Periodic Reporting for period 1 - ICEotopes (Assessing the Response of Marine Macro- and Micronutrient Bioavailability and Cycling to Arctic Sea-Ice Loss)
Reporting period: 2022-09-01 to 2024-08-31
Sea-ice loss, freshening and stratification changes in the recent past have affected, and are projected to continue to affect, the timing, distribution and biomass production of Arctic primary producers. Current enhancements observed in primary production are attributed to increased light penetration associated with sea-ice thinning and loss. However, these enhancements may be a relatively short-term phenomenon that will recede unless there is additional supply of nutrients to the photic zone. In addition to external inputs through rivers, atmospheric deposition and vertical mixing, internal cycling and redistribution related to sea-ice formation, transport and melting are important mechanisms affecting nutrient distributions in the Arctic Ocean. Quantifying the individual contributions of these processes to nutrient bioavailability and cycling is imperative in light of ongoing sea-ice retreat but currently hindered by the lack of studies applying source- and process-sensitive tracers. Therefore, I will develop a multi-tracer approach based on a suite of innovative isotopic tracers sensitive to nutrient sources and cycling to be determined in snow, sea ice and seawater obtained from the year-round MOSAiC initiative and from multiple summer cruises to the Arctic Ocean. By combining established and new analytical techniques in trace element and isotope geochemistry and by conducting laboratory-controlled sea-ice growth experiments, this innovative and interdisciplinary approach will take advantage of cutting-edge knowledge in tracer development and behavior without compromising on the benefit of a seasonally and spatially constraint dataset. The results will provide a deep understanding of the effects on - and feedbacks within – Arctic marine ecosystems arising from sea-ice loss, reduce uncertainties associated with bioengineering-inspired carbon sequestration efforts and complement Europe’s 2020 strategy to tackle Food Security and Climate Action objectives.
The project ICEotopes set out to understand how the rapid loss of Arctic sea ice is reshaping the cycling of nutrients that sustain marine life. To achieve this, innovative chemical “fingerprints” – isotope tracers – were developed and applied to reveal the sources and transformations of key nutrients such as silicon, barium, cadmium, and zinc. Laboratory freezing experiments carried out under controlled conditions generated new datasets that simulate sea-ice growth and document how nutrients and trace elements are redistributed between ice and seawater. These results provide fresh insight into abiotic processes that were previously poorly understood. In parallel, major effort was invested in advancing isotope measurement techniques, enabling detection of very small changes in nutrient chemistry with high precision. Complementary analyses were conducted on samples collected during the international MOSAiC expedition and several Arctic summer cruises. These unique snow, sea-ice, and seawater samples now underpin the first comprehensive isotope datasets of their kind. Early findings demonstrate that concentrations of some trace metals (Cd, Zn) are too low to permit isotope analysis in Arctic sea ice based on available samples—an important result in itself, as it highlights the physicochemical limits of the system and helps identify the most suitable tracers. In addition, a strong influence of the parental seawater composition on trace-element distributions in sea ice has been observed. Overall, the project has fully met the objectives set for this reporting period, providing novel experimental and field data, refining analytical methods, and laying the foundation for large-scale observational studies of nutrient fluxes in the Arctic Ocean.
ICEotopes is moving research beyond the state of the art by applying a multi-isotope approach to Arctic sea ice, something that has never been attempted systematically before. Traditional studies relied mainly on bulk nutrient concentrations, which could not separate the effects of physics from biology. The new isotope tracers make it possible to distinguish abiotic nutrient redistribution during ice growth and melting from biological uptake and remineralization. This represents a major step forward in our ability to quantify how the loss of sea ice affects the nutrient balance of the Arctic Ocean.
By the end of the fellowship, the project will deliver the first integrated assessment of nutrient fluxes across the atmosphere-ice-ocean system. These results will allow researchers to forecast how continued Arctic warming and sea-ice retreat may alter marine productivity, with consequences for fisheries, food webs and carbon cycling. The findings will be directly relevant to international assessments such as the IPCC reports and to European strategies on Food Security and Climate Action. The wider societal implications are also significant. The Arctic Ocean is undergoing the fastest environmental change on the planet, with global repercussions. By clarifying how nutrients are supplied and recycled in this fragile system, ICEotopes provides critical knowledge for predicting the resilience of marine ecosystems and for evaluating potential geoengineering or resource management options. The project also contributes to training the next generation of polar scientists, strengthening international research networks, and informing the public and policymakers about the impacts of climate change in the Arctic.
By the end of the fellowship, the project will deliver the first integrated assessment of nutrient fluxes across the atmosphere-ice-ocean system. These results will allow researchers to forecast how continued Arctic warming and sea-ice retreat may alter marine productivity, with consequences for fisheries, food webs and carbon cycling. The findings will be directly relevant to international assessments such as the IPCC reports and to European strategies on Food Security and Climate Action. The wider societal implications are also significant. The Arctic Ocean is undergoing the fastest environmental change on the planet, with global repercussions. By clarifying how nutrients are supplied and recycled in this fragile system, ICEotopes provides critical knowledge for predicting the resilience of marine ecosystems and for evaluating potential geoengineering or resource management options. The project also contributes to training the next generation of polar scientists, strengthening international research networks, and informing the public and policymakers about the impacts of climate change in the Arctic.