Minik Thorleif Rosing

Abundant graphitized organic matter within 3.7-billion-year-old sediments in the Isua Supracrustal Belt comprises the oldest remnants of life. This organic matter could have provided a favorable substrate for anaerobically respiring microbes, though their existence in the early Archean remains uncertain. Here we assess whether anaerobic respiration, linked to reduction of iron and sulfur, operated within these ancient sediments. We analyzed carbon and sulfur isotope data from pelagic and turbiditic sedimentary rocks, sampled from a rock core, and used petrography and iron concentrations to provide geological context. Carbon isotopic compositions indicate respiration of organic compounds, with lighter values associated with iron-rich samples, consistent with respiration coupled to iron reduction. Sulfide grains in pelagic layers have isotopic compositions consistent with reduction of atmospherically produced elemental sulfur, possibly with minor contributions from sulfate reduction during sedimentary hiatuses. These results suggest that early Archean ecosystems were sustained by multiple, interacting microbial metabolisms.

Greenlandic glacial rock flour (GRF) is a potential source of extremely fine-grained silicate minerals for CO ₂ uptake via enhanced rock weathering. The chemical makeup of this material also indicates that it may be a good source of plant nutrients. GRF was applied at rates of 10 (GRF ₁₀ ) and 50 (GRF ₅₀ ) t ha ⁻¹ to a low-fertility sandy clay loam in Ghana to evaluate its impact on maize production relative to a control over five consecutive growing seasons. Other soil amendments, including N fertilizers, were uniformly applied across all treatments. GRF ₅₀ significantly increased grain and total dry matter yield (TDMY) across all five seasons. Seasonal increases in TDMY with GRF ₅₀ ranged from 28–87% relative to the control, and grain yield increases ranged from 28–77%. In total over the course of the five growing seasons, GRF ₅₀ produced an additional 12.9 t ha⁻ ¹ of TDMY and 7.6 t ha⁻ ¹ of grain relative to the control. GRF ₁₀ had a significant effect on TDMY and grain yield in the first two growing seasons, though the effect of GRF ₁₀ decreased over time and by the fifth growing season TDMY and grain yield were equivalent to the control. Nonetheless, the application of this lower amount of GRF still resulted in an additional 7.4 t ha⁻ ¹ of TDMY and 4.5 t ha⁻ ¹ of grain yield over the course of the experiment. These results suggest that the significant co-benefits of GRF as a fertilizer may incentivize the adoption of enhanced rock weathering in tropical, nutrient-poor environments and could increase food security in such regions.

Graphite found along contiguous horizons in the metamorphosed detrital sediments from the ≥ 3.7 Ga Isua Supracrustal Belt in Southwest Greenland may represent the oldest remains of life on Earth. Here, we examine the carbon isotope compositions of graphite occurring in situ as inclusions in minerals in both metasediment and secondary vein lithologies by secondary ion mass spectrometry. The carbon isotope composition of the metasediment-associated graphite displays a significantly narrower spread in δ¹³C values (average –20.6 ± 1.8‰, 1 standard deviation) than vein-associated graphite does (–20.4 ± 3.8‰), which can be explained by different origins, respectively interpreted as detrital biogenic matter and abiotic fluid-precipitated graphite. Additionally, graphite within metasedimentary porphyroblasts displays lower δ¹³C values (–20.9 ± 1.6‰, down to –26.4 ± 0.5‰) than graphite in the surrounding matrix (–18.1 ± 1.7‰), indicating the former to be less altered than the latter.

There is increasing recognition that the application of fine‐grained silicate rock granulates can improve soil productivity by increasing its fertility and ameliorating its physical properties. Although the former has been extensively studied, empirical information on the latter is scarce. Pot and field experiments were conducted at the University of Ghana's Forest and Horticultural Crops Research Centre (FOHCREC), Kade, Ghana, from May 2020 to December 2021 to quantify the short‐term effect of the application of Greenlandic glacial rock flour (GRF) on the physical properties of three benchmark arable soils in Ghana, namely an Acrisol (sandy clay loam), a Haplic Ferralsol (sandy loam), and an Arenosol (sand). The pot experiment included three GRF treatments (0, 10, and 20 t ha ⁻¹ ) and the three soil types, while the field experiment was conducted on only the sandy clay loam soil where GRF rates of 10 and 50 t ha ⁻¹ were compared to the control. Intact 100 cm ³ soil cores were sampled from the soil surface in the field and pot experiments to assess the soil bulk density. We also quantified soil water retention, air and gas transport, and pore morphological characteristics over a range of matric potentials. Both the pot and field experiments showed that adding GRF did not improve soil water retention. Still, the response of gas transport and pore characteristics to changing matric potential was significantly ( p < 0.05) modified by GRF in some soil types. The results suggested that the effectiveness of the use of GRF to ameliorate soil physical conditions for plant growth may depend on soil type and the soil water matric potential. We concluded that the application of GRF cannot be relied upon as a short‐term strategy to significantly improve the structural quality of the tropical soils studied. Rather, GRF should be considered for application to the soils for its other beneficial effects. We recommend that the effects of repeated applications and further build‐up of the material in the soil should be investigated to determine the effect of higher relative GRF concentrations on soil hydro‐physical properties.

Plate tectonic processes modulate element cycling, crust generation, and differentiation, yet at what point in Earth’s history these processes emerged remains debated. Here we present evidence that parts of the >3.7 Ga Isua Supracrustal Belt formed within a fore-arc setting, consistent with the operation of plate tectonics in the Eoarchean. We show that the oldest known sequence of detrital meta-sedimentary rocks were deposited conformably above chemical sediments on a volcanic basement. Mineral and trace elemental compositions show that turbiditic and pelagic detrital sediments were derived from terrains, comprising both basalts and differentiated tonalitic igneous rocks. The boninitic volcanic basement would have formed in a tensile environment before the adjacent terrains which sourced the clastic sediments. This suggests formation within a fore-arc during the initial few million years of subduction. This environment may have facilitated the local proliferation of life suggested by the frequent occurrence of layers rich in biogenic graphite.

Although Greenland is a hub for climate science, the climate perceptions of Greenland’s predominantly Indigenous population have remained largely unstudied. Here we present two nationally representative surveys and show that Greenlanders are more likely than residents of top oil-producing Arctic countries to perceive that climate change is happening and about twice as likely to have personally experienced its effects. However, half are unaware that climate change is human-caused and those who are most affected appear to be least aware. Personal experience and awareness of human-induced climate change diverge along an Inuit cultural dimension. Indigenous identity positively predicts climate change experience, whereas subsistence occupation and no post-primary education negatively predict attribution beliefs. Despite Greenland’s centrality to climate research, we uncover a gap between the scientific consensus and Kalaallit views of climate change, particularly among youth. This science–society gulf has implications for local climate adaptation, science communication and knowledge exchange between generations, institutions and communities.