PS110 - Weekly Report No. 1 | 20 December 2017 - 3 January 2018
From Advent into the New Year
According to the schedule Polarstern left Bremerhaven at high tide and in tight fog on 20th December, 2017. On board are 44 crew members and 9 scientists. There are also 2 inspectors of Laeisz Shipping Company and 4 engineers and technicians from companies in duty of last jobs left over from the ship-yard time of the vessel.
Due to the exceptional late start of the transit cruise to Cape Town because of the long dockyard time of Polarstern, the number of scientists during leg PS110 is relatively low. This results in a tight cruise schedule, which does not allow any station time for research except for a few hours only for equipment testing. Among acquisition of basic parameters of the hydrosphere and atmosphere along the ship’s track it is the main goal of the scientific work during PS110 to test re-engineered equipment in order to make it work for forthcoming expeditions.
After a very short port call at Le Havre for taking on board important equipment we leave the English Channel on December 24 in cold and wet, but still relatively calm weather. On Christmas Eve, our location is west of Brittany in the Golf of Biscay. We have punch and a Christmas tree and the festive mood is a comfort to us because we all miss our family members at home. On Christmas Day in the Gulf of Biscay, a period of very calm weather, lasting for days, ends with a frontal system passing through coming along with gale-force winds of 7 to 8 Bft. The related swell of up to 3 m does not affect Polarstern too much so that we can fully enjoy the roast Christmas goose in the mess lovingly decorated by the stewardesses and stewards. Thanks to the good forecast of our colleagues of the board-weather office we could just escape from the infamous sea area of the Gulf of Biscay especially in winter times. Only one or two days later, the swell reached 6 to 8 m again. At this time, Polarstern comes already close to the Azores anticyclone. Consequently, temperatures on deck become significantly warmer and the wind calms down.
During the first part of the journey, the scientific work is focused on two topics. First, the completely re-engineered radiosonde system of the board-weather office is implemented and tested by the colleagues from the AWI section of atmosphere physics and the board-weather technician from DWD. On Polarstern, daily radiosonde profiling is carried out by a balloon-carried system acquiring data of atmospheric temperature, moisture and wind from ground up to 35 km height. The data is transferred into a world-wide network of meteorological stations and helps to improve weather forecasting. Second, the hull-mounted scientific echo-sounding system PARASOUND, recently re-engineered, is tested continuously along the ship’s track. The device is needed on forthcoming expeditions in order to investigate the top 100 to 200 m of ocean-floor deposits by means of acoustic waves. Data are used to analyze depositional conditions in different environments and their changes in space and time. In addition, the information is used to select geological sampling locations.
The next stopover along our journey is Las Palmas on the island of Gran Canary on 28th of December 2017. After a farewell barbecue on the working deck the night before kindly provided by the ship’s galley, 3 colleagues from the atmospheric science group and 7 engineers, technicians and inspectors are leaving us after their successful work is finished. One colleague of the AWI logistics department comes on board, and the vessel is fully re-bunkered. At 18:00, and as a fair coincidence, we (“Polarstern 1”) is leaving Las Palmas port together with the cruise liner “Queen Elizabeth-3” at cloudy and rather cool weather to carry on our journey southwards.
With the sea and the northern trade winds from behind, Polarstern is making good distance during the last days of 2017. At New Year’s Eve we have already reached the sea area east of the Cape Verde Islands. Air temperatures of 20° C provide perfect conditions to let the year of 2017 end while having a barbecue on the working deck. At midnight, there is no firework since at sea any illumination rockets can be misinterpreted as distress rockets. We are using the ship’s typhon welcoming the New Year with a glass of sparkling wine for those not being on watch. On Wednesday, 3rd of January 2018, Polarstern is already at the southern end of the Sierra Leone Basin and only about 350 km away from the equator. Accordingly, there are hot temperatures outside. At about 30°C, occasional thunderstorm showers are crackling on deck. We have left the region of the trade winds and are crossing the inner-tropical convergence zone. On the evening of the 2nd of January, many flying fishes take off next to the ship for escape, and turtles are spotted. Several dolphins approach the vessel only at a few meters distance. Obviously, they enjoy a foam bath in the bow wash of the ship before submerging in front of the vessel. To protect the animals, the PARASOUND system is switched off during this performance.
On the leg between Las Palmas and Cape Town, the scientific program focusses on two topics. First, extensive test runs of the PARASOUND systems are carried out. In particular, along the deep-sea areas between the Canary Islands and the Sierra Leone Basin south of the Cape Verde Islands at water depth between 3000 and 5000 m, sedimentary conditions below the sea floor are perfectly suitable in order to test new features of the system for better sound penetration and/or resolution of depositional structures. Second, we have to test components of another echo sounder system (EK-80), which is used by biologists for stock assessment of fish, krill and other organisms in the water column. The EK-80 re-engineering has been carried out before the cruise, which make calibrations at sea necessary. For this reason, on 2nd of January, Polarstern stops for about 2.5 hours in completely calm sea conditions. The mobile unit of the EK-80 system, normally used under expedition conditions in a towed system behind the vessel, is deployed in the water next to the ship hanging on a crane wire. For calibration purposes, a small steel bowl of known size is exposed into the acoustic beam a few meters below the transducer. The station time is also used to deploy an inflatable boat in order to test a Mini-ROV at some distance from Polarstern. This is a mini-underwater robot, which is used amongst other duties to help calibrating and monitoring the hull-mounted component of the EK-80 system.
All on board are well and in good mood.
We send our best wishes to all our families and friends at home.
(Polarstern, 3° 20' N, 16° 21' W, 3.1.2018)