The multi-net ladies after successful deployment of the device (photo: S. Fietz)
ANT-XXVI/2, Weekly Report No. 7
10 January 2010 – 17 January 2010
On January 10th, we left our southernmost station and steamed north towards Wellington, New Zealand. Only another 15 days before we would again lay eyes on land. The shipment of expedition goods and samples is being organized via email with the ship’s agent in Wellington. Very colourful immigration documents have to be filled out by everyone. We are told that the ship will go alongside the Aotea Quay in the container harbour. Everything we will take off the ship will be carefully checked. Does someone have hiking boots with soil or even worse, seeds from a different continent on the soles? Has anyone touched a living chicken in the past 30 days? The import of food is strictly regulated and mostly prohibited. Food for the time in the harbour has been ordered through the agent, because all food on the Polarstern has to be locked away and sealed.
Only two weeks for the completion of the cruise report, where all scientific activities will be documented and explained. We have a detailed plan regarding who will write about what and which tables and maps will be necessary. Everything will be compiled and decisions will be made as to how the different working groups can collaborate. Where are connections, how can the expertise at hand be combined and documented concisely? After the combined efforts during the expedition, when we worked 24 hours in shifts, we don’t want to leave the ship without decisions on future collaboration based on the motto trust, cooperation, multi-disciplinary, reliability.
Sunset (photo: Young Nam Kim)
But before we leave the ship on January 26th, we have another 1700 mile transect ahead of us, along which we want to sample sediments and water masses starting in the area of winter sea ice cover all the way to the subtropics. Furthermore, we want to do further pre-site surveys for the ocean drilling program at four locations. In the iceberg zone that is covered by sea ice in winter, sediments are deposited at very low rates. The 10-17-m-long sediment cores that we recovered from the area south of the Pacific-Antarctic Ridge therefore cover a long time period, some of them more than 4 million years i.e., back to the so-called Pliocene. This is a time with higher greenhouse gas concentrations than today. There was no ice in Greenland like today, and the Antarctic ice sheets were also smaller. The sea level was up to 25 m higher than today and the global climate significantly more uniform. We can study this interesting time period, which can be seen as an analog for future warmer climate states, using these sediment cores.
On our way north we are again deploying the CTD with rosette to measure the physical properties and biological production, and to sample the water column. Additionally, we are using the multi-net to collect microscopically small plankton in the upper 1000m of the water column. This device consists of 5 nets that are moved vertically through the water and are opened and closed at different water depths, allowing the sampling of micro-plankton from different depth ranges. We are mainly interested in micro-plankton that secretes siliceous or calcareous skeletons or tests that are preserved in the sediments as indicators for past environmental conditions. We want to learn more about their habitat and hence the environmental signal that their occurrence in the sediments represents.
The ‚black‘ iceberg (photo: Young Nam Kim)
In the south it doesn’t dark at night. On some days we see a colourful sunset framed by icebergs that is followed after only two hours by an even more spectacular sunrise. Although we won’t conduct any more seismic surveys on our last transect, they are planned for the following cruise, we still have to follow the strict regulations of the German Umweltbundesamt (Environmental Protection Agency) for the protection of whales south of 60°S. At all sampling stations at least one scientist has to be on the bridge to look for whales. We have to make sure that our echo sounding system will be turned off as soon as a whale comes within 100 m distance to the ship. That is, the area around the ship is constantly being observed. In the ‘night’ from January 10th to 11th, the whale watcher noticed a small iceberg that seemed to be carrying a big black rock. Because this iceberg was on our way, we passed it after the end of the station. What we saw was not a rock but dark ice. Unfortunately, we were not able to sample this iceberg to find out the reason for the black ice.
We are surprised that we can follow the zone of low surface water salinity that we encountered at our southernmost station over an area of 900 km, always accompanied by a very high abundance of plankton. Our measurements of the exchange rate of the greenhouse gas CO2 shows that CO2 is drawn from the atmosphere into the ocean in this area. Carbon (C) is being converted into biomass by plankton. We are therefore passing through a big carbon sink.
The funny deck crew (photo: S. Fietz)
After crossing the Pacific-Antarctic Ridge the good weather was over. Because of bad weather with wave heights of 7 m, we again had to take a detour, work, and then return to start a second run towards Wellington, following the motto: ’two steps ahead, one step back’, with a quick station in between at the Polar Front. And then the unthinkable happened. January 13th, for which we had planned two additional stations, was lost upon crossing the date line and we were suddenly 12 hours ahead of the time in Germany.
On our second attempt towards the north we got as far as the Subantarctic Front, made a jump of 320 miles (ca. 600 km), always against 8 Beaufort and 4-4.5 m waves, but without a chance for sampling. Then it was over, the bad weather had passed. We went south again and managed another three stations and were thus able to complete our sampling profile between the ice edge and the Subantarctic Front. Until now, we have collected more than 900 m of sediment cores (ca. 11 t) at 64 stations, a big success!
All participants are well (also the chief-scientist is feeling better).
In the name of everyone.
Rainer Gersonde
(Chief Scientist ANT-XXVI/2)