PS106/1 - Weekly Report No. 3 | 5 - 13 June 2017
Week 1 at the ice floe
After successfully building up all measurement sites we now have reached a full week with a multitude of observations. This report provides a few examples of what and how we are measuring in our little white floe, we call our home. Oddly enough we didn't manage to give it a name, probably because we all know that it will soon be gone.
With contributions from Ulrike Egerer, Hauke Flores, Allison Fong, Ilka Peeken, Priit Tisler
Algae that grow in the bottom part of the ice maintain a unique ecosystem that can only be found in the Polar Regions. Within the branched brine channels of the ice, in the niches at its bottom part and between stacks of ice blocks small animals that feed on ice algae find refuge. The habitat of these animals is very difficult to reach. Correspondingly, little is known about their distribution, frequency and way of life.
At the ice bottom there exist mostly copepods with sizes of 0.5 - 5 cm as well as amphipods. To find out more about these animals, biologists and sea ice physicists at AWI have developed a special research net. By means of a cable-operated under water measuring unit or Remotely Operated Vehicle (ROV), the so called ROVnet, can probe organisms from the ice bottom. A bristle comb so to speak "sweeps" along the ice from below (see Fig. 1).
On PS106.1 the ROVnet was taken into the water in the Arctic for the first time. We were very relieved as we saw how well this technically simple research device worked at its first operation. The first catches were teeming with copepods and amphipods. Within few ROVnet casts the whole spectrum of expected species was nearly fully retrieved.
On this flow we were lucky to find a region were the algea Melosira arctica“, alga of the year 2016, is living on the ice bottom. On an expedition in 2012 that nearly went to the North Pole we could prove that this alga is an important source of nutrition for organisms living at the sea floor. These algae consist of tiny cells, but build large chains of those that can reach up to several meters in size. Small forests of this species are than hanging below the floe (see Fig. 2). In order to investigate the adaptability of these algae to changing light conditions through the melting ice, we manipulate the light with different snow loads.
Regular probing will take place in this region to identify the optimal life conditions for these algae. In addition we want to find out, which part the current plays for the growth of the algae.
A suite of biological and biogeochemical samples are collected from the water column on a daily basis to observe the temporal evolution of the plankton community and the essential nutrients they utilize. Additionally, we are interested in understanding the linkages between pools of carbon, nitrogen, and other elements in seawater, sea ice, and the atmosphere. Therefore, concentrations of trace gases (i.e. methane) and particulate pools of carbon and nitrogen are sampled from the seawater to ascertain fluxes across different interfaces. In addition to these observations, several experiments are underway to elucidate the mechanisms which control gas fluxes, controls on primary productivity, and carbon and nitrogen cycling. Some groups are specifically interested in how light and additional nutrients can alter the rate of specific processes, such as primary productivity and nitrogen fixation. These experiments are conducted through a combination of shipboard water collections and in situ incubations under the ice. We work closely with other groups onboard to examine the linkages between pelagic waters and sea ice environments.
Two days after arriving at our ice floe, the tethered balloon was ready for its daily operations. Back home, we had developed different sensor packages, which can be attached to our 90m2 Helium-filled balloon in different configurations (see Fig. 3) to measure vertical profiles of the Arctic atmospheric boundary layer. We retrieve turbulence and turbulent fluxes as well as radiative fluxes to derive the radiation budget and heating rates of clouds. We are mainly interested in measuring within low-level clouds, so we were happy with the weather conditions of the first week with clouds and moderate wind.
A team of two people from The Finnish Meteorological Institute and The University Centre in Svalbard is operating UAVs on our ice floe: a fixed wing UAV and a quadrocopter (see Fig. 4), each of which is equipped with sensors for the measurement of temperature, relative humidity, pressure and they can also estimate the wind. Several UAV flights have been conducted so far, focusing on the lowest hundreds metres of the atmosphere; the boundary layer. The UAV measurements nicely complement those from other platforms deployed during the expedition, such as a tethered balloon, weather balloons (radiosondes), lidars and conventional weather masts.
The same team also operated the UAVs during an expedition in Antarctica with Polarstern during the austral winter of 2013. In spite of more modest temperatures and 24 hours daylight, operating UAVs during this Arctic expedition has proven more challenging than in Antarctica. Especially the visibility and for parts of the time also strong winds, have limited the number of UAV operations. The visibility is not only important for observing the aircraft, but also important for spotting polar bears that might be in the area.
After the short visit at the beginning of the week we haven't seen any polar bears so far, although we spotted some seals. Several times we had to cancel our measurements in the ice due to low visibility. Also the two AWI Polar aircrafts Polar 5 and Polar 6 could not take off from Longyearbyen for the planned flights in the area of Polarstern for several days due to bad weather conditions. However, all in all the first week has yielded many nice measurement situations, especially since we now arrived in the melting period, but more of that in the next and last report of the section PS106.1
Best regards from Scientists and Crew,
Andreas Macke, chief scientist