ANT-XXVI/2, Weekly Report No. 8

On the way from Chile to New Zealand, we have worked at 72 stations and recovered 1030.31 m of sediment cores with the piston, gravity and box corer. These 11.5 tons of sediment are now stored in our fridge container on the ship at 4°C. At 49 locations we used the multi-corer and collected 315 little cores of surface sediment that are now stored at -20°C in the ship’s cold room. Temperature, salinity and chlorophyll in the water column were measured 28 times using the CTD. The multi-net was deployed at 22 stations to collect plankton in the upper 1500 m of the water column at 5 depth intervals. This is complemented by water samples from the rosette and the ship’s pump, on which the nutrient concentrations and pigments as well as stable and radiogenic isotope ratios will be measured.

After our last ‘bad weather yo-yo’, we steamed 2.5 days towards Wellington over the 5000 m-deep Southwest Pacific Basin. The Parasound system showed thick sediment sequences, which we cored on January 20th and recovered a 22.83 m-long piston core. On January 21st, we reached the base of New Zealand and the water depths decreased rapidly to 1200 m, still showing a thick sediment cover. After a station on the so-called Pukaki Saddle, a depression between two underwater plateaus, some of us saw land for the first time since we left the Strait of Magellan.

At a distance of about 15 miles, we passed the Antipode Islands (60 km2) that are part of the UNESCO world heritage. They are home to an exceptional variety of birds, and landing is strictly prohibited. If you could push a long needle through the Earth’s center, it would reach the area around Cherbourg in the Normandy.

On January 22nd we reached the Bounty Trough. We wanted to core a closely spaced depth profile at water depths between 2500 m to 500 m to study the history of shallow water masses immediately south of the Subtropical Front using stable isotope ratios in foraminifera. Two days and nights we looked for good locations and recovered five sediment cores. As we reached over shallower water depths, the smell of the sediments of rotten eggs increased. This is an indication for high organic matter input.

At a water depth of ~800 m, we saw traces of gas release from the seafloor. We tried to recover another core using a 25 m-long piston core. But unfortunately the core did not penetrate more than 11-15 m of the sediment and was bent. So we had to finish our coring program with a ‘banana’, from which we still recovered a 15 m-long sediment core.

We had now reached the area of the Subtropical Front, where the water temperatures jump to above 15°C. We had therefore reached the northernmost point of our 1700 mile transect that we had started some two weeks ago in the Ross Sea. We deployed one last CTD rosette and multi-net, followed by a party to celebrate the end of the cruise. Every participant received a small piece of ‘star-dust’, a fragment of the Eltanin meteorite in memory of a long, often difficult, very eventful but still successful cruise that was coming to an end.