Subsea permafrost represents a large carbon pool that might be or become a significant greenhouse gas source. Scarcity of observational data causes large uncertainties. We here use five 21-56 m long subsea permafrost cores from the Laptev Sea to constrain organic carbon (OC) storage and sources, degradation state and potential greenhouse gas production upon thaw. Grain sizes, optically-stimulated luminescence and biomarkers suggest deposition of aeolian silt and fluvial sand over 160 000 years, with dominant fluvial/alluvial deposition of forest- and tundra-derived organic matter. We estimate an annual thaw rate of 1.3 ± 0.6 kg OC m−2 in subsea permafrost in the area, nine-fold exceeding organic carbon thaw rates for terrestrial permafrost. During 20-month incubations, CH4 and CO2 production averaged 1.7 nmol and 2.4 µmol g−1 OC d−1, providing a baseline to assess the contribution of subsea permafrost to the high CH4 fluxes and strong ocean acidification observed in the region.

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Hypothesis-based reasoning with conditionals is a skill that is required for engaging in integral activities of modern elementary school science-curricula. The teaching of this skill at this early stage of education, however, is demanding, particularly in whole school classes in which it is difficult to adapt teaching to children’s individual needs. We examine whether a scaffold that is static yet tailored to the context, in which the teacher explicitly models the reasoning process, manages to meet students’ individual cognitive preconditions for learning this skill. Within an inquiry-based learning setting, N = 143 third-graders underwent either an experimental condition in which they received the explicit scaffold, or a control condition in which they did not receive this specific scaffold. Employing a latent transition analysis and a general additive model, it is examined how the additional scaffold interacted with students’ prior knowledge, inhibition ability, and logical reasoning judged by their own teachers. It is found that the additional scaffolds managed to meet the needs of students with little prior knowledge; under the control condition, students with little prior knowledge showed decreased learning achievement, whereas under the experimental condition, students with differing prior knowledge learned to comparable extent and on a higher level. The scaffolds also almost fully diminished a disadvantage for students with lower teacher-judged logical reasoning, and supported students with high inhibition ability in mastering the most difficult aspect of reasoning based on irrelevant evidence. Implications for science education are discussed.

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