Danish Ministry of Climate, Energy and Utilities

This study integrates process-based hydrological modeling and empirical CO2 flux modeling at a daily temporal resolution to evaluate how peatland hydrology influence CO2 emissions under scenarios of rewetting and climate change. Following the calibration of a three-dimensional transient physically-based hydrological model for a peat-dominated catchment, daily groundwater table dynamics were simulated to represent hydrological conditions in drained peat soils. These simulations were coupled with an empirical CO2 flux model, developed from a comprehensive daily dataset of groundwater table depth, temperature, and soil CO2 flux measurements. The empirical CO2 flux model captures a clear temperature-dependent response of soil CO2 emissions to variations in groundwater table depth. By applying this coupled modeling framework, we quantified CO2 emissions at daily timescales. The results demonstrate that incorporating both temperature sensitivity and high-resolution temporal variability in water level significantly influences projections of CO2 fluxes. Especially the co-occurrence of elevated air temperature and low groundwater table significantly influence CO2 emissions under scenarios of rewetting and climate change. These insights highlight the importance of including changing climate conditions in future peatland management strategies for emission inventories. The study illustrates the value of combining detailed hydrological simulations with emission models. It also emphasizes the need for detailed monitoring of greenhouse gas emissions across multiple sites and the development of robust empirical models that can be generalized and spatially upscaled.

This article reviews existing and planned contributions of spaceborne microwave radiometry from P to S band to new measurements of key geophysical variables with a particular focus on the polar regions. It summarizes the current state of spaceborne microwave radiometry to measure ice sheet thermal states, sea ice thickness (SIT), salinity, and sea surface salinity (SSS). Then, this article discusses the potential of wideband radiometry, with continuous sampling in the range of 0.4-2 GHz, as a breakthrough for enhancing the estimation of geophysical variables such as SSS and the geothermal heat flux beneath the polar ice sheets, which are currently monitored primarily using L-band radiometry satellites. Furthermore, this article describes opportunities for new unique observations that cannot be achieved with the current constellation of satellite sensors. In addition, this article demonstrates the advantages of using low-frequency radiometry in sensing soil moisture and biomass from space due to the great sensing depth. This article concludes with a discussion of mission concepts highlighting the CryoRad mission, which has been selected as one of the four candidates for European Space Agency Earth Explorer 12 competition and is now conducting Phase 0 feasibility studies, envisions a 0.4-2-GHz dedicated spaceborne radiometer operated with circular polarization.

The continental crust is significantly depleted in Cu relative to primary arc magmas, yet the mechanisms governing Cu redistribution in the lower crust remain unresolved. Understanding Cu behavior during magma differentiation is crucial for constraining the formation of deep-crustal copper reservoirs. This study investigates Cu isotopic compositions of lavas from the Andagua Valley in the Central Volcanic Zone (CVZ) and reveals delta o5Cu variation ranging from 0.08%o to 0.65%o. Garnet fractionation under high-pressure conditions reduces FeOT contents in the magma, lowering sulfur solubility and promoting early sulfide saturation. However, sulfide segregation is dominated by monosulfide solid solution (MSS) and occurs under high-temperature conditions, which together significantly limit Cu isotope fractionation. Rayleigh fractionation modeling shows that the average mineral-melt fractionation factor (Delta o5Cumineral-melt value) is between-0.3%o and-0.1%o, demonstrating that fractionation is present but not quantitatively significant. Consequently, Cu isotopes in CVZ magmas exhibit fractionation during deep-crustal differentiation, with delta o5Cu signatures remaining in a certain range. The delta o5Cu variation in CVZ magmas contrasts with the significantly broader range in the lower crustal cumulates ranging from-3.16%o to 2.89%o, marking a fundamental shift in Cu behavior as magmas transition from high-temperature differentiation to prolonged cooling in the lower crust. We propose that lower crustal cumulates evolve through extended differentiation, where temperature-dependent isotope fractionation leads to significantly greater delta o5Cu variations. Prolonged cooling further promotes sulfide accumulation and post-cumulus interactions, leading to Cu redistribution and ultimately contributing to the formation of deep-crustal Cu reservoirs.

The release of microplastics (MPs) from nylon tea bags poses a critical concern for human exposure; however, their detection and quantification remain challenging especially in beverage matrices, and hence, this study pioneers the use of high-resolution optical coherence tomography (OCT) integrated with an image processing algorithm to rapidly detect and quantify the size and count of the MPs directly in the water extractions simulating tea brewing. The water extractions prepared by simulating tea brewing conditions, hot (100 °C, 1-5 min), cold (2 °C, 1 h), and ambient (30 °C, 1 h), were observed employing OCT imaging and validated through Nile Red (NR) staining and digital microscopy. The nylon tea bags steeped in hot water for 5 minutes released 16 000 to 24 000 LMPs (>30 µm) and SMPs (12-30 µm) per millilitre. The estimated daily intake (EDI) of MPs indicates a higher exposure for children (ranging from 0.201 to 0.349 mm3 kg-1 day-1) compared to adults (0.046 to 0.080 mm3 kg-1 day-1). In contrast, cold brewing for 1 hour released fewer LMPs but an equal quantity of small MPs (SMPs) compared to hot brewing. This OCT-based approach offers a rapid, versatile platform for the detection and quantification of MPs from diverse packaging materials and provides a powerful tool for comprehensive risk assessment when combined with chemical and toxicological analyses.

As the Arctic warms, surface melt extends into the Greenland Ice Sheet's accumulation zone, where much of the water infiltrates into the snowpack. This makes monitoring the subsurface water depth and spatial extent important for accurate ice sheet runoff estimations. Subsurface water can be detected using remotely sensed microwave brightness temperatures (TB). We use vertically polarized TB at 1.4 GHz from Soil Moisture and Ocean Salinity satellite (SMOS) and at 6.9, 10.7, and 18.7 GHz from the Advanced Microwave Scanning Radiometers (AMSR-E/2) to estimate the upper depth of liquid water (UDLW) on the ice sheet accumulation area. We build a catalogue of simulated UDLW and TB: realistic UDLW are modeled by the Geological Survey of Denmark and Greenland (GEUS) snow model, forced by the Copernicus Arctic Regional Reanalysis (CARRA), and the corresponding TB are calculated by the Snow Microwave Radiative Transfer (SMRT) model at 19 sites. We train on this catalogue an ensemble of cross-validated Random Forest (RF) models to predict UDLW and its uncertainty from TB at four frequencies. On hold-out modeled data and for water within 5 m of the surface, the RF ensemble achieves a median RMSE of 0.68 m and mean error of -0.09 m. Our retrieval, when applied to observed TB, matches within 2 m UDLW inferred from subsurface temperature profiles down to 4-6 m depth. Performances decrease beyond 5 m depth and for low liquid water amounts. Our retrieval produces daily UDLW maps over the ice sheet's accumulation area during 2010-2023 which reveal the seasonal evolution of UDLW, deliver the first quantitative estimates of subsurface liquid water depth on the ice sheet and offer new insights into meltwater infiltration and storage processes.