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1.
Sci Total Environ ; 806(Pt 1): 150530, 2022 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-34844325

RESUMEN

Sediment has been considered as an important sink for microplastics (MPs), but there are limited reports about the spatial and temporal variability of MPs in sediment from the Arctic Ocean. Furthermore, understanding is lacking on the correlation between Arctic sea ice variation and MP abundance in sediment. This study aimed to assess the MP contamination in the sediment from the Chukchi Sea over five years through three voyages (in 2016, 2018, and 2020). The MP abundances in the sediments from the Chukchi Plateau and Chukchi Shelf over five years ranged from 33.66 ± 15.08 to 104.54 ± 28.07 items kg-1 dry weight (DW) and 20.63 ± 6.71 to 55.64 ± 22.61 items kg-1 DW, respectively. The MP levels from the Chukchi Sea were lower than those from the Eastern Arctic Ocean. Our findings suggest that the Chukchi Plateau is an accumulation zone for fibers related to fishing gear and textiles under the dual influence of the Pacific and Atlantic Ocean currents. However, the reduction of these fibers in the sediment from the Chukchi Shelf might be related to bottom currents, sediment resuspension, and biomass. Moreover, the MP abundance in the sediment from the Chukchi Sea was positively correlated with the reduction of Arctic sea ice, suggesting that the melting sea ice contributes to the increase in MP levels in the sediment. The increase in blue MPs from the Chukchi Plateau over time might be attributed to melting sea ice or intense fishing activity, whereas the increase of the smallest MPs in this region could be owing to the breakdown of larger plastics during long-distance transport or the easier settlement of smaller MPs. Further time-series investigations are urgently required to improve the understanding of the environmental fate and transport of MPs among the different Arctic environmental compartments.


Asunto(s)
Microplásticos , Contaminantes Químicos del Agua , Regiones Árticas , Monitoreo del Ambiente , Cubierta de Hielo , Plásticos , Contaminantes Químicos del Agua/análisis
2.
Sci Total Environ ; 806(Pt 1): 150442, 2022 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-34563910

RESUMEN

Glacial lakes in the Himalayas are widely distributed. Since 1900, more than 100 glacial lake outburst floods (GLOFs) have originated in the region, causing approximately 7000 deaths and considerable economic losses. Identifying potentially dangerous glacial lakes (PDGLs) is considered the first step in assessing GLOF risks. In this study, a more thorough inventory of PDGLs was presented that included numerous small-sized glacial lakes (<0.1 km2) that were generally neglected in the Himalayas for decades. Moreover, the PDGL evaluation system was improved in response to several deficiencies, such as the selection of assessment factors, which are sometimes arbitrary without a solid scientific basis. We designed an optimality experiment to select the best combination of assessment factors from 57 factors to identify PDGLs. Based on the experiments on both drained and non-drained glacial lakes in the Sunkoshi Basin, eastern Himalayas, five assessment factors were determined to be the best combination: the mean slope of the parent glacier, the potential for mass movement into the lake, the mean slope of moraine dams, the watershed area, and the lake perimeter, corresponding to the GLOF triggers for ice avalanches, rockfalls and landslides, dam instability, heavy precipitation or other liquid inflows, and lake characteristics, respectively. We then applied the best combination of assessment factors to the 1650 glacial lakes with an area greater than 0.02 km2 in the Himalayas. We identified 207 glacial lakes as very high-hazard and 345 as high-hazard. It is noteworthy that in various GLOF susceptibility evaluation scenarios with different assessment factors, weighting schemes, and classification approaches, similar results for glacial lakes with high outburst potential have been obtained. The results provided here can be used as benchmark data to assess the GLOF risks for local communities.


Asunto(s)
Cubierta de Hielo , Lagos , Inundaciones
3.
Sci Total Environ ; 805: 150334, 2022 Jan 20.
Artículo en Inglés | MEDLINE | ID: mdl-34818791

RESUMEN

Microplastic (MPs) contamination is ubiquitous in most terrestrial and aquatic ecosystems. Recently MPs have been reported at high altitudes which indicates that air masses can transport and deposit MPs in the surface snow of high mountain ecosystems, however, whether MPs typification and abundance can be influenced by direction and origin of air masses still remains an open question. Here we present the first report of MPs above 5000 m a.s.l from surface snow of a glacier in the tropical Andes. We collected surface snow along an elevational gradient, from 5000 to 5400 m a.s.l., in the Antisana Glacier, in the northern Andes cordillera of Ecuador to analyze MPs abundance and polymeric identification with the Fourier Transform Infrared (FTIR) and also to hypothesized the possible MPs sources in this remote area by comparing the oxygen and hydrogen stable isotopic ratio composition of the snow samples and by analyzing the wind direction. We observed an average of 131 ± 24 MPs L-1 in our samples. Fibers corresponded to 70% of all MP shapes; FTIR results showed that MPs composition mainly included polyurethane, polyethylene, polyamide, polyester, and high-density polyethylene in surface snow. There were no statistically significant differences of MPs abundance among sampled elevations, and the isotopic ratio composition did not differ among locations. Our results suggest that MP that accumulated in the glacier may be transported from the east, across the Amazonia, by the prevalent eastward air flow. The absence of industrial cities at least 2000 km further east from Antisana, indicates that the remote Andean glaciers could constitute important depositional zones for long-distance transported contaminants.


Asunto(s)
Microplásticos , Contaminantes Químicos del Agua , Ecosistema , Monitoreo del Ambiente , Cubierta de Hielo , Plásticos , Contaminantes Químicos del Agua/análisis
4.
Sci Total Environ ; 802: 149872, 2022 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-34461480

RESUMEN

In many high altitude river basins, the hydro-climatic regimes and the spatial and temporal distribution of precipitation are little known, complicating efforts to quantify current and future water availability. Scarce, or non-existent, gauged observations at high altitudes coupled with complex weather systems and orographic effects further prevent a realistic and comprehensive assessment of precipitation. Quantifying the contribution from seasonal snow and glacier melt to the river runoff for a high altitude, melt dependent region is especially difficult. Global scale precipitation products, in combination with precipitation-runoff modelling may provide insights to the hydro-climatic regimes for such data scarce regions. In this study two global precipitation products; the high resolution (0.1°â€¯× 0.1°), newly developed ERA5-Land, and a coarser resolution (0.55°â€¯× 0.55°) JRA-55, are used to simulate snow/glacier melts and runoff for the Gilgit Basin, a sub-basin of the Indus. A hydrological precipitation-runoff model, the Distance Distribution Dynamics (DDD), requires minimum input data and was developed for snow dominated catchments. The mean of total annual precipitation from 1995 to 2010 data was estimated at 888 mm and 951 mm by ERA5-Land and JRA-55, respectively. The daily runoff simulation obtained a Kling Gupta efficiency (KGE) of 0.78 and 0.72 with ERA5-Land and JRA-55 based simulations, respectively. The simulated snow cover area (SCA) was validated using MODIS SCA and the results are quite promising on daily, monthly and annual scales. Our result showed an overall contribution to the river flow as about 26% from rainfall, 37-38% from snow melt, 31% from glacier melt and 5% from soil moisture. These melt simulations are in good agreement with the overall hydro-climatic regimes and seasonality of the area. The proxy energy balance approach in the DDD model, used to estimate snow melt and evapotranspiration, showed robust behaviour and potential for being employed in data poor basins.


Asunto(s)
Monitoreo del Ambiente , Nieve , Hidrología , Cubierta de Hielo , Ríos
5.
Sci Total Environ ; 803: 149889, 2022 Jan 10.
Artículo en Inglés | MEDLINE | ID: mdl-34482131

RESUMEN

The Tibetan Plateau (TP) is a global warming hotspot, however, the warming status at high elevation (>5000 m) is poorly understood due to very sparse observations. Here we analyze spatial patterns in TP warming rates based on a novel near-surface air temperature dataset of 1980-2014 recently developed by ingesting high-elevation observations and downscaled reanalysis datasets. We show that the high snow cover persistence at high elevation reduces strengthening of positive feedbacks responsible for elevation dependent warming at low-middle elevations, leading to reversed altitudinal patterns of TP warming above and below 5000 m. An important negative feedback is induced by the presence of snow and glaciers at elevations above 5000 m, due to their "buffering" effects by consuming or reflecting energy that would be used for warming in the absence of snow or ice. A further decrease in snow cover and glacier extent at high elevations may thus amplify the warming on the TP.


Asunto(s)
Monitoreo del Ambiente , Nieve , Cubierta de Hielo , Temperatura , Tibet
6.
Sci Total Environ ; 803: 150002, 2022 Jan 10.
Artículo en Inglés | MEDLINE | ID: mdl-34482143

RESUMEN

Dimethyl sulfide (DMS) produced by marine algae represents the largest natural emission of sulfur to the atmosphere. The oxidation of DMS is a key process affecting new particle formation that contributes to the radiative forcing of the Earth. In this study, atmospheric DMS and its major oxidation products (methanesulfonic acid, MSA; non-sea-salt sulfate, nss-SO42-) and particle size distributions were measured at King Sejong station located in the Antarctic Peninsula during the austral spring-summer period in 2018-2020. The observatory was surrounded by open ocean and first-year and multi-year sea ice. Importantly, oceanic emissions and atmospheric oxidation of DMS showed distinct differences depending on source regions. A high mixing ratio of atmospheric DMS was observed when air masses were influenced by the open ocean and first-year sea ice due to the abundance of DMS producers such as pelagic phaeocystis and ice algae. However, the concentrations of MSA and nss-SO42- were distinctively increased for air masses originating from first-year sea ice as compared to those originating from the open ocean and multi-year sea ice, suggesting additional influences from the source regions of atmospheric oxidants. Heterogeneous chemical processes that actively occur over first-year sea ice tend to accelerate the release of bromine monoxide (BrO), which is the most efficient DMS oxidant in Antarctica. Model-estimates for surface BrO confirmed that high BrO mixing ratios were closely associated with first-year sea ice, thus enhancing DMS oxidation. Consequently, the concentration of newly formed particles originated from first-year sea ice, which was a strong source area for both DMS and BrO was greater than from open ocean (high DMS but low BrO). These results indicate that first-year sea ice plays an important yet overlooked role in DMS-induced new particle formation in polar environments, where warming-induced sea ice changes are pronounced.


Asunto(s)
Cubierta de Hielo , Agua de Mar , Regiones Antárticas , Sulfuros/análisis
7.
Sci Total Environ ; 806(Pt 3): 151289, 2022 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-34717994

RESUMEN

Glacial lake outburst floods (GLOFs) are one of the major natural hazards in certain populated mountainous areas, e.g., the Himalayan region, which may lead to catastrophic consequences including substantial loss of lives. Evaluating the potential socio-economic impact of GLOFs is essential for risk mitigation and enhancing community resilience. Yet in most of the cases, this is confronted with the challenges of limited availability of data and inaccessibility to most of the glacial lakes in the high-altitude areas. This study aims to exploit open data from different sources and high-performance hydrodynamic modelling to develop a new framework for GLOF exposure and impact assessment. In the new framework, different GLOF scenarios are created using a simple dam breach model. A high-performance hydrodynamic model is then adopted to simulate the resulting flood hydrodynamics. Necessary socio-economic information is collected and processed from multiple sources including OpenStreetMap, Google Earth, and global data products to support exposure analysis. Established depth-damage curves are used to assess the GLOF damage extents to different exposed objects and an existing fatality estimating procedure is adopted to assess the potential loss of lives. The evaluation framework is applied to the Tsho Rolpa glacial lake in Nepal. From the results, the worst GLOF scenario as considered can potentially inundate 1647 buildings, impact 5038 people and hit 123 key facilities including schools, hospitals, airports, hydropower plants, etc. It may substantially damage 900 buildings, 10.63 km2 of agricultural land and 50.9 km roads and may potentially lead to 45 deaths even if warning is available.


Asunto(s)
Inundaciones , Lagos , Humanos , Hidrodinámica , Cubierta de Hielo , Nepal
8.
Glob Chang Biol ; 28(1): 8-20, 2022 01.
Artículo en Inglés | MEDLINE | ID: mdl-34658117

RESUMEN

Global warming is causing significant losses of marine ice around the polar regions. In Antarctica, the retreat of tidewater glaciers is opening up novel, low-energy habitats (fjords) that have the potential to provide a negative feedback loop to climate change. These fjords are being colonized by organisms on and within the sediment and act as a sink for particulate matter. So far, blue carbon potential in Antarctic habitats has mainly been estimated using epifaunal megazoobenthos (although some studies have also considered macrozoobenthos). We investigated two further pathways of carbon storage and potential sequestration by measuring the concentration of carbon of infaunal macrozoobenthos and total organic carbon (TOC) deposited in the sediment. We took samples along a temporal gradient since time of last glacier ice cover (1-1000 years) at three fjords along the West Antarctic Peninsula. We tested the hypothesis that seabed carbon standing stock would be mainly driven by time since last glacier covered. However, results showed this to be much more complex. Infauna were highly variable over this temporal gradient and showed similar total mass of carbon standing stock per m2 as literature estimates of Antarctic epifauna. TOC mass in the sediment, however, was an order of magnitude greater than stocks of infaunal and epifaunal carbon and increased with time since last ice cover. Thus, blue carbon stocks and recent gains around Antarctica are likely much higher than previously estimated as is their negative feedback on climate change.


Asunto(s)
Cambio Climático , Cubierta de Hielo , Regiones Antárticas , Carbono , Ecosistema , Estuarios , Retroalimentación
10.
PLoS One ; 16(12): e0261418, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34914776

RESUMEN

The Arctic is experiencing rapid changes in sea-ice seasonality and extent, with significant consequences for primary production. With the importance of accurate monitoring of spring phytoplankton dynamics in a changing Arctic, this study further examines the previously established critical relationship between spring phytoplankton bloom types and timing of the sea-ice retreat for broader temporal and spatial coverages, with a particular focus on the Pacific Arctic for 2003-2019. To this end, time-series of satellite-retrieved phytoplankton biomass were modeled using a parametric Gaussian function, as an effective approach to capture the development and decay of phytoplankton blooms. Our sensitivity analysis demonstrated accurate estimates of timing and presence/absence of peaks in phytoplankton biomass even with some missing values, suggesting the parametric Gaussian function is a powerful tool for capturing the development and decay of phytoplankton blooms. Based on the timing and presence/absence of a peak in phytoplankton biomass and following the classification developed by the previous exploratory work, spring bloom types are classified into three groups (under-ice blooms, probable under-ice blooms, and marginal ice zone blooms). Our results showed that the proportion of under-ice blooms was higher in the Chukchi Sea than in the Bering Sea. The probable under-ice blooms registered as the dominant bloom types in a wide area of the Pacific Arctic, whereas the marginal ice zone bloom was a relatively minor bloom type across the Pacific Arctic. Associated with a shift of sea-ice retreat timing toward earlier dates, we confirmed previous findings from the Chukchi Sea of recent shifts in phytoplankton bloom types from under-ice blooms to marginal ice zone blooms and demonstrated that this pattern holds for the broader Pacific Arctic sector for the time period 2003-2019. Overall, the present study provided additional evidence of the changing sea-ice retreat timing that can drive variations in phytoplankton bloom dynamics, which contributes to addressing the detection and consistent monitoring of the biophysical responses to the changing environments in the Pacific Arctic.


Asunto(s)
Eutrofización , Cubierta de Hielo , Fitoplancton/crecimiento & desarrollo , Regiones Árticas , Biomasa , Clorofila A/análisis , Clima , Ecosistema , Océano Pacífico , Imágenes Satelitales , Estaciones del Año , Temperatura
11.
Sensors (Basel) ; 21(24)2021 Dec 20.
Artículo en Inglés | MEDLINE | ID: mdl-34960600

RESUMEN

Continuous monitoring of ice cover belongs to the key tasks of modern climate research, providing up-to-date information on climate change in cold regions. While a strong advance in ice monitoring worldwide has been provided by the recent development of remote sensing methods, quantification of seasonal ice cover is impossible without on-site autonomous measurements of the mass and heat budget. In the present study, we propose an autonomous monitoring system for continuous in situ measuring of vertical temperature distribution in the near-ice air, the ice strata and the under-ice water layer for several months with simultaneous records of solar radiation incoming at the lake surface and passing through the snow and ice covers as well as snow and ice thicknesses. The use of modern miniature analog and digital sensors made it possible to make a compact, energy efficient measurement system with high precision and spatial resolution and characterized by easy deployment and transportation. In particular, the high resolution of the ice thickness probe of 0.05 mm allows to resolve the fine-scale processes occurring in low-flow environments, such as freshwater lakes. Several systems were tested in numerous studies in Lake Baikal and demonstrated a high reliability in deriving the ice heat balance components during ice-covered periods.


Asunto(s)
Cubierta de Hielo , Lagos , Cambio Climático , Reproducibilidad de los Resultados , Nieve
12.
Int J Syst Evol Microbiol ; 71(12)2021 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-34919039

RESUMEN

Two Gram-stain-positive, aerobic, rod-shaped, pink and light pink colony-forming bacteria, designated as Hz2T and MDT2-14T, respectively, were isolated from glacier cryoconite samples. Comparisons based on 16S rRNA gene sequences showed that strains Hz2T and MDT2-14T take Arthrobacter bussei KR32T and Arthrobacter zhaoguopingii J391T as their closest neighbours, respectively. The average nucleotide identity values between the two novel strains and their closest relatives were 83.56 and 93.06 %, respectively. The two strains contain MK-9(H2) as their predominant menaquinone. The polar lipids of both strains were phosphatidylglycerol, diphosphatidylglycerol, phosphatidylinositol and an unidentified glycolipid. The major fatty acids of strain Hz2T were anteiso-C15 : 0, summed feature 3 (comprising C16 : 1 ω7c and/or C16 : 1 ω6c) and iso-C15 : 0, while the major fatty acids of strain MDT2-14T were anteiso-C15 : 0 and anteiso-C17 : 0. Based on these data, we propose two novel species, Arthrobacter cheniae sp. nov. (Hz2T = CGMCC 1.9262T=NBRC 113086T) and Arthrobacter frigidicola sp. nov. (MDT2-14T=CGMCC 1.9882T=NBRC 113089T).


Asunto(s)
Arthrobacter , Arthrobacter/genética , Técnicas de Tipificación Bacteriana , Composición de Base , ADN Bacteriano/genética , Ácidos Grasos/química , Cubierta de Hielo , Filogenia , ARN Ribosómico 16S/genética , Análisis de Secuencia de ADN
13.
Environ Monit Assess ; 193(11): 761, 2021 Nov 01.
Artículo en Inglés | MEDLINE | ID: mdl-34719750

RESUMEN

The Upper Indus Basin has a large concentration of glaciers and mainly fed by snow and glacier melt. These melt runoffs are the primary driver of discharge and significantly contribute to Indus flows. Therefore, the present study was undertaken in the Upper Indus Basin (UIB) up to the Besham Quila site. This study focuses on quantifying runoff's contribution from different sources, including snow and glacier melt, and evaluates model performance in the glacierized Himalayan basin. The model was calibrated (1981-2000) and validated (2001-2007) daily and monthly using 27 years of measured discharge data at the Besham Quila station. A statistical indicator shows a "good" relationship between simulated and observed discharge on a daily and "very good" on a monthly timestamp. In this study, the annual contribution from snow/ice melt in the basin was quantified and found to be 51% of the total runoff. Apart from this, around 30% of water comes from direct runoff generated through liquid precipitation and 3.8% from groundwater. The remaining (~15%) is contributed by interflows sourced from the rainfall and snow/ice melt. The basin receives 61% contribution from snow and glacier melt during monsoon (July-Sept) and 38% during summer (April-June) seasons, while negligible in other seasons. A decreasing trend is observed in modelled total runoff and melt runoff of about 1.11 × 109 m3 a-1 and 0.73 × 109 m3 a-1, respectively.


Asunto(s)
Cubierta de Hielo , Nieve , Cambio Climático , Monitoreo del Ambiente , Ríos
14.
Environ Sci Process Impacts ; 23(11): 1759-1770, 2021 Nov 17.
Artículo en Inglés | MEDLINE | ID: mdl-34610635

RESUMEN

Plastic debris accumulates in the Arctic by way of oceanic and atmospheric circulation. High concentrations of microplastics (1 µm to 5 mm) have been measured, and nanoplastics (<1 µm) are expected to be abundant as well. However, little is known about the mobility of micro- and nanoplastics at the seawater/ice interface. This study investigates the fate of micro- and nanoplastics during sea-ice formation. A novel experimental approach simulates the growth of sea ice by progressively freezing a saline solution. After different durations of freezing, the concentrations of NaCl, natural organic matter, microplastics, and nanoplastics were measured in the ice and liquid. Micro- and nanoplastic distribution coefficients between saltwater and ice were determined, reflecting their behavior during congelation sea-ice growth. The results show that microplastics are retained in ice while nanoplastics are expulsed from it. Furthermore, natural organic matter plays a crucial role in stabilizing nanoplastics at this interface. These results raise new questions concerning the impact of micro- and nanoplastics in fragile polar environments and the analytical strategy to detect them.


Asunto(s)
Microplásticos , Plásticos , Congelación , Cubierta de Hielo , Agua de Mar
15.
Environ Monit Assess ; 193(11): 726, 2021 Oct 16.
Artículo en Inglés | MEDLINE | ID: mdl-34655335

RESUMEN

The present study provides the first multi-year (2015-2020) random observation of black carbon (BC) aerosols from pristine localities along the Gangotri Glacier Valley in the north-western Indian Himalaya. Due to the harsh climatic conditions and inaccessible terrain, hardly any BC observation is available from glaciated Himalaya. To investigate the background concentration of BC in the high Himalaya, random measurements are conducted at five locations at variable microclimates with different anthropogenic influences along a 24-km-long Gangotri Glacier Valley trek, viz. Gangotri (~ 3200 m amsl), Chirbasa (~ 3600 m amsl), Bhojbasa (~ 3800 m amsl), Gaumukh (~ 4000 m amsl), and Tapovan (~ 4400 m amsl). A relatively high concentration of BC (up to 2.23 ± 0.57 µg m-3) was recorded at Gangotri which is a famous Indian pilgrimage centre which remains highly crowded during the peak tourist season, i.e. May-June and Oct-Nov every year. Surprisingly, we also recorded high BC (up to 1.27 ± 0.57 µg m-3) at Tapovan, which is a high altitude meadow surrounded by high ice-snow peaks, viz. Bhagirathi Peak (6856 m amsl), Shivling (6543 m amsl), and Meru Parvat (6660 m amsl). The HYSPLIT cluster trajectory and CALIPSO data images suggest that besides local anthropogenic activities, polluted air mass-produced due to burning of forest and agriculture biomass and fossil fuels, etc. transported from Indo Gangetic Basin might be playing a potential role in ambient BC concentration in the study area. The present preliminary investigations of BC in the Gangotri Glacier Valley open new vision and possibilities for further extensive ground-based observation of aerosol air pollutants in Himalayan glacier valley systems.


Asunto(s)
Contaminantes Atmosféricos , Contaminantes Ambientales , Aerosoles/análisis , Contaminantes Atmosféricos/análisis , Carbono/análisis , Ecosistema , Monitoreo del Ambiente , Cubierta de Hielo , Proyectos Piloto
16.
Environ Monit Assess ; 193(11): 724, 2021 Oct 14.
Artículo en Inglés | MEDLINE | ID: mdl-34648070

RESUMEN

Global environmental changes not only contribute to the modification of global pollution transport pathways but can also alter contaminant fate within the Arctic. Recent reports underline the importance of secondary sources of pollution, e.g. melting glaciers, thawing permafrost or increased riverine run-off. This article reviews reports on the European Arctic-we concentrate on the Svalbard region-and environmental contamination by inorganic pollutants (heavy metals and artificial radionuclides), including their transport pathways, their fate in the Arctic environment and the concentrations of individual elements in the ecosystem. This review presents in detail the secondary contaminant sources and tries to identify knowledge gaps, as well as indicate needs for further research. Concentrations of heavy metals and radionuclides in Svalbard have been studied, in various environmental elements since the beginning of the twentieth century. In the last 5 years, the highest concentrations of Cd (13 mg kg-1) and As (28 mg kg-1) were recorded for organic-rich soils, while levels of Pb (99 mg kg-1), Hg (1 mg kg-1), Zn (496 mg kg-1) and Cu (688 mg kg-1) were recorded for marine sediments. Increased heavy metal concentrations were also recorded in some flora and fauna species. For radionuclides in the last 5 years, the highest concentrations of 137Cs (4500 Bq kg-1), 238Pu (2 Bq kg-1) and 239 + 240Pu (43 Bq kg-1) were recorded for cryoconites, and the highest concentration of 241Am (570 Bq kg-1) was recorded in surface sediments. However, no contamination of flora and fauna with radionuclides was observed.


Asunto(s)
Ecosistema , Metales Pesados , Regiones Árticas , Monitoreo del Ambiente , Cubierta de Hielo , Metales Pesados/análisis , Svalbard
17.
Am Nat ; 198(5): 590-609, 2021 11.
Artículo en Inglés | MEDLINE | ID: mdl-34648394

RESUMEN

AbstractAnimals, fungi, and algae with complex multicellular bodies all evolved independently from unicellular ancestors. The early history of these major eukaryotic multicellular clades, if not their origins, co-occur with an extreme phase of global glaciations known as the Snowball Earth. Here, I propose that the long-term loss of low-viscosity environments due to several rounds global glaciation drove the multiple origins of complex multicellularity in eukaryotes and the subsequent radiation of complex multicellular groups into previously unoccupied niches. In this scenario, life adapts to Snowball Earth oceans by evolving large size and faster speeds through multicellularity, which acts to compensate for high-viscosity seawater and achieve fluid flow at sufficient levels to satisfy metabolic needs. Warm, low-viscosity seawater returned with the melting of the Snowball glaciers, and with it, by virtue of large and fast multicellular bodies, new ways of life were unveiled.


Asunto(s)
Cubierta de Hielo , Agua de Mar , Aclimatación , Hongos , Viscosidad
18.
PLoS One ; 16(9): e0253768, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34499651

RESUMEN

The Labyrinth in the McMurdo Dry Valleys of Antarctica is characterized by large bedrock channels emerging from beneath the margin of Wright Upper Glacier. To study the morphodynamics of large subglacial channels cut into bedrock, we develop herein a numerical model based on the classical theory of subglacial channels and recent results on bedrock abrasion by saltating bed load. Model results show that bedrock abrasion in subglacial channels with pressurized flow reaches a maximum at an intermediate distance up-ice from the glacier snout for a wide range of sediment grain sizes and sediment loads. Close to the snout, the velocity is too low and the sediment particles cannot be mobilized. Far from the snout, the flow accelerates and sediment is transported in suspension, thus limiting particle impacts at the channel bottom and reducing abrasion. This non-monotonic relationship between subglacial flow and bedrock abrasion produces concave up bottom profiles in subglacial channels and potential cross-section constrictions after channel confluences. Both landforms are present in the bedrock channels of the Labyrinth. We therefore conclude that these geomorphic features are a possible signature of bedrock abrasion, rather than glacial scour, and reflect the complex interplay between transport rate, sediment load, and transport capacity in subglacial channels.


Asunto(s)
Sedimentos Geológicos/análisis , Cubierta de Hielo , Modelos Teóricos , Erosión del Suelo
19.
Glob Chang Biol ; 27(23): 6181-6191, 2021 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-34582605

RESUMEN

Polar seafloor ecosystems are changing rapidly and dramatically, challenging previously held paradigms of extreme dynamical stability. Warming-related declines in polar sea ice are expected to alter fluxes of phytoplankton and under-ice algae to the seafloor. Yet, how changes in food flux cascade through to seafloor communities and functions remains unclear. We leveraged natural spatial and temporal gradients in summertime sea ice extent to better understand the trajectories and implications of climate-related change in McMurdo Sound, Antarctica. McMurdo Sound was expected to be one of the last coastal marine environments on Earth to be affected by planetary warming, but the situation may be changing. Comparing satellite observations of selected coastal sites in McMurdo Sound between 2010-2017 and 2002-2009 revealed more ice-free days per year, and shorter distances to open water during the warmest months each year, in the more recent period. Interdecadal Pacific Oscillation (IPO), Oceanic Niño Index (ONI) and Antarctic Oscillation (AAO) climate indices peaked concurrently between 2014 and 2017 when sea ice breakouts in McMurdo Sound were most spatially and temporally extensive. Increases in sediment chlorophyll a and phaeophytin content (indicating increased deposition of detrital algal food material) were recorded during 2014-2017 at three coastal study sites in McMurdo Sound following the major sea ice breakouts. Soft-sediment seafloor ecosystem metabolism (measured in benthic incubation chambers as dissolved oxygen and inorganic nutrient fluxes) was correlated with sediment algal pigment concentration. Epifaunal invertebrate density, particularly opportunistic sessile suspension feeders, and infaunal community composition also shifted with increased food supply. The ecological characteristics and functions measured at the food-poor sites shifted towards those observed at richer sites at a surprisingly fast pace. These results indicate the sensitivity of the benthos and shed light on Antarctic marine trophic cascades and trajectories of response of iconic high-latitude seafloor habitats to a warming climate.


Asunto(s)
Ecosistema , Cubierta de Hielo , Regiones Antárticas , Clorofila A , Clima
20.
Ambio ; 50(11): 2104-2127, 2021 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-34586591

RESUMEN

A recent multidisciplinary compilation of studies on changes in the Siberian environment details how climate is changing faster than most places on Earth with exceptional warming in the north and increased aridity in the south. Impacts of these changes are rapid permafrost thaw and melt of glaciers, increased flooding, extreme weather events leading to sudden changes in biodiversity, increased forest fires, more insect pest outbreaks, and increased emissions of CO2 and methane. These trends interact with sociological changes leading to land-use change, globalisation of diets, impaired health of Arctic Peoples, and challenges for transport. Local mitigation and adaptation measures are likely to be limited by a range of public perceptions of climate change that vary according to personal background. However, Siberia has the possibility through land surface feedbacks to amplify or suppress climate change impacts at potentially global levels. Based on the diverse studies presented in this Ambio Special Issue, we suggest ways forward for more sustainable environmental research and management.


Asunto(s)
Ecosistema , Hielos Perennes , Regiones Árticas , Cambio Climático , Cubierta de Hielo , Siberia
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