: during this time of the year that is as dark as it gets. Although it got quite cold (1-2 degrees C) a bunch of us were enjoying this view. You can see the people near the bridge to the left, and the dark bump on the horizon is another iceberg. We could see small bits of ice near the ship as well.

I am already excited about tomorrow, when we will arrive on the Adelie coast, only 18 miles from the Antarctic continent. There will be a lot of ice, but hopefully not too much, so we can get some more cores, this time spanning the past ca. 10,000 years.

In the Eocene at 1000 meters below sea floor

We made it! After 1000 meters of drilling the microfossils indicate we are in the Eocene (more than 34 million years ago). Today the last bit of core was split and in the photo you can see the finger pointing at the piece that came from exactly 1000 meters below the seafloor. From the core we can tell that the sediment, which is very fine-grained clay, had been deposited quite gently particle by particle. It became a rock when cement had precipitated in the pores. Numerous burrows in the claystone tell us that the sea floor was once a lively place. The types of burrows, and the microfossils, tell us it was likely a deep marine environment, and that it was a greenhouse world. How much warmer it was here so close to Antarctica and how it got so cold as it is today is what we need to find out next through analyzing samples. Most of this work will be done when we get home. But the important part is done: get the rocks of the right age.

But it is not time to go home yet! Instead over the next few days we will move closer to Antarctica. The ice conditions have improved and one of the shelf drill sites on the Wilkes Land coast is free of ice. Now the drillers are pulling up all the drillpipe. We are in more than 4000 m of water, so that is 4000+1000=5000 m (15,000 ft) of pipe that is currently hanging below the ship, imagine that! The pipe is only several inches across, so it behaves like a string of cooked spaghetti. We are currently having high seas with waves up to 20ft (6m), so it is a real challenge for the drillers to pull it in.

I am really excited to wake up tomorrow and perhaps to see the icebergs and the sea ice. We may have to move slowly though because of the bad weather. After this one that we are currently in, a second storm is predicted to hit us. We have had snow today as well, and due to the strong wind and high seas it wasn't pleasant outside. Let's hope it will improve soon.