ALBERT

Description: Magnetic helicity is an important concept in solar physics, which can be carried away through the photosphere into the corona, plays an important role in solar flares and coronal mass ejections (CMEs). Here we force on two questions: 1. the relationship between the accumulated magnetic helicity flux through photosphere () and the relative magnetic helicity in the corona (); 2. the change ratio of magnetic helicity () during major flares. We reconstruct the 3D coronal magnetic field using nonlinear force free field (NLFFF) extrapolation from observed photospheric magnetograms, and the accumulated magnetic helicity flux is derived from successive magnetograms by optical flow methods (LCT and DAVE). The DAVE-based is more consistent with than LCT-based , and is more consistent with in evaluation from 2’’ than from 1’’. These results suggest the consistency of and is partly dependent on the resolution of the magnetograms and the calculation methods. The flare samples are divided into two groups: the 18 no-CME-associated confined flares and 29 CME-associated eruptive flares. Five different schemes are adopted to overcome the dependence of magnetic helicity estimation on the spatial resolution. In one typical scheme, as an example, the median value of is -1.2% for confined flares, while this number is -15.0% for eruptive flares. These calculation and analysis statistically confirm that, magnetic helicity is approximately conserved in the magnetic reconnection and the CMEs take away part magnetic helicity from the corona.

Description: The low Antarctic sea ice extent (SIE) following its dramatic decline in late 2016 has persisted over a multiyear period. However, it remains unclear to what extent this low SIE can be attributed to changing ocean conditions. Here, we investigate the causes of this period of low Antarctic SIE using a coupled climate model partially constrained by observations. We find that the subsurface Southern Ocean (SO) played a smaller role than the atmosphere in the extreme SIE low in 2016, but was critical for the persistence of negative anomalies over 2016-2021. Prior to 2016, the subsurface SO warmed in response to enhanced westerly winds. Decadal hindcasts show that subsurface warming has persisted and gradually destabilized the ocean from below, reducing SIE over several years. The simultaneous variations in the atmosphere and ocean after 2016 have further amplified the decline in Antarctic SIE.

Description: Our lack of understanding with respect to the sources and nucleating capabilities of natural aerosol in the high Arctic is one reason why Arctic clouds are still poorly represented in climate models. Recent field campaigns provide evidence of a source of sea salt aerosol (SSA) from blowing snow above sea ice, which can account for the SSA winter/spring maxima observed in the Polar Regions. This SSA has the potential to influence the regional climate through the indirect radiative effect, but the relative magnitude of its contribution to cloud forming particles, especially ice nucleating particles (INP), are still largely unknown. For this presentation we use online and offline measurements of airborne aerosol for its ice nucleating properties that were carried out in the Central Arctic during MOSAiC. We combine these with INP measurements from snow samples, observations of snow particle fluxes, and aerosol measurements from the comprehensive MOSAiC data set. Online observations of INP in spring show concentrations in the order of a few tens [particle m-3], that were often associated with high wind speeds. Initial offline analyses of snow samples from the sea ice taken during the same period indicate the presence of INPs. This is evidence that snow on sea ice represents a viable source of INPs, which may release these particles via blowing snow into the atmosphere.

Description: This dataset contains predictions of Earth orientation parameters (EOP) submitted during the Second Earth Orientation Parameters Prediction Comparison Campaign (2nd EOP PCC). The 2nd EOP PCC has been carried out by Centrum Badań Kosmicznych Polskiej Akademii Nauk CBK PAN in Warsaw in cooperation with the GFZ German Research Centre for Geosciences in Potsdam (Germany) and under the auspices of the International Earth Rotation and Reference Systems Service (IERS) within the IERS Working Group on the 2nd EOP PCC. The purpose of the campaign was to re-assess the current capabilities of EOP forecasting and to find most reliable prediction approaches. The operational part of the campaign lasted between September 1, 2021 and December 28, 2022. Throughout the duration of the 2nd EOP PCC, registered campaign participants submitted forecasts for all EOP parameters, including dX, dY, dPsi, dEps (components of celestial pole offsets), polar motion, differences between universal time and coordinated universal time, and its time-derivative length-of-day change. These submissions were made to the EOP PCC Office every Wednesday before the 20:00 UTC deadline. The predictions were then evaluated once the geodetic final EOP observations from the forecasted period became available. Each participant could register more than one method, and each registered method was assigned an individual ID, which was used, e.g., for file naming. The dataset contains text files with predicted parameters as submitted by campaign participants and MATLAB file which is a database with all correct predictions from each participant loaded into a structure.

Description: Apatite is a ubiquitous phase in granite plutons and in most adjacent country rocks, thus contamination of a granite magma with wall-rock material results in two genetic types of apatite in the magma: cognate and foreign. These two textural and chemical varieties of apatite undergo textural and compositional changes to reach physical and chemical equilibrium (perfect assimilation) in the melt. Our experiments replicate the conditions in such contaminated granites. The starting materials consist of a peraluminous synthetic SiO2-Al2O3-Na2O-K2O (SANK 1.3) granite gel with A/NK of 1.3, synthetic F-apatite, synthetic Cl-apatite, and natural Durango apatite. Initial experiments in cold-seal hydrothermal pressure vessels at magmatically realistic temperatures of 750 °C and pressures of 200 MPa produced negligible reactions, even after run times of 2000 h. Instead, we used an argon-pressurized internally heated pressure vessel with a rapid-quench setup at temperatures of 1200 °C, pressure of 200 MPa, and run durations of 192 h. An advantage of this high temperature is that it exceeds the liquidus for quartz and feldspar; therefore, apatite is the only solid phase in the run products. The starting composition of each run was 90 wt% SANK 1.3 granite gel and 10 wt% crushed apatite (consisting of one, two, or three varieties), with and without 4 wt% added H2O. Run products were examined by SEM for texture and by EMPA and LA-ICP-MS for composition. The starting synthetic granite composition contains no Ca, F, Cl, or REEs thus, in every run, apatite was initially undersaturated in the melt. In all experiments, most large apatite grains consisted of anhedral shards with rounded corners, most small apatite grains were round, and a small proportion of apatite grains developed one or more crystal faces. In experiments with two or three apatite compositions, the run-product apatite grains had compositions intermediate between those of the starting-material grains, and they were homogeneous with respect to Cl, and probably F, but not with respect to REEs. The processes to reach textural equilibrium consist of dissolution until the melt is saturated in apatite, followed by Ostwald ripening to eliminate small grains and to develop crystal faces on larger ones. The processes to reach chemical equilibrium consist of dissolution of apatite, diffusion of cations (Ca, P, REE) and anions (F, Cl, OH) through the silicate melt, and solid-state diffusion in the undissolved apatite grains. The halogens approached chemical equilibrium in all experiments, but in the experiments containing Durango apatite, the REEs have not. Models involving radial diffusion into spherical apatite grains at the temperatures of the experiments show complete re-equilibration of the halogens, but changes in the REE concentrations affecting only the outer few micrometers. We conclude that the rate of chemical equilibrium for the halogens is greater than the rate of physical equilibrium for texture, which in turn is greater the rate of chemical equilibrium for REEs. We illustrate these processes with a natural example of contaminated granite from the South Mountain Batholith in Nova Scotia. Given that all granites are contaminated rocks, we propose that future petrogenetic studies focus on developing techniques for a minerals-based quantitative estimation of contamination (QEC).

Description: Global climate warming is accelerating permafrost degradation. The large amounts of soil organic matter in permafrost-affected soils are prone to increased microbial decomposition in a warming climate. Along with permafrost degradation, changes to the soil microbiome play a crucial role in enhancing our understanding and in predicting the feedback of permafrost carbon. In this article, we review the current state of knowledge of carbon-cycling microbial ecology in permafrost regions. Microbiomes in degrading permafrost exhibit variations across spatial and temporal scales. Among the short-term, rapid degradation scenarios, thermokarst lakes have distinct biogeochemical conditions promoting emission of greenhouse gases. Additionally, extreme climatic events can trigger drastic changes in microbial consortia and activity. Notably, environmental conditions appear to exert a dominant influence on microbial assembly in permafrost ecosystems. Furthermore, as the global climate is closely connected to various permafrost regions, it will be crucial to extend our understanding beyond local scales, for example by conducting comparative and integrative studies between Arctic permafrost and alpine permafrost on the Qinghai–Tibet Plateau at global and continental scales. These comparative studies will enhance our understanding of microbial functioning in degrading permafrost ecosystems and help inform effective strategies for managing and mitigating the impacts of climate change on permafrost regions.