Early Melting Research Articles

Interfacial Phenomena and Inclusion Formation at Early Melting Stages of Lanthanum Ferroalloys in a Non-Oriented Electrical Steel

Interfacial Phenomena and Inclusion Formation at Early Melting Stages of Lanthanum Ferroalloys in a Non-Oriented Electrical Steel

Effect of Cage Occupancy on Stability and Decomposition of Methane Hydrate.

Gas hydrates usually contain a certain number of empty cages that will both affect the hydrate stability and reduce the gas storage capacity. In this work, by MD simulations, we found that the hydrate stability is related to the cage occupancy, the empty cage types, and especially the distribution of empty cages. With the decrease of overall occupancy, the stability of hydrate becomes worse. Under the same overall occupancy, the more concentrated the empty cages are, the more unstable the hydrate is and hence the faster it decomposes. The methane molecules may migrate between distorted cages during the decomposition, resulting in a temporary increase in the stability of hydrate. Hydrates with different empty cage distributions show different decomposition mechanisms: when empty cages are concentrated, the melting rate is fast first due to the rapid decomposition of empty cages, but the remaining filled cages will reduce the melting rate; when empty cages are separated on the contrary, the early melting is slow because of the high local occupancy, and the following melting will be accelerated because of the high melting surface area. It indicates that the empty cage distribution plays a controlling role in hydrate decomposition kinetics at different stages.

Evolution of the Wuyi-Yunkai Orogeny Effected by Early Paleozoic Crustal Partial Melting: Insights from Zircon Grains of Fuhuling Migmatites in the Yunkai Region, South China

Evolution of the Wuyi-Yunkai Orogeny Effected by Early Paleozoic Crustal Partial Melting: Insights from Zircon Grains of Fuhuling Migmatites in the Yunkai Region, South China

CHANGE DYNAMICS OF AIR TEMPERATURE AND ATMOSPHERIC RAIN IN ALIBAY AND ZAGATALA TERRITORY OF AZERBAIJAN

Aim: the main aim of the study is exploration of change dynamics of air temperature and atmospheric rain in Alibey and Zagatala territory of Azerbaijan.In the article, the author used the data for 1961-2019 to study possible climatic changes in Alibey and Zagatala on the basis of instrumental observations, as well as studied the specifics of the timing of the distribution of key parameters. One of the most serious problems of humanity today is global climate change. Therefore, the study of the temporal temperature and sediments in the current period is one of the current tasks. Temperature fluctuations and the number of sediments directly affect the stock river and, in general, the hydrological regime. The work analyzes the periodic flow of air temperature and atmospheric sediments. Averaged monthly values of temperature and sediments for decades. Methodolgy: Data from 1961-1990 were used to calculate the "norms" based on WTO recommendations. The data of Alibey (absolute height 1540 meters) and Zagatala (absolute height 487 meters) meteorological stations of the former Hydrometeorological Committee and the current National Hydrometeorology Department were used to conduct these analyzes. Results:Calculated the mean square deviations of air temperature and determined large anomalies (1.5σ). For the considered seasons, years were found with a shortage of sediments and with abundant sediments. It has been established that in the last decade the number of positive temperature anomalies has increased. Sustaining the trend towards warming, with insignificant cooling in the last decade, as well as the absence of significant changes in the regime of sediments. It was found that the world community is seriously concerned about the number of natural disasters, huge losses caused by droughts and fires, which are the result of changes occurring in the surrounding area. It is stated that this fact testifies to the sharp trend of increasing the aridization of the territory, although the observed increase in air temperature is not accompanied by the corresponding increase in atmospheric sediments. The conclusion is that the effective means of preventing the consequences of climate change will be the creation and strengthening of the system of forecasting poverty and climatic services. Scientific novelity: The increase of air temperature is significantly to cause some early melting of the soil, resulting in an increase in water losses during spring floods

The Effect of Preheating Current on the Melting Behavior of Bolt Projection Welding of Al-Si Coated Hot-Stamped Boron Steel

This study evaluated the effect of preheating on early stage melting behavior of a Al-Si coated hot stamped boron steel bolt during projection welding. A large amount of heat was generated in the early stage of projection welding. Because of the large heat generation, a rapid collapse of the projection occurred and a molten coating layer remained on the interface of the welded part. This caused welding defects such as expulsion and porosity. However, preheating helped remove the molten Al-Si coating layer by pushing it out toward the outer edge of the molten pool. This suggests that preheating can effectively minimize or remove the molten coating layer within the weld. Preheating also prevented the rapid collapse of the projection by partially melting the projection, and thus improving the contact area. These phenomena can prevent the concentration of current density at the weld interface and hence decrease heat generation. Finally, the preheating current improved nugget quality by promoting the stable growth of the melted metal and by preventing expulsion and porosity.

Early global mantle chemical and isotope heterogeneity revealed by the komatiite-basalt record: The Western Australia connection

Although the heterogeneous nature of the chemical composition of Earth's mantle is now well established, the origin and longevity of the heterogeneities continue to be debated. In order to further study early-Earth heterogeneities, we present a set of Sm-Nd, Lu-Hf, Re-Os, and Hf-W isotope and lithophile and siderophile element abundance data for komatiites and basalts from the ∼3.53 Ga Coonterunah, ∼3.34 Ga Kelly, and ∼3.18 Ga Ruth Well and Regal systems of the Pilbara Craton in Western Australia. The Sm-Nd, Lu-Hf, and Re-Os isotope data yield isochrons consistent with the accepted emplacement ages of the respective komatiite-basalt lavas. The mantle sources evolved with long-term 147Sm/144Nd = 0.200 to 0.214 and 176Lu/177Hf = 0.0355 to 0.0395, spanning the entire range of the time-integrated Sm/Nd and Lu/Hf measured in the Archean and Proterozoic komatiite-basalt systems to-date. Unlike with the other early Archean komatiites and basalts, the coupled 143Nd-176Hf isotope systematics of the Pilbara lavas provide no evidence for the involvement of early magma ocean processes in the evolution of their mantle sources. Episodes of variable degrees of partial mantle melting and melt extraction can account for the observed large variations in the time-integrated Sm/Nd and Lu/Hf ratios in the early Archean mantle domains.In contrast to the highly variable Nd-Hf systematics, the initial γ187Os values vary within a narrow range from +0.9 to −0.4 indicating that the Pilbara mantle sources evolved with chondritic time-integrated Re/Os. The apparent discrepancy between the depletions in incompatible lithophile trace elements and near-chondritic Re/Os observed globally is reconciled via a model whereby early low-degree mantle melting events fractionated Sm from Nd and Lu from Hf, but had little effect on the Re/Os ratio. This in turn would imply early formation and long-term isolation of a basaltic crust highly enriched in incompatible lithophile trace elements.The calculated total HSE abundances in the komatiite mantle sources range from ∼30% in the Coonterunah to ∼70% in the Regal system, of those in the estimates for the modern BSE, indicative of a 2.4× increase in HSE abundances from 3.53 to 3.18 Ga.All four komatiite-basalt systems exhibit positive 182W anomalies ranging between +11.4 and +7.7 ppm. The 182W/184W compositions and calculated HSE abundances in the Pilbara komatiite-basalt sources are inversely correlated and are most consistent with grainy late accretion of large differentiated planetesimals. Regression of the combined 182W-HSE data for the komatiite systems allows an estimate of the W isotopic composition of the pre-late accretion BSE of +17 ± 7. This estimate is similar to that of the Moon of +25 ± 5 and lends further support to the notion regarding an initially common W isotopic composition in the Earth-Moon system.Regression of the available HSE abundance data for komatiite mantle sources worldwide provides an estimate for the time of complete homogenization of late accreted materials within the mantle by 2.5 ± 0.2 Ga. Calculations indicate an average survival time of late accreted planetesimals in the Earth's mantle of 1.9 ± 0.2 Ga, which constrains the average mantle stirring rates for the HSE in the Hadean and Archean.

InSAR Monitoring of Arctic Landfast Sea Ice Deformation Using L-Band ALOS-2, C-Band Radarsat-2 and Sentinel-1

Arctic amplification is accelerating changes in sea ice regimes in the Canadian Arctic with later freeze-up and earlier melt events, adversely affecting Arctic wildlife and communities that depend on the stability of sea ice conditions. To monitor both the rate and impact of such change, there is a need to accurately measure sea ice deformation, an important component for understanding ice motion and polar climate. The objective of this study is to determine the spatial-temporal pattern of deformation over landfast ice in the Arctic using time series SAR imagery. We present Interferometric Synthetic Aperture Radar (InSAR) monitoring of Arctic landfast sea ice deformation using C-band Radarsat-2, Sentinel-1 and L-band ALOS-2 in this paper. The small baseline subset (SBAS) approach was explored to process time series observations for retrieval of temporal deformation changes along a line-of-sight direction (LOS) over the winter. It was found that temporal and spatial patterns of deformation observed from different sensors were generally consistent. Horizontal and vertical deformations were also retrieved by a multi-dimensional SBAS technique using both ascending and descending Sentinel-1 observations. Results showed a horizontal deformation in the range of −95–85 cm, and vertical deformation in the range of −41–63 cm in Cambridge Bay, Nunavut, Canada during February-April 2019. High coherence over ice from C-band was maintained over a shorter time interval of acquisitions than L-band due to temporal decorrelation.

Highly refractory dunite formation at Gibbs Island and Bruce Bank, and its role in the evolution of the circum-Antarctic continent

ABSTRACT The continental margin is of profound importance as it records continental growth by accretion of orogenic magmas and following continental rifting. A high degree of mantle melting due to hydrous fluid input is expected to simultaneously stimulate continental growth and lower the intrinsic density of the mantle than more fertile mantle, which in turn isolates the continental lithosphere from the convective mantle. The mantle peridotites from Gibbs Island (South Shetland Islands) and Bruce Bank in the Drake Passage provide us an insight into the tectonic history in the circum-Antarctic region. To elucidate the continental growth of Antarctica, we present geochemical data of eight dunites from Gibbs Island and one dunite from Bruce Bank, including Re–Os isotope and highly siderophile element compositions. The dunites are severely affected by serpentinization as evidenced by antigorite + brucite or lizardite (loss on ignition = LOI ranging from 3 to 34 wt.%) but contain primary euhedral to subhedral chromites with or without spherical inclusions. The chromites rarely form lens-shaped aggregates. A dunite from Gibbs Island contains fresh olivine grains filling a fracture in the chromite with low LOI (3 wt.%), indicating a deserpentinization origin from a precursor serpentinized dunite. The dunites show highly depleted bulk-rock major element compositions (Mg/Si = 1.4–1.6 and Al/Si = 0.004–0.01 for Gibbs Island dunites, Mg/Si = 0.66 and Al/Si = 0.008 for Bruce Bank dunite), overlapping a compositional field defined by forearc peridotites. The positive correlation in Re/Ir–LOI space corroborates Re input during the later serpentinization process. The 187Os/188Os ratios of the dunites range from 0.11907 to 0.14493. Phanerozoic Re-depletion (melt depletion) ages of ca. 535–129 Ma are recorded in the Gibbs Island dunites, except for one with a Mesoproterozoic Re-depletion age of ca. 1.2 Ga. Since there exists serpentinization-related perturbation of Re, the ages provide minimum time estimates for melt depletion events. The early Paleozoic melt depletion is inferred to have occurred at a very early stage of Antarctic Peninsula formation in response to plate convergence along the margin of Gondwana, whereas the Mesoproterozoic Re-depletion age reflects convecting mantle heterogeneity unrelated to any nearby crust-forming events. The petrographic characteristics of the chromites and highly depleted nature of the dunites are attributed to melt–peridotite reaction in a subduction zone setting. A feasible interpretation for the dunite formation is that the mantle had experienced two stages of melting with the final stage occurring along the Gondwana continental margin in the subduction zone setting. Resultant highly refractory lithospheric mantle was later displaced and dispersed during the Gondwana breakup. Widespread existence of the dunite may be attributed to multi-stage melt depletion along the continental margin.

Early Cretaceous partial melting recorded by pelitic gneiss from the Nagasaki Metamorphic Complex, western Kyushu, Japan: initiation of Cretaceous high-T metamorphism at eastern margin of Eurasia

ABSTRACT We present Early Cretaceous partial melting recorded by pelitic gneiss from the Nagasaki Metamorphic Complex, western Kyushu, Japan. The existence of the partially melted rock in the complex may imply initiation of long-lived high-T metamorphism in proto-southwest Japan at Cretaceous eastern margin of Eurasia. The gneisses are composed of three garnet-bearing layers and one felsic lens, and they show mylonitic foliation. Application of Zr-in-rutile geothermometer and quartz-in-garnet Raman geobarometer for inclusion rutile and quartz in garnet provided prograde condition of 670–692°C and 1.01–1.26 GPa and peak condition of 755–769°C and 1.17–1.38 GPa. These conditions correspond to those of lower crustal depths between volcanic arc and forearc where thermal advection by wedge mantle corner flow occurs. Presence of the felsic lens whose mineral assemblage can undergo partial melting under the peak condition and presence of a crystallized melt inclusion in garnet suggest that distinct partial melting occurred during the metamorphism. The concordant U–Pb ages of metamorphic zircon rims are ranging from 131.5 ± 4.3 to 120.1 ± 3.9 Ma. The mean square weighted deviation (MSWD) of the metamorphic age was as large as 6.4, implying a significant duration of high-T condition for growth of metamorphic zircon. The obtained ages are within the period of the magmatic hiatus that has previously proposed around southwest Japan and Korean Peninsula (ca. 160–120 Ma) that is due to stop of wedge mantle corner flow by flatting of subducting slab. Our results suggest that high-T metamorphism associated with partial melting at lower crustal depths along Early Cretaceous proto-southwest Japan has already been initiated at the late stage of the hiatus (ca. 130 Ma). This may be due to slab rollback and trench retreat at eastern margin of Eurasia.

Long time-series measurements of high-frequency acoustic scattering from sea ice

Understanding relatively recent rapid changes in Arctic sea ice calls for extensive and continuous observations of the ice cover. Utilizing datasets obtained with 38, 70, and 200 kHz upward-looking transducers in the northeast Chukchi Sea, seasonal and year-to year changes in acoustic scattering were measured. Two complete annual cycles of scattering returns from the winters of 2017–2018 and 2018–2019 were analyzed. The initial effort in this research is constrained to the stable growth phase of sea ice in winter through the early melt onset the following spring. We also restricted our analysis to individual, minimally deformed ice floes to limit the variability caused by large-scale roughness. Results from this two-year analysis will be discussed along with their implications for future measurements and acoustic remote sensing of sea ice properties.

Use of stable water isotopes to identify and estimate the sources of groundwater recharge in an alluvial aquifer of Upper Jhelum Basin (UJB), western Himalayas

In the present study, we used stable water isotopes (δ18O and δD) of source waters (rain, snow, and glacier melt) and groundwater to identify and estimate the sources of recharge in alluvial aquifer(s). The stable water isotopic composition of source waters showed a significant correlation with altitude (R2=0.75). Unlike source waters, the groundwater did not show significant spatio-temporal variation. The attenuation in the isotopic signal of groundwater may be due to lag and mixing of different waters recharging from different altitudes. The results revealed that snowmelt (44±0.9% to 68±2.7%) dominantly recharges the groundwater. The glacier melt contribution to groundwater recharge (2±0.1% to 14±0.9%) in Upper Jhelum Basin (UJB), although limited to some summer and autumn months, has tremendous significance in sustaining the groundwater recharge. The early and rapid melting of winter-accumulated snow due to climatic variability may disturb the seasonal water balance that will decrease the annual groundwater recharge.

Spatial and temporal patterns of snowmelt refreezing in a Himalayan catchment

AbstractRecent progress has been made in quantifying snowmelt in the Himalaya. Although the conditions are favorable for refreezing, little is known about the spatial variability of meltwater refreezing, hindering a complete understanding of seasonal snowmelt dynamics. This study aims to improve our understanding about how refreezing varies in space and time. We simulated refreezing with the seNorge (v2.0) snow model for the Langtang catchment, Nepalese Himalaya, covering a 5-year period. Meteorological forcing data were derived from a unique elaborate network of meteorological stations and high-resolution meteorological simulations. The results show that the annual catchment average refreezing amounts to 122 mm w.e. (21% of the melt), and varies strongly in space depending on elevation and aspect. In addition, there is a seasonal altitudinal variability related to air temperature and snow depth, with most refreezing during the early melt season. Substantial intra-annual variability resulted from fluctuations in snowfall. Daily refreezing simulations decreased by 84% (annual catchment average of 19 mm w.e.) compared to hourly simulations, emphasizing the importance of using sub-daily time steps to capture melt–refreeze cycles. Climate sensitivity experiments revealed that refreezing is highly sensitive to changes in air temperature as a 2°C increase leads to a refreezing decrease of 35%.

The Tethyan Himalaya Igneous Province: Early Melting Products of the Kerguelen Mantle Plume

AbstractThe Kerguelen large igneous province (LIP) has been related to mantle plume activity since at least 120 Ma. There are some older (147–130 Ma) magmatic provinces on circum-eastern Gondwana, but the relationship between these provinces and the Kerguelen mantle plume remains controversial. Here we present petrological, geochronological, geochemical, and Sr–Nd–Hf–Pb–Os isotopic data for high-Ti mafic rocks from two localities (Cuona and Jiangzi) in the eastern Tethyan Himalaya igneous province (147–130 Ma). Zircon grains from these two localities yielded concordant weighted mean 206Pb/238U ages of 137.25 ± 0.98 Ma and 131.28 ± 0.78 Ma (2σ), respectively. The analyzed mafic rocks are enriched in high field strength elements and have positive Nb–Ta anomalies relative to Th and La, which have ocean island basalt-like characteristics. The Cuona basalts were generated by low degrees of melting (3–5 %) of garnet lherzolites (3–5 vol% garnet), and elsewhere the Jiangzi diabases were formed by relatively lower degrees of melting (1–3%) of garnet lherzolite (1–5 vol% garnet). The highly radiogenic Os and Pb isotopic compositions of the Jiangzi diabases were produced by crustal contamination, but the Cuona basalts experienced the least crustal contamination given their relatively low γOs(t), 206Pb/204Pbi, 207Pb/204Pbi, and 208Pb/204Pbi values. Major and trace element geochemical and Sr–Nd–Hf–Pb–Os isotope data for the Cuona basalts are similar to those for products of the Kerguelen mantle plume head. Together with high mantle potential temperatures (>1500 °C), this suggests that the eastern Tethyan Himalaya igneous province (147–130 Ma) was an early magmatic product of the Kerguelen plume. A mantle plume initiation model can explain the temporal and spatial evolution of the Kerguelen LIP, and pre-continental breakup played a role in the breakup of eastern Gondwana, given the >10 Myr between initial mantle plume activity (147–130 Ma) and continental breakup (132–130 Ma). Like studies of Re–Os isotopes in other LIPs, the increasing amount of crustal assimilation with distance from the plume stem can explain the variations in radiogenic Os.

Effect of Basicity on the Sulfur Precipitation and Occurrence State in Kambara Reactor Desulfurization Slag

Kambara Reactor (KR) desulfurization slag used as slag-making material for converter smelting can promote early slag melting in the initial stage and improve the efficiency of dephosphorization. However, its direct utilization as a slagging material can increase the sulfur content in molten steel since KR desulfurization slag contains 1~2.5% sulfur. Therefore, this research focuses on the effect of basicity on the precipitation behavior and occurrence state of sulfur in KR desulfurization slag in order to provide an academic reference for the subsequent removal of sulfur from slag through an oxidizing atmosphere. The solidification process of slag was simulated by the Factsage8.0. The slag samples were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM), and the amount of CaS grains was analyzed using Image-ProPlus6.0 software. The thermodynamic calculation showed that the crystallization temperature of CaS in the molten slag gradually decreased with the increase in basicity, and the CaS crystals in the molten slag mainly existed in the matrix phase and at the silicate grain boundaries. A large number of CaS grains were precipitated along the silicate grain boundary in low-basicity (R = 2.5 and 3.0) slags and fewer CaS grains were precipitated along the silicate grain boundary, while the CaS grain density in the matrix phase was higher in the high-basicity (R = 3.5, 4.0, 4.5) slag. With the increase in basicity, the number of CaS grains gradually decreased, and the CaS grain sizes in slag sample increased gradually. The sulfur in the synthetic slag was in the form of CaS crystals and the amorphous phase, and the content of amorphous sulfur gradually increased with increasing basicity.

Pore-scale analysis on selection of composite phase change materials for photovoltaic thermal management

Composite Phase Change Materials (CPCMs) using metal foam as core material are highly promising for thermal management of photovoltaics. Selecting a proper CPCM for a given application is challenging. To address this, we developed a pore-scale lattice Boltzmann model based on X-ray micro-Computed Tomography to describe the complicated microstructures of the metal foam and computed the dynamic temperature and flow fields in representative applications. Two important parameters for the design of PCMs, melting temperature and latent heat, are discussed in this work by comparing the melting fraction, energy density, and power density for different CPCMs. Further, we demonstrate a CPCM choice for thermal management of a tilted photovoltaic panel. By comparing the thermal behavior of four different paraffin based CPCMs having similar thermophysical properties but different melting temperatures and latent heats, the effects of melting temperature and latent heat are illustrated for a practical application. Compared with the highest latent heat (Stefan number Ste = 0.1), energy density is reduced by 31.8%, 52.0%, and 63.5% for the other three cases with Ste of 0.15, 0.22, and 0.3, respectively, while the melting time is extended, with the reverse order. Besides, a lower melting temperature leads to a quicker response at the early melting stage, while this quick response is short-lived. Thus, the choice of melting temperature should balance the benefits of excellent initial thermal control against the risks of loss of control later. The results of this work help establish an effective strategy toward material selection of CPCMs.

Using the Sun to monitor Earth's melting ice sheets

Using the Sun to monitor Earth's melting ice sheets

Surges of Harald Moltke Bræ, north-western Greenland: seasonal modulation and initiation at the terminus

Abstract. Harald Moltke Bræ, a marine-terminating glacier in north-western Greenland, shows episodic surges. A recent surge from 2013 to 2019 lasted significantly longer (6 years) than previously observed surges (2–4 years) and exhibits a pronounced seasonality with flow velocities varying by 1 order of magnitude (between about 0.5 and 10 m d−1) in the course of a year. During this 6-year period, the seasonal velocity always peaked in the early melt season and decreased abruptly when meltwater runoff was maximum. Our data suggest that the seasonality has been similar during previous surges. Furthermore, the analysis of satellite images and digital elevation models shows that the surge from 2013 to 2019 was preceded by a rapid frontal retreat and a pronounced thinning at the glacier front (30 m within 3 years). We discuss possible causal mechanisms of the seasonally modulated surge behaviour by examining various system-inherent factors (e.g. glacier geometry) and external factors (e.g. surface mass balance). The seasonality may be caused by a transition of an inefficient subglacial system to an efficient one, as known for many glaciers in Greenland. The patterns of flow velocity and ice thickness variations indicate that the surges are initiated at the terminus and develop through an up-glacier propagation of ice flow acceleration. Possibly, this is facilitated by a simultaneous up-glacier spreading of surface crevasses and weakening of subglacial till. Once a large part of the ablation zone has accelerated, conditions may favour substantial seasonal flow acceleration through seasonally changing meltwater availability. Thus, the seasonal amplitude remains high for 2 or more years until the fast ice flow has flattened the ice surface and the glacier stabilizes again.

Hydrological and catchment controls on event‐scale dissolved organic carbon dynamics in boreal headwater streams

AbstractHydrological events transport large proportions of annual or seasonal dissolved organic carbon (DOC) loads from catchments to streams. The timing, magnitude and intensity of these events are very sensitive to changes in temperature and precipitation patterns, particularly across the boreal region where snowpacks are declining and summer droughts are increasing. It is important to understand how landscape characteristics modulate event‐scale DOC dynamics in order to scale up predictions from sites across regions, and to understand how climatic changes will influence DOC dynamics across the boreal forest. The goal of this study was to assess variability in DOC concentrations in boreal headwater streams across catchments with varying physiographic characteristics (e.g., size, proportion of wetland) during a range of hydrological events (e.g., spring snowmelt, summer/fall storm events). From 2016 to 2017, continuous discharge and sub‐daily chemistry grab samples were collected from three adjacent study catchments located at the International Institute for Sustainable Development‐Experimental Lakes Area in northwestern Ontario, Canada. Catchment differences were more apparent in summer and fall events and less apparent during early spring melt events. Hysteresis analysis suggested that DOC sources were proximal to the stream for all events at a catchment dominated by a large wetland near the outlet, but distal from the stream at the catchments that lacked significant wetland coverage during the summer and fall. Wetland coverage also influenced responses of DOC export to antecedent moisture; at the wetland‐dominated catchment, there were consistent negative relationships between DOC concentrations and antecedent moisture, while at the catchments without large wetlands, the relationships were positive or not significant. These results emphasize the utility of sub‐daily sampling for inferring catchment DOC transport processes, and the importance of considering catchment‐specific factors when predicting event‐scale DOC behaviour.

Silurian to early Permian slab melting and crustal growth in the southern Altaids: insights from adakites and associated mineral deposits in the Dananhu arc, Eastern Tianshan, NW China

Silurian to early Permian slab melting and crustal growth in the southern Altaids: insights from adakites and associated mineral deposits in the Dananhu arc, Eastern Tianshan, NW China

Precipitation influence on and response to early and late Arctic sea ice melt onset during melt season

AbstractThe region containing portions of the East Siberian Sea and Laptev Sea (73°–84°N, 90°–155°E) is the area of focus (AOF) for this study. The impacts of precipitation, latent heat (LH) and sensible heat (SH) fluxes on sea ice melt onset in the AOF are investigated. Four early melting years (1990, 2012, 2003, and 1991) and four late melting years (1982, 1983, 1984, and 1996) are compared to better identify the different responses to melt onset timing. A consistency check is performed between multiple Arctic precipitation products (including NASA MERRA‐2, ECMWF ERA‐Interim [ERA‐I], and ECMWF ERA5 reanalyses as well as GPCP V2.3 observations) since there is not yet a high‐quality ground‐truth Arctic precipitation data product. MERRA‐2 has the greatest monthly average precipitation, snowfall, evaporation, and net LH flux. ERA‐I suggests that liquid precipitation starts earlier in the year than MERRA‐2 and ERA5, while GPCP shows different seasonal precipitation variations from the reanalyses. MERRA‐2 has the clearest and most amplified seasonal trends for the parameters used in this study, so the daily time series and anomalies of MERRA‐2 variables before and after the first major melt event are investigated. ERA5 is used to check these results because ERA‐I and ERA5 display similar seasonal trends. According to MERRA‐2, during early melt years, surface SH flux loss and precipitation are above average in the days before and after the first major melt event. During late melt years, surface SH flux loss and precipitation are below average in the month leading up to the first major melt event.