Late Melt Research Articles

Charging performance of a novel finned latent heat storage unit under sloshing

Latent heat storage (LHS) on ships using phase change materials (PCMs) is challenged by inefficient heat storage efficiency and susceptibility to sloshing conditions. To address this issue, this paper proposes a shell-and-tube LHS unit using innovative fins. The enthalpy-porosity approach is employed to study the melting characteristics of LHS units under sloshing, focusing on the effects of direction, frequency, and strength of sloshing conditions. An optimal fin configuration to enhance thermal storage performance under sloshing is proposed. The results indicate that the sloshing conditions effectively enhance the temperature uniformity and heat storage capacity of LHS units. Compared with the slosh-free condition, the full melting duration of PCMs in LHS units under roll and heave conditions is reduced by 20.9 % and 23.6 %, respectively. Moreover, the natural convection intensity and heat transfer uniformity under sloshing conditions increase significantly, improving the heat transport capacity in the late melting stage. Additionally, the heat storage capacity of LHS units improves with a decrease in sloshing frequency and an increase in sloshing strength; however, there is a limit to the performance enhancement gains. Interestingly, the arrangement of fins closest to the refractory zone effectively improves the heat transport in the later melting stage, resulting in a further 6.8% increase in the melting rate.

A dunite fragment in meteorite Northwest Africa (NWA) 11421: A piece of the Moon’s mantle

Abstract A centimeter-sized fragment of dunite, the first recognized fragment of Moon mantle material, has been discovered in the lunar highlands breccia meteorite Northwest Africa (NWA) 11421. The dunite consists of 95% olivine (Fo83), with low-Ca and high-Ca pyroxenes, plagioclase, and chrome spinel. Mineral compositions vary little across the clast and are consistent with chemical equilibration. Mineral thermobarometry implies that the dunite equilibrated at 980 ± 20 °C and 0.4 ± 0.1 gigapascal (GPa) pressure. The pressure at the base of the Moon’s crust (density 2550 kg/m3) is 0.14–0.18 GPa, so the dunite equilibrated well into the Moon’s upper mantle. Assuming a mantle density of 3400 kg/m3, the dunite equilibrated at a depth of 88 ± 22 km. Its temperature and depth of equilibration are consistent with the calculated present-day selenotherm (i.e., lunar geotherm). The dunite’s composition, calculated from mineral analyses and proportions, contains less Al, Ti, etc., than chondritic material, implying that it is of a differentiated mantle (including cumulates from a lunar magma ocean). The absence of phases containing P, Zr, etc., suggests minimal involvement of a KREEP component, and the low proportion of Ti suggests minimal interaction with late melt fractionates from a lunar magma ocean. The Mg/Fe ratio of the dunite (Fo83) is significantly lower than models of an overturned unmixed mantle would suggest, but is consistent with estimates of the bulk composition of the Moon’s mantle.

Geochemical significance of lithium and boron isotopic heterogeneity evolving during the crystallization of granitic melts

Abstract We present Li and B isotope data for muscovite, biotite, and feldspar + quartz separated from two-mica granite and biotite granite samples from the Huayang-Wulong granite suite (south Qinling, central China). Our data demonstrate systematic differences in the Li and B isotopic compositions among these minerals. Our results indicate that early-crystallizing minerals have lower δ7Li and δ11B values than the original melt and that residual melts and late magmatic fluids may acquire anomalously high δ7Li and δ11B values. Furthermore, our data imply that (1) late melts and magmatic fluids do not reflect the composition of their source melt, (2) minerals that crystallized over a large segment of magma evolution may be isotopically zoned, and (3) mineral-selective alteration by late magmatic fluids camouflages the source of the fluid, whose δ7Li and δ11B values reflect the isotopic compositions of the altered minerals rather than the composition of the remaining rock.

Temporal dynamics in alpine snowpatch plants along a snowmelt gradient explained by functional traits and strategies.

Alpine snowpatches are characterised by persistent snow cover, short growing seasons and periglacial processes, which has resulted in highly specialised plant communities. Hence, these snowpatch communities are among the most threatened from climate change. However, temporal dynamics in snowpatch microclimate and plant composition are rarely explored, especially in the marginal alpine environments of Australia. Seven snowpatches were categorised into early, mid and late snowmelt zones based on growing season length, with soil temperatures recorded from 2003 to 2020 and plant composition surveyed in 84 1m2 quadrats in 2007, 2013 and 2020. Microclimate, species diversity, plant cover and composition, along with community-weighted trait means and plant strategies were assessed to understand snowpatch dynamics in response to climate change. We found that growing season length and temperatures have increased in late melt zones, while changes were less consistent in early and mid melt zones. There were few changes in species diversity, but increases in graminoids and declines in snowpatch specialists in mid and late melt zones. Community-weighted plant height, leaf area and leaf weight also increased, particularly in mid and late melt zones, while plant strategies shifted from compositions of ruderal-tolerant to stress-tolerant. Here, we show that snowpatch communities are rapidly changing in response to longer growing seasons and warmer temperatures, with the greatest changes occurring where snow persists the longest. The results highlight the climate-induced loss of defining biotic and abiotic characteristics of snowpatches, as temporal convergence of compositions along snowmelt gradients threatens the distinctiveness of snowpatch plant communities.

Study on the thermal storage performance of a new cascade structure phase change thermal storage tank

Due to the intermittent and fluctuating nature of solar energy, phase change thermal storage technology plays a crucial role in the field of solar thermal energy utilization. As a current research hotspot, the organic combination of a cascade setup and a thermal storage tank can significantly improve the performance of thermal storage. To this end, a new physical model of cascaded phase change thermal storage has been designed, and a corresponding numerical model of three-dimensional unsteady states has been established based on the conventional cascade structure. The equations were solved using the finite-difference method and the phase change material (PCM) melting process was simulated using MATLAB based on C language numerical programming and the simulation results were compared with literature for validation. The effects on the liquid phase fraction and heat storage capacity of the cascaded phase change storage tank were investigated for each level of PCM arrangement, the height-to-diameter ratio of the storage tank and the inlet temperature of the heat transfer fluid. The results show that compared to conventional cascade thermal storage tanks, the new cascade phase change thermal storage tank can decrease the thermal storage time by 33 % and increase the thermal storage rate by 42 %, optimizing the disadvantages of the conventional structure which significantly reduces the heat transfer rate in the late melting stage. When the arrangement of PCM in the tank is modified, the melting time is shorter for the solution that arranges the PCM in the order of decreasing melting temperature as the distance from the heat exchanger wall or from the inlet increases, and the complete melting time of the PCM is reduced by 28 % and 30 % respectively compared to other solutions, and the heat storage rate is increased by 35 % and 37 % respectively. The larger the height-to-diameter ratio, the faster the rate of heat transfer from the heat exchange pipe to the outermost side of the tank, resulting in a 19 % and 45 % increase in heat storage rate for the height-to-diameter ratio of 5.92 compared to 5.00 and 4.12, respectively. When the inlet temperature is increased from 85 °C to 95 °C, the melting rate is increased by 32 % due to the increased heat transfer temperature difference. The results presented in this paper can provide some theoretical reference for the optimal design of cascade phase change thermal storage units, etc.

Generation of crystal-poor rhyolites from a shallow plutonic reservoir in the Famatinian arc (Argentina)

The Ordovician rocks of Sierra Las Planchadas are an exceptionally preserved natural example of a plutonic-volcanic connection. Located in northwestern Argentina, the Las Planchadas Formation consists of a monzogranitic batholith that displays a window into the source of large subvolcanic rhyolitic rocks, cryptodomes and volcanic feeder-dykes. Mafic intrusions and felsic dykes occur cutting the plutonic rocks. Grain-scale relationships, whole-rock compositions and mineral chemistry indicate that monzogranites and rhyolites are two comagmatic members which differentiated within upper crust magma reservoirs. Monzogranites accumulated some plagioclase and trapped a large volume of melt, denoted by a high modal percentage (~64–71%) of near-solidus minerals, comprised of alkali feldspar, albite-rich plagioclase (An<30), and late crystallized quartz. The formation of felsic dykes and rhyolitic cryptodomes is the result of a late melt extraction stage facilitated by the injection of hot mafic magmas from deeper in the system. The mafic-induced thermal reactivation increased the amount of melt-filled pore stored within a highly-crystallized monzogranite reservoir. The breakdown of the low-temperature phases overpressurized the mush and opened a network of microfractures into which residual melts, depleted in feldspar-compatible trace elements (Ba, Sr, and Eu), infiltrated. The draining system involved thin interconnected vein-like channels that merged into wider sheet-like conduits. Our results suggest that channelized segregation of late-stage melts in the subvolcanic environment is a mechanism for triggering rhyolitic eruptions.

The first main group ureilite with primary plagioclase: A missing link in the differentiation of the ureilite parent body

AbstractMS‐MU‐012, a 15.5 g clast from the Almahata Sitta polymict ureilite, is the first known plagioclase‐bearing main group ureilite. It is a coarse‐grained (up to 4 mm), equilibrated assemblage of 52% olivine (Fo 88), 13% orthopyroxene (Mg# 89.2, Wo 4.5), 11% augite (Mg# 90.2, Wo 37.3), and 14% plagioclase (An 68), plus minor metal and sulfide. The plagioclase grains have been secondarily remelted and internally recrystallized, but retain primary external morphologies. Melt inclusions occur in olivine. Rounded chadocrysts of olivine and orthopyroxene are enclosed in augite grains. In terms of texture, mineralogy, major and minor element mineral compositions, and oxygen isotopes, MS‐MU‐012 is virtually identical to the archetypal Hughes‐type main group ureilites, with the significant addition of primary plagioclase. We conclude that MS‐MU‐012 formed as a cumulate in a common lithologic unit with the Hughes‐type ureilites. Based on reconstructed compositions of melts trapped in olivine, orthopyroxene, and augite in the Hughes‐type samples, we infer that the parent magma of the Hughes unit originated as a late melt in the incremental melting of the ureilite parent body (UPB), near the end of the melting sequence, but was not completely extracted from the mantle like earlier melts and was emplaced in an intrusive body. MELTS calculations indicate that olivine began to crystallize at ~1260 °C, followed shortly thereafter by co‐crystallization of orthopyroxene and augite. Plagioclase began to crystallize at ~1170–1180 °C. Graphite was buoyant in the melt and became heterogeneously distributed in flotation cumulates. Residual silicate liquid was extracted from the cumulate pile and could have crystallized to form the “labradoritic melt lithology” (with plagioclase of An ~68‐35), which is partially preserved as clasts in polymict ureilites. The final equilibration temperature recorded by the Hughes unit was ~1140–1170 °C, just before catastrophic disruption of the UPB. MS‐MU‐012 provides a critical missing link in the differentiation history of this asteroid.

A floating remote observation system (FROS) for full seasonal lake ice evolution studies

A floating remote observation system (FROS) was designed to investigate the full seasonal evolution of lake ice. FROS operates effectively in open water and ice. It can automatically measure meteorological data, such as the air temperature and solar radiation, as well as ice/snow data, including ice thickness and snow depth. These observations help to fill the current knowledge gap of lake ice observations during the early freezing and late melting periods because of the limited bearing capacity of ice cover. A mid-latitude lake was selected for field experiments to verify the effectiveness of FROS, where the duration of the survey was 101 days, of which 97 were during an ice-covered period. The results reveal that the lake ice went through a fast freezing period, equilibrium period, and a melting period, with a maximum ice thickness of 35.5 cm. The ice melting rate was 1.7 cm/day, which was approximately double the ice growth rate of 0.7 cm/day during the fast freezing period. FROS was able to record the complete evolution of lake ice and of different meteorological elements, with good stability in both open water and frozen conditions, and can accommodate wind speeds up to 6.4 m/s. Meanwhile, FROS has good versatility, and other measurement instruments such as chlorophyll and dissolved oxygen sensors, longwave radiometers, and conductivity sensors can be added to it. The application of FROS will be important for calculations of the thermal balance of snow and ice, and studies of the annual and seasonal evolution of ecological characteristics in frozen lakes.

Experimental and numerical studies on the heat transfer improvement of a latent heat storage unit using gradient tree-shaped fins

To improve the thermal performance of horizontal latent heat storage (LHS) units, this study investigates two innovative LHS units using uniform and gradient tree-shaped fins. By coupling visualization experiments and three-dimensional numerical simulations, the melting/solidification behavior and thermal properties of innovative LHS units are comprehensively analyzed and compared with traditional LHS units. The results show that tree-shaped fins facilitate heat diffusion from point to area, breaking the heat transport hysteresis in traditional LHS units, thus accelerating the melting/solidification rate. During the melting process, the gradient tree-shaped fins strengthen the heat transfer in lower parts of the LHS unit and extend the convective heat transfer duration in upper regions, promoting the synergistic strengthening of natural convection and heat conduction in the late melting stage. Compared to the uniform fin layout, the gradient tree-shaped fins effectively increase the melting rate, shortens the melting duration by 9%, and further improve the overall temperature uniformity of LHS units. However, the non-uniform transport path of gradient tree-shaped fins is not conducive to solidification heat transfer with conduction as the primary thermal regime, which increases the temperature gradient of LHS units and prolongs the solidification duration by 57.4% compared to the uniform tree-shaped fins.

Numerical study on the thermal enhancement of horizontal latent heat storage units with hierarchical fins

The poor thermal performance of shell and tube latent heat storage (LHS) units using phase change materials restricts large-scale renewable energy utilisation. To address this issue, an innovative hierarchical fin is designed here to improve the charging performance of horizontal LHS units. The charging characteristics of innovative LHS units are explored and compared with available LHS units by a numerical model using the enthalpy-porosity scheme. Moreover, the response surface method (RSM) is applied to optimise the hierarchical fin by maximising its charging rate. The results indicate that hierarchical fins significantly improve the charging rate and temperature uniformity of horizontal LHS units. Except for the early heat conduction stage, melting convection develops as the dominant mode in the middle stage but decays in the later stage. Compared to tree-shaped fins, the hierarchical fin dramatically enhances heat conduction performance in the late melting stage, leading to a maximum reduction of 41.1% in the whole melting time of horizontal LHS units. To maximise the charging performance, the RSM results suggest the thickness gradient of the primary bifurcation, thickness fractal dimension, and length ratio of hierarchical fins should be 3.98, 1.34, and 1.11, respectively, providing constructive guidance for engineering applications of horizontal LHS units.

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.

Arctic sea ice melt onset favored by an atmospheric pressure pattern reminiscent of the North American-Eurasian Arctic pattern

The timing of melt onset in the Arctic plays a key role in the evolution of sea ice throughout Spring, Summer and Autumn. A major catalyst of early melt onset is increased downwelling longwave radiation, associated with increased levels of moisture in the atmosphere. Determining the atmospheric moisture pathways that are tied to increased downwelling longwave radiation and melt onset is therefore of keen interest. We employed Self Organizing Maps (SOM) on the daily sea level pressure for the period 1979–2018 over the Arctic during the melt season (April–July) and identified distinct circulation patterns. Melt onset dates were mapped on to these SOM patterns. The dominant moisture transport to much of the Arctic is enabled by a broad low pressure region stretching over Siberia and a high pressure over northern North America and Greenland. This configuration, which is reminiscent of the North American-Eurasian Arctic dipole pattern, funnels moisture from lower latitudes and through the Bering and Chukchi Seas. Other leading patterns are variations of this which transport moisture from North America and the Atlantic to the Central Arctic and Canadian Arctic Archipelago. Our analysis further indicates that most of the early and late melt onset timings in the Arctic are strongly related to the strong and weak emergence of these preferred circulation patterns, respectively.

Timescales of Partial Melting and Melt Crystallization in the Eastern Himalayan Orogen: Insights From Zircon Petrochronology

AbstractRevealing the timescales of metamorphic and anatectic processes is central to our understanding of tectonic evolution of collisional orogens. High‐temperature migmatites and leucogranites are well exposed in the Himalayan orogenic core, making it an ideal region to study the timing and duration of partial melting and melt crystallization of the orogen. Here, we report an integrated and comprehensive data set of petrography, U‐Pb age, and trace element data for zircon from a pelitic granulite and associated leucosomes of the Greater Himalayan Sequence (GHS) in the Yadong area, eastern Himalaya. Zircon grains with complex internal structure retain variable ages ranging from 32 Ma to 13 Ma that correlate systematically with changes in the concentrations of Y, Th, U, Hf, Nb, Ta, and HREE, and ratios of Th/U, Eu/Eu*, and Nb/Ta. Combined with petrologic analysis, we conclude that the granulite witnessed high‐temperature metamorphism, melting, and melt crystallization over ∼20 Myr. Prograde, simultaneous increases in pressure and temperature and associated dehydration melting began at least by ∼32 Ma and lasted until ∼24 Ma. Subsequent quasi‐isothermal decompression‐melting occurred between ∼22 and 19 Ma, and late melt crystallization spanned ∼19 to 13 Ma. Large volumes of melt generated during prograde metamorphism could have triggered exhumation of GHS rocks, increasing melt fraction through a positive feedback between exhumation and melting. More comprehensive analysis of different rock types led to more complete and different interpretations for the timing of exhumation and melt crystallization in the Yadong‐Sikkim region and might enable alternate interpretations elsewhere in the Himalayas.

Terrestrial Inputs Shape Coastal Bacterial and Archaeal Communities in a High Arctic Fjord (Isfjorden, Svalbard).

The Arctic is experiencing dramatic changes including increases in precipitation, glacial melt, and permafrost thaw, resulting in increasing freshwater runoff to coastal waters. During the melt season, terrestrial runoff delivers carbon- and nutrient-rich freshwater to Arctic coastal waters, with unknown consequences for the microbial communities that play a key role in determining the cycling and fate of terrestrial matter at the land-ocean interface. To determine the impacts of runoff on coastal microbial (bacteria and archaea) communities, we investigated changes in pelagic microbial community structure between the early (June) and late (August) melt season in 2018 in the Isfjorden system (Svalbard). Amplicon sequences of the 16S rRNA gene were generated from water column, river and sediment samples collected in Isfjorden along fjord transects from shallow river estuaries and glacier fronts to the outer fjord. Community shifts were investigated in relation to environmental gradients, and compared to river and marine sediment microbial communities. We identified strong temporal and spatial reorganizations in the structure and composition of microbial communities during the summer months in relation to environmental conditions. Microbial diversity patterns highlighted a reorganization from rich communities in June toward more even and less rich communities in August. In June, waters enriched in dissolved organic carbon (DOC) provided a niche for copiotrophic taxa including Sulfitobacter and Octadecabacter. In August, lower DOC concentrations and Atlantic water inflow coincided with a shift toward more cosmopolitan taxa usually associated with summer stratified periods (e.g., SAR11 Clade Ia), and prevalent oligotrophic marine clades (OM60, SAR92). Higher riverine inputs of dissolved inorganic nutrients and suspended particulate matter also contributed to spatial reorganizations of communities in August. Sentinel taxa of this late summer fjord environment included taxa from the class Verrucomicrobiae (Roseibacillus, Luteolibacter), potentially indicative of a higher fraction of particle-attached bacteria. This study highlights the ecological relevance of terrestrial runoff for Arctic coastal microbial communities and how its impacts on biogeochemical conditions may make these communities susceptible to climate change.

Quantification of seasonal and diurnal dynamics of subglacial channels using seismic observations on an Alpine glacier

Abstract. Water flowing below glaciers exerts a major control on glacier basal sliding. However, our knowledge of the physics of subglacial hydrology and its link with sliding is limited because of lacking observations. Here we use a 2-year-long dataset made of on-ice-measured seismic and in situ-measured glacier basal sliding speed on Glacier d'Argentière (French Alps) to investigate the physics of subglacial channels and its potential link with glacier basal sliding. Using dedicated theory and concomitant measurements of water discharge, we quantify temporal changes in channels' hydraulic radius and hydraulic pressure gradient. At seasonal timescales we find that hydraulic radius and hydraulic pressure gradient respectively exhibit a 2- and 6-fold increase from spring to summer, followed by comparable decrease towards autumn. At low discharge during the early and late melt season channels respond to changes in discharge mainly through changes in hydraulic radius, a regime that is consistent with predictions of channels' behaviour at equilibrium. In contrast, at high discharge and high short-term water-supply variability (summertime), channels undergo strong changes in hydraulic pressure gradient, a behaviour that is consistent with channels behaving out of equilibrium. This out-of-equilibrium regime is further supported by observations at the diurnal scale, which prove that channels pressurize in the morning and depressurize in the afternoon. During summer we also observe high and sustained basal sliding speed, which supports that the widespread inefficient drainage system (cavities) is likely pressurized concomitantly with the channel system. We propose that pressurized channels help sustain high pressure in cavities (and therefore high glacier sliding speed) through an efficient hydraulic connection between the two systems. The present findings provide an essential basis for testing the physics represented in subglacial hydrology and glacier sliding models.

Isotopic and geochemical features of the genesis of igneous complexes and ore-magmatic systems in the Chukotka sector of the Russian Arctic coast

Research subject. The isotopic composition (Pb-Pb, Sm-Nd, Rb-Sr, Os/Os, Hf/Hf, 3 He/4 He, etc.) of magmatic complexes and ore-magmatic systems (OMS) of two ore clusters (Kupolsky and Ilirneysky) located in the subpolar Western Chukotka was studied. These ore clusters differ from each other both in their structural position and the age of their magmatic complexes, within which the largest deposits of Au-Ag type are known. Materials and methods. The Pb-Pb, Rb-Sr, SmNd, Re-Os, Lu-Hf, 3 He/4 He, 40Ar/36Ar and sulphur isotopic systems were studied at the VSEGEI centre for isotopic studies (St. Petersburg), as well as at the Institute of Geology, Geochemistry and Ore Deposits (IGEM, Moscow) and the Laboratory of Stable Isotopes of the Far Eastern Geological Institute (FEGI, Vladivostok). Re and Os were measured using an ELEMENT-2 inductively coupled plasma single-collector mass spectrometer. Sulphur isotopic ratios were measured using a Finnigan MAT 253 isotope mass spectrometer. Results and conclusions. On the basis of the isotope-geochemical data obtained, an assumption was made that various deep sources participated in the magma generation, and the differentiated composition of late melts may reflect the melting processes of the crust upper horizons. When comparing the data on the magmatism of the Ilirneysky and Kupolsky ore clusters, a different degree of crustal rock influence on melt generation was revealed. The Kupolsky ore cluster is characterised by a large influence of mantle sources in intraplate magmatism associated with ore formation processes. This is likely to have determined a greater amount of mineralisation in the Kupolsky cluster compared to the Ilirneysky ore cluster.

An ecosystem-wide reproductive failure with more snow in the Arctic.

2018: Arctic researchers have just witnessed another extreme summer—but in a new sense of the word. Although public interest has long been focused on general warming trends and trends towards a lower sea ice cover in the Arctic Ocean, this summer saw the realization of another predicted trend: that of increasing precipitation during the winter months and of increased year-to-year variability. In a well-studied ecosystem in Northeast Greenland, this resulted in the most complete reproductive failure encountered in the terrestrial ecosystem during more than two decades of monitoring: only a few animals and plants were able to reproduce because of abundant and late melting snow. These observations, we suggest, should open our eyes to potentially drastic consequences of predicted changes in both the mean and the variability of arctic climate.

Holocene environmental changes in the Northern Khibiny mountains (Kola Peninsula) inferred by diatom analysis of lake sediments

The article presents the results of diatom analysis of bottom sediment cores of Lake Shchuchye located in the northern part of the Khibiny Mountains. Data of radiocarbon dating of lacustrine sediments and comparison with previously published sections of lake sediments in the Kola Peninsula suggest that the accumulation of sediments in Shchuchye Lake began during the final stages of deglaciation in the early Holocene and continued uninterruptedly until the present time. Changes in the composition of diatom associations in sediments reflect alterations in the hydrodynamic regime of the lake associated with the isolation from the Goltsovoye Lake, influence of Kunyok River runoff, evolution of vegetation and weathering processes in the catchment area. We used concentration, variety and composition of species and distinguished 8 separate zones of diatoms. Climate changes in the Holocene are reflected directly in the change of the percentage of indicator species, and indirectly through changes in pH, etc. The early Holocene rise of temperature began in this region later than in the sea coastal area. It may reflect the pecularities of deglaciation, namely — late melting of alpine glaciers. Along with the evolutionary environmental changes some catastrophic events are reflected in the sediments of the Shchuchye Lake. For example, in early stages, there the yield of big quantity of terrigenous deposits into the lake was revealed produced by mud flows and erosion from slopes covered by scarce vegetation at that time. Mudflow processes probably led to the formation of a clear interlayer of terrigenous material in the biogenic sediments in the upper part of the section.

The importance of capturing late melt season sea ice conditions for modeling the western Arctic ocean boundary layer

To better understand the response of the western Arctic upper ocean to late summer ice-ocean interactions, a range of surface, interior, and basal sea ice conditions were simulated in a 1-D turbulent boundary layer model. In-ice and under-ice autonomous observations from the 2014 Marginal Ice Zone Experiment provided a complete characterization of the late melt-season sea ice and were used to set initial conditions, update boundary conditions, and conduct model validation studies. Results show that underestimates of open water and melt pond fraction at the sea ice surface had the largest influence on ocean-to-ice turbulent heat fluxes reducing basal melt rates by as much as 32%. This substantial reduction in latent heat loss was attributed to underestimates of open water areas and the exclusion of melt ponds by low-resolution synthetic aperture radar imagery. However, the greatest overall effect on the ice-ocean boundary layer came from mischaracterizations of basal roughness, with smooth ice scenarios resulting in 7 m of summer halocline shoaling and preservation of the near-surface temperature maximum. Rough ice conditions showed a 23% deepening of the mixed layer and erosion of heat storage above 40 m. Adjustments of conductive heat fluxes had little effect on the near-interface heat budget due to small internal thermal gradients within the late summer sea ice. Results from the 1-D boundary layer simulations highlight the most influential components of sea ice structure during late summer conditions and provide the magnitude of errors expected when ice conditions are mischaracterized.

Colorectal cancer susceptibility genetic variants in tumor free and colorectal carcinoma bearing Hungarian population. Individual predisposition to cancer

Genome-wide association studies (GWAS) using population-based designs have identified many genetic loci, at which common variants can influence the risk of developing the sporadic colon cancers. These are single nucleotide polymorphisms (SNPs) located on different chromosomes, close to genes involved in cancer developing process, and the SNPs modify their functions, and as a consequence the cancer risk is increased. Our aim was to provide frequency distributions data of variable (risk) allele of six independent SNPs in patients with colorectal cancers and in control Hungarian population, predicting the increased risk effect of sequence variant of SNPs. We also investigated the frequency distribution of tumor localization between right or left half of large bowel as well as the RAS mutation status. 47 non-tumorous patients and 47 patients with colorectal cancer were given oral mucosa cells or blood samples for SNP analysis. After DNA isolation, an LC480 (Roche) type PCR instrument, asymmetric LATE PCR method and melting point analysis were used for detection of sequence variations, by the assistance of two SNP specific primers, unlabeled specific probe and intercalating fluorescent dye. Genomic frequency distribution of variable alleles of SNPs predisposed to tumor development have been investigated in colorectal cancer carrier patients and the results have been compared with the same allele frequency distribution data obtained from the non-tumorous control patients and from CEU population stored in SNPnexus data base. The homozygous risk alleles of SNPs showed a 1.5-2.3-time increase in colorectal cancer carrier patients then in control and CEU patients, but the heterozygous risk allele distribution was identical in tumorous and control population. The frequency distribution of homozygous risk alleles of six SNPs was also investigated in the same time and some patients. Among 47 patients with colorectal cancer, in 3 patients carrying 3 SNPs with homozygous risk alleles, in additional 5 tumor samples two and 24 samples contain only one SNP's homozygous risk alleles, and in 15 patients, SNPs with homozygous risk alleles do not occur. In 47 control patients, only 3 samples contain two SNPs with homozygous risk alleles and 17 samples contain only one SNP with homozygous risk alleles. Significant differences of the tumorous and the control population can be seen detected. NRAS mutation was not found. Our results showed a real increased risk effect of several newly recognized low-penetrance colorectal cancer susceptibility genetic variants by influence of the regulation of neighboring genes, however, the degree of cancer risk is individual, and influenced by others environmental factors, such as dietary factors. Orv Hetil. 2018; 159(40): 1614-1623.