For about a week we have been operating in our investigation area, i.e. the LTER (Long-Term Ecological Research) Observatory HAUSGARTEN. In addition to our “traditional” gear to study the open and deep ocean, like water samplers, plankton nets, sediment corers and moorings, we will also deploy a number of comparably complex high-tech gear to complement our long-term studies. This includes an Un-manned Aerial Vehicles (UAV), a 3000 m depth-rated Autonomous Underwater Vehicle (AUV), free-falling lander systems (Bottom-Lander) and - for the first time in the HAUSGARTEN area - a small caterpillar, autonomously operating on the seafloor (Benthic Crawler).
During this year’s expedition we will run a total of three quadrocopters, each carrying different payloads (Fig. 1). The vehicles are 30 x 50 x 60 cm in size and weigh approximately 4 kg. As their name suggests, they are powered by four propellers. Several structural elements of the vehicle are made of bio-degradable PLA (polylactic acid) constructed using a 3D printer. During our Polarstern PS99 expedition the quadrocopters will carry different payloads, including camera systems and GPS transmitters that will be air dropped onto ice floes to track their movement. The UAV also carries a 24 megapixel compact camera that is used to systematically survey flotsam at the sea surface. These floating substrata, which may facilitate the dispersal of attached organisms over large areas, include macro algae but (regrettably) also marine litter, e.g. plastic bags and bottles. Repeated camera surveys yield valuable information on the large-scale distribution of flotsam. After the lift-off the vehicle operates on a pre-programmed transect and is surveyed by a pilot on board Polarstern. The central unit also calculates the number of images to be taken during the surveys to ultimately join single images in area-wide maps.
A second quadrocopter will be used to support the AUV dives planned in the marginal ice zone. This time the vehicle will install GPS transmitters on ice flows. The transmitters will communicate their exact position to the AUV control panel, thereby providing information about the drifting speed and direction of the sea-ice during the dive. Information about ice drift will ensure the safe navigation of the vehicle and prohibit an unintentional surfacing of the AUV under the ice.
The Autonomous Underwater Vehicle (AUV) „Paul“ (Fig. 2) is used to study physical, chemical, and biological processes in the surface layers of the ocean. The vehicle is equipped with sensors measuring temperature, conductivity and pressure, the concentration of nitrate, chlorophyll a, oxygen, CO2, coloured dissolved organic matter (CDOM), and the intensity of photosynthetically active radiation (PAR). An integrated water sampler which is able to collect 22 samples with an overall volume of 4.8 litres is used to assess the composition of plankton communities and to calibrate the nitrate and the chlorophyll a sensors. Measurements carried out with the AUV will help to develop our understanding of the complex hydrographic and biological processes occurring in melt water fronts; areas that delineate less saline waters surrounding melting ice flows and water masses of the open ocean which exhibit higher salinities.
Free-falling devices, so-called bottom-lander (Fig. 3), were deployed to conduct various physical and chemical measurements and to collect deep-sea organisms at the seabed. Such devices consist of a metal frame, weights for the descent, and floats bringing the gear back to the surface after releasing the weights. Bottom-landers may be equipped with a variety of instruments. During this cruise, we use a bottom-lander carrying incubation chambers and a micro-profiler to study re-mineralization processes at the sediment-water interface.
With great excitement we are looking forward to the first deployment of our new deep-sea rover (Benthic Crawler) “Tramper” (Fig. 4). This autonomously operating vehicle was so far only once deployed during an expedition with the German RV “Sonne” in the eastern Pacific. “Tramper” is equipped with a micro-profiler, which should take high-resolution oxygen profiles in the uppermost sediment layers. Following the initial profiling, the crawler will move for a few meters and subsequently fall asleep for a pre-set interval. “Tramper” is programmed to repeat this procedure once a week. Oxygen profiles taken with the micro-profiler will allow estimating carbon remineralisation rates in surface sediments at the deep seafloor. Whether or not “Tramper” will do its job as anticipated and will only be discovered after its recovery during another “Polarstern” cruise, already scheduled for summer 2017.
The next weekly report will provide details about the work of the phyto-opticians, biogeochemists, planktologists and sedimentologist during this expedition.
Everybody on board feels well and is in a good mood.
With best regards from all participants,
Thomas Soltwedel
