One of the goals of the MOSES expedition mCan2018 is to analyze methane concentrations of several lakes along the highway to Tuktoyaktuk. This includes water sampling and atmospheric measurements in and above the lakes. To do that we equipped a 5 m long foldable canoe with our sensors. Given its looks, we baptized the boat “Seegurke” which is the German word for sea cucumber. The targeted lakes are close to the road. Once we selected a proper point to slip the canoe to the water, we carry it from the car to the lake. Then we attach and install a bunch of sensors.
Aboard the RV “Seegurke”
We use a “portable” Cavity Ringdown Spectrometer (CRDS) from Los Gatos to measure methane (CH4) and carbon dioxide (CO2) concentrations in the atmosphere. A laser in the spectrometer measures how gaseous samples absorb light at specific wavelengths and enables us to determine the amount of CH4 and CO2 in the sample with very high precision. It weighs 30 kg including the battery and is the heaviest sensor we drag over the tundra. But it is worth it, because the CRDS measures methane concentration in real time and indicates hot spots of methane releases.
Carrying all this stuff to the shore of the lake gets us really warm, and thus clouds of mosquitoes and black flies are following us. On the lake however, we are rewarded with their absence again. A Garmin GPS helps us to navigate through the lake and records our positions during our mini cruises. To get an idea of the bathymetry of the lake – its underwater depth and topography – we use a hydroacoustic systems with multibeam and singlebeam sensors. The sensors send out acoustic waves that are reflected by the lake bottom. The system measures how long it takes for the sound waves to bounce off the lakebed and return to the receiver – which is then used to determine water depth. Hydroacoustics also help us to spot methane releases in the water column because gas bubbles create strong reflections when hit by an acoustic wave. A sensor frame equipped with methane, nitrate and conductivity, temperature and depth sensors is aboard as well. It is deployed over the side of the canoe to take autonomous measurements in regular intervals. It not only helps to understand the geochemical properties of the lake water, but also acts as a floating anchor to challenge our paddling abilities a bit more.
Water sampling
Besides running all the electronic equipment, we are also doing the most classical work of ocean researchers: water sampling! We take water samples from different spots and depths in the lake. But we have to be patient with the analysis, since they will be processed when we are back in Germany. After taking about 8-12 two liter bottles of water samples, we are heading back to shore to unload our spoils. Then we dismantle all sensors from the canoe and carry it back to the car again. But the day is not completely over. We still need to prepare the water samples with chemicals in the lab in order to preserve them until the analysis back home.
Contributions from: Münevver Nehir
Edited by: Sina Muster