We use some of these ice floes that are getting thinner or thicker while crisscrossing through the Arctic Ocean, as platform for measuring devices. We often call these devices “buoys” despite the fact that not they are “buoyantly” floating but the ice floe on which they are mounted.

These devices measure a multitude of parameters, practically everything what can be measured electronically in the atmosphere, the ice or the ocean, given the sensors don’t need maintenance. The simplest ones just bear a GPS and an air pressure sensor – an important property for weather analysis and forecast in the Arctic. A little more advanced weather”buoys” measure also air temperature, humidity and wind. Other devices provide information about the growth of the ice by a 5 m long cable that reaches from the air through the snow and the ice into the water beneath. The cable is densely equipped with thermometers and through a little trick the temperature distribution gives information about the medium at the thermometer depth – snow or air, ice or water. The measurements last as long as the ice floe is drifting, the batteries endure and no polar bear tears the system apart.

Two buoys types - and here they are real buoys - are designed to measure the properties of ocean water. We have already mentioned them in the 3rd weekly report: they carry a cable of 800 m length on which a profiling sensor package moves up and down once per day, measuring ocean temperature, salinity, and oxygen content just as we do it with the many CTD systems that we lower from the ship. In addition, one of the buoy types also carries bio-optical sensors, with which we obtain information on the radiation available for photosynthesis and about a wide range of fluorescence for determining the chlorophyll content as well as that of colored dissolved organic matter that is washed into the ocean with river water.

The French version of these oceanographic buoys samples also the ice and the atmosphere in the same time. A Lidar measures the aerosol concentration and another sensor measures the optical thickness of clouds, important properties for the radiation budget and thus for the energy budget of the Arctic atmosphere. Sofar there were no measurements of these properties except a few during summer. With four of our buoys deployed, we will have for the first time four observation points throughout the year.

All ice-mounted observing systems have in common that they get their position by GPS so that they tell us the drift of their hosting floes. Moreover, through satellite communication we have all their measurements on the table in real time - hopefully for the coming couple of years.

After finishing the last ice station, we moved on towards east, and analyzing the samples from the water stations we could clearly see that we were in the Transpolar Drift that not only transports the ice form the Siberian shelves across the Arctic Ocean but also water from the great Siberian rivers. With minus 21°C we reached the new low temperature record of this summer cruise.

Unfortunately, on Thursday night we had to interrupt our research in the Siberian Arctic. We have a medical emergency case and need to evacuate a patient to Kirkenes, Norway. Despite the worry about our patient we are glad about the excellent care provided by our doctor and his assistant onboard and also about Polarstern hosting a small hospital with a telemedicine station so that specific advice can be sought from experts on land.

With our best regards from Polarstern,

Ursula Schauer

With help from Mario Hoppmann