On the 2nd August 2023, I (BIOPOLE researcher Dr Kathryn Cook, University of Exeter) joined the RV Polarstern in Tromsø, along with project partners Morten Iversen and Sinhue Torres-Valdes (AWI), to participate in the 9-week ArcWatch 1 (PS138) cruise to the central Arctic. The overall aim of the 50 scientists participating on the cruise was to study the physics, chemistry, and biology of the sea ice, but I was invited along to collect samples to help address BIOPOLE WP2 deliverable ‘What controls the depth at which polar copepods diapause, and their physiological rates during overwintering?’.
I used a Hydro-Bios Midi Multinet (thanks to project partner Barbara Niehoff, AWI) to sample the important Arctic lipid storing copepods Calanus hyperboreus, Calanus glacialis, and possibly the northern North Atlantic interloper Calanus finmarchicus (we’ll have to wait for molecular confirmation to find out) throughout the upper 1500m of the water column. I was also able to take samples from immediately below the sea ice using a net attached to an ROV affectionately known as ‘The Beast’. We took samples at 9 ice stations, including the MOSAiC station and the North Pole. These samples will be used to quantify the biomass (carbon and nitrogen), lipid content and composition, and estimate the metabolic rates using enzyme assays (Electron Transport System (ETS) activity as a measure of respiration rate; Amino-Acyl-t-RNA-Synthetases (AARS) activity as a measure of growth). These data will be used to inform life-cycle food-web models and will be available to WP3 to help develop simplified, global parameterisations of the lipid pump and improve estimates of the amount of carbon sequestered in the mesopelagic ocean.
As well as being very successful scientifically, this cruise was, by far, the most exciting research trip I have been on in my career to date. Just getting out on the sea ice was amazing, but we also had helicopter excursions to measure ice thickness, a polar bear coming to play with ‘The Beast’, live footage of sea mounts and hydrothermal vents courtesy of the OFOBS (Ocean Floor Observation and Bathymetry), live music courtesy of The ArcWatchers (featuring project partner Morten Iversen) and of course being, literally, on top of the world. We were accompanied by a media team who wrote regular social media posts, blogs (Arctic August – October 2023 – AWI Polarstern) and German newspaper articles, as well as a documentary film crew. The documentary ARCWATCH – HOPE IN THE ICE was broadcast on 29 December 2023 at 9:45 p.m. by German broadcaster ARD and is available (in Germany) in the ARD Media Library. There should be an international version released at some point, so watch this space.