We have received the very sad news that Thor Aleksander Klevjer unexpectedly died in his home 13 October 2022. He was 46 years old.
Thor started his scientific career at the University of Oslo, Norway. For his PhD (2006), he applied submerged echosounders for in situ studies of individual krill and jellyfish, assessing their behavior and acoustic properties. The innovative use of acoustics for addressing biological issues subsequently became the hallmark of Thor’s work. In Oslo, he became central in establishing submerged, stationary echosounders, cabled to shore, which could be moved between different fjords depending on the scientific question to address. The establishment of such “homemade cabled observatories” and subsequent analyses and publication of results reflected Thor’s knowledge in acoustics, but also the versatility of his competence in fixing any practical issue and willingness to take on hard labor. At the University of Oslo, Thor moreover was highly appreciated by the students for his always willingness to help with their thesis work.
Subsequent to a post-doc in Oslo, including a research stay at the British Antarctic Survey, addressing Antarctic krill, Thor moved to King Abdullah University of Science and Technology (KAUST) in Saudi Arabia. He here took up studies in the Red Sea, but also participated in analyzing the large acoustic data set on mesopelagic fishes from the global Malaspina expedition, as well as continuing work in the Norwegian fjords.
For the last 10 years, Thor was employed in the Plankton Research Group at the Institute of Marine Research, Bergen. There as well, his interest in the development and use of new technologies soon became a huge asset to the research community. He continued working on submerged acoustics, and now on towed platforms taking advantage of the newest broad band technology. This brought him to study the open ocean of the North Atlantic down to mesopelagic depths and beyond. His technical ingenuity soon helped him taking advantage of the optical sensors available on the towed platform and the latest news that we received from Thor was that he now used Artificial Intelligence to identify, measure and count organisms and not least marine snow, in the water column down to 1000 m depth. With two of the Post Docs at IMR, Thor took part in the development of an acoustic method for counting and biomass estimation of single mesopelagic fish. Thor was also responsible for a work-package within an EU project coordinated by IMR, dealing with new technologies for biomass estimation of mesopelagic fishes and in that work, he also took part in the development of new trawls. However, for Thor all this new technology was only a tool, a tool to explore marine ecosystems to unravel the secrets of the organisms living deep in the open oceans. The organism’s behavior and interactions, and why they display this variety in behavior always fascinated him. Lately he also found that the data from the optical sensors could tell us a lot about carbon vertical flux, how the oceans function as a sink for atmospheric CO2. Perhaps one of the most important scientific questions today. While Thor was working mostly with mesopelagic ecosystems at IMR he also got funded a project on Antarctic krill. In this project he used moored acoustic systems in the Southern Ocean to study krill behavior in relation to their predators. Thor was a very creative and schooled scientist, but he always had time for students and his colleagues when help was needed.
While Thor for most of his career was associated with the University of Oslo and IMR, he cooperated widely both nationally and internationally. At the University of Bergen, Thor was an esteemed colleague and valued supervisor always eager to share his knowledge and data with Master and PhD students.
Thor Aleksander Klevjer represented a unique blend of competence in acoustics, marine ecology and data analyses, as well as practical skills being invaluable during field work. Combined with his pleasant personality and willingness to take on any task, this made him an invaluable colleague and friend. He will be sorely missed by his friends, colleagues and the marine scientific community at large. Our thoughts go to his family who has suffered the biggest loss. Thor was a dedicated husband to Michelle MacCarthy and the loving father of his sons Alexander Claran (7) and Elias (5). Thor is survived by his parents Gunnar and Vigdis Klevjer.
Espen Bagøien, Cecilie Broms, Tor Knutsen, Bjørn Krafft, Webjørn Melle and Espen Strand (Institute of Marine Research)
Dag L. Aksnes (University of Bergen)
Stein Kaartvedt (University of Oslo)