ANT-XXVI/2, Weekly Reports 3+4+5
12 December 2009 – 1 January 2010
Half of the expedition ANT-XXVI/2 is almost over already. We are now in the western South Pacific and will steam to our southernmost study location at 69 degrees South in the coming few days. In this region we expect to find the sea ice edge, which is currently moving slowly to the south. In the past three weeks, we’ve played hide and seek with nearly unpredictable weather, tried to understand the distribution of sediments in the Pacific sector of the Southern Ocean, and of course we celebrated Christmas and New Year’s Eve.
Three weeks ago, we managed to avoid bad weather conditions for the first time by taking a detour to south of 60°S, where we conducted a ‘pre-site survey’ for the Deep Sea Drilling Project. While doing this we had to follow regulations outlined by the Umweltbundesamt (Germany’s Environmental Protection Agency) governing protection of whales within the area of the Antarctic Treaty (south of 60°S). The planned seismic survey had to be done during the day to ensure that whales could be observed, and the seismic work interrupted should a whale approach the ship. Whale watching had to be conducted by two additional people on the bridge as well as by helicopter. All participating scientists received special instructions, watch plans were worked out, and a helicopter prepared for a flight.
To complete the seismic survey, a 600-m-long seismic streamer was deployed into the water at the stern of the ship. This is a plastic hose with hydrophones that is towed behind the ship and receives the signals emitted by an air gun and reflected from the seafloor. The result is a kilometre deep acoustic screening of the seafloor, which provides information on sediment distribution and layering. Everything was ready, the weather conditions perfect, yet, the survey had to be cancelled: the recorder of the seismic system refused to work. In addition to unpredictable weather, technical failures like this also play a role on such expeditions, even though this can be very frustrating at times. On the positive side: we recovered a 23-m-long sediment core at the location proposed for drilling that documents the climate history of the past 200,000 years. To our surprise, the core contained frequent, finely layered (laminated) sediments that may be the result of oxygen depletion due to high organic matter supply to the seafloor, suggesting high biological productivity in the surface waters. This finding seems unusual in areas as far away from the coast as this.
On December 13th, we started to steam northward again, back to the area we had fled earlier. We wanted to continue our work at the East-Pacific Rise, and also try to conduct more seismic surveys. The total failure of the seismic recorder led the participating seismologist as well as the ship’s electricians to search the deepest parts of a container where several geophysical instruments are stored. After disassembling an old instrument they found components that allowed them to repair the broken seismic recorder. On December 14th we were able to successfully complete a seismic cross profile at a potential drilling location near the southeasterly part of the East-Pacific Rise. This revealed a 1000m-thick layer of sediments. On the ridge at water depths of 3000m, we again found calcium carbonate-rich sediments. They are made up of microscopically small tests of unicellular organisms (foraminifera) and algae that secrete calcareous plates (coccolithophores). Unfortunately, the multi-corer that we use to sample the surface sediments did not like this sediment type. The ~2m high multi-corer lands on spider-legs on the seafloor and, and using heavy lead weights, pushes 12 plastic tubes into the sediment. During careful heaving of the instrument, the tubes are automatically closed. This closing mechanism often fails in these carbonate-rich, sandy sediments, but high waves also make it difficult to carefully land the instrument on the seafloor.
Around December 15th, the weather conditions again forced us to leave our route and turn westward. Hence, the second attempt to sample potential drill sites further north had failed. But an alternate route and program was quickly found. We crossed one of the big fracture zones in the South Pacific. At the Eltanin-Tharp fracture zone, which stretches, crescent-shaped across the South Pacific, the ridge system is dislocated by ~800km. On a 400km wide ridge segment south of the fracture zone and north of the Udintsev fracture zone, we reached our originally planned route again, yet our sediment echosounder, the PARASOUND system, did not show any sediment deposits in this area. This was more than surprising and only changed as we reached the area of the Udintsev fracture zone, which is influenced by two oceanic fronts, the Subantarctic Front and the Polar Front.
These fronts mark the boundaries of west-east trending currents that are part of the Antarctic Circumpolar Current (ACC) system. The ACC is the largest current system on Earth and it is the only one that connects the water masses of the Atlantic, Pacific and Indian Oceans. The development of this enormous focal point of mixing and distribution of water masses in the global circulation system is critical for the evolution of the global climate. For the first time, we are collecting sediment material from the Pacific sector of the ACC that will allow us to reconstruct its geological history in the large area of the polar South Pacific. The goal is not only the reconstruction of its history, but also the documentation of climatically relevant linkages and exchanges between the polar South Pacific, the tropical and north polar latitudes during past cold and warm periods. These data will also contribute to global studies of past climate states, such as the EU project ‘Past4Future’, which started on January 1st, 2010. More than 200 scientists from European countries will work together to reconstruct the climatic conditions of the current (last ~12,000 years) and penultimate (~110,000-125,000 years before present) warm period. The first few thousand years of these warm periods were warmer than the present climate and the sea level was up to 3-5m higher. The global data compilation and climate model simulations based on these data are expected to give insight into the mechanisms and impacts of such ‘warmer-than-present’ conditions. This will aid predictions of future climate developments under climate warming scenarios.
At the moment, a large poster with Christmas decorations is hanging by the stairway. Each day, more Christmas and New Year’s greetings are pinned to the poster, sent by ministries, city majors, research vessels, research stations, scientists and friends from all over the world. People are thinking of us these days before Christmas, when we will have changed our course towards the southwest, towards the Amundsen and Ross Seas. We want to map two large seamounts that are shown on our maps between 64° and 65°S. The water and air temperatures are decreasing continuously towards zero degrees, it is snowing occasionally, and icebergs are keeping us company.
On December 24th, work was reduced to a bare minimum starting at 3pm. Presents were made and wrapped, and a reception was held in the “Blue Salon” on the B-deck. Everyone was dressed up. The ladies, who are usually wearing jeans and T-shirts or cold-weather gear, wore dresses or nice pants and even put on make up. The male participants at least put on clean pants and shirts. The officers turned up in uniform, showing golden buttons and stripes. Two short speeches by the captain and the chief-scientist were followed by a glass of mulled wine. All this was done in front of one of the three Christmas trees that were put up and decorated in the “Blue Salon” and the messes on the C and D decks. (They survived the long journey from Germany in the fridge at 4°C). The only things that were missing on the ship were real candles. For security reasons, they are strictly prohibited. For dinner we had bockwurst and potato salad, a tradition in many German households (the chef needs some time off too!), and there was a party in the evening.
On December 25th, following an extended lunch with goose and red cabbage, our scientific work started again. (Ship time is not cheap!) Mapping of the seamounts over Christmas actually showed that there are no seamounts. We still know less about the surface of the Earth than about that of the moon or Mars! The subsequent cruise track crossed the Pacific-Antarctic Ridge and headed towards the Subantarctic Front, making yet another saw-tooth in our cruise track towards the west. This segment between 64°S and 54°S with a distance 700 nautical miles (=1200km) should be completed by New Year.
We were supposed to celebrate the transition into the new decade at the Subantarctic Front. On the way north, seven stations with piston core, multi-corer and CTD were successfully completed. The shallowest station was on the ridge at 2824m water depth, where we expected to find carbonate-rich sediments again. First the multi-corer was deployed and recovered 10 sediment-filled tubes, but when the piston core came back to the surface, there was a big surprise – the entire 15 metres of tubing were gone! We still don’t know how this was possible, as all connections between the tubes and the weight were checked prior to deployment. Only the so-called trigger-corer that triggers the piston core above the seafloor, recovered a 90-cm-long core. The subsequent stations were, however, successful and recovered 15-21m-long sediment cores that document the climate history of the past 300,000-600,000 years. Just in time for New Year, we reached the Subantarctic Front. The onboard meteorologist had predicted good weather conditions for New Year’s Eve, and preparations for a short break and a party started, but the weather changed suddenly. Within a short time a harmless low-pressure system developed into a big storm that moved towards us at speed of 40km/h. The weather window for station work had suddenly shortened to New Year’s Eve and the following morning. We had to decide: party or samples. The captain and chief-scientist suggested a compromise: continuation of sampling, but the traditional reception on the bridge at midnight and party on December 32nd. Not everyone was happy, but who else has had the chance to celebrate New Year’s Eve in Antarctic waters on December 32nd? Only us!
In the name of all participants, best wishes for 2010 and the coming new decade!
(Chief Scientist ANT-XXVI/2)
PS: I have to apologize at this point for the delayed delivery of the weekly reports. The reason for this is that I’ve been suffering from a slipped disc since before Christmas, which has restricted my movements considerably. I was not able to sit, and any writing in bed was torture. Most decisions regarding the expedition were done from my bedroom. My condition is improving now and I am therefore trying to catch up on writing.