scholarly journals Numerical modelling of permafrost spring discharge and open-system pingo formation induced by basal permafrost aggradation

2020 ◽  
Vol 14 (12) ◽  
pp. 4627-4651
Author(s):  
Mikkel Toft Hornum ◽  
Andrew Jonathan Hodson ◽  
Søren Jessen ◽  
Victor Bense ◽  
Kim Senger
Keyword(s):  
Conceptual Model ◽  
Open System ◽  
Pressure Effects ◽  
The Arctic ◽  
Spring Discharge ◽  
Driving Mechanism ◽  
Hydraulic Pressure ◽  
Transport Modelling ◽  
Groundwater System ◽  
Millennial Scale

Abstract. In the high Arctic valley of Adventdalen, Svalbard, sub-permafrost groundwater feeds several pingo springs distributed along the valley axis. The driving mechanism for groundwater discharge and associated pingo formation is enigmatic because wet-based glaciers are not present in the adjacent highlands and the presence of continuous permafrost seems to preclude recharge of the sub-permafrost groundwater system by either a subglacial source or a precipitation surplus. Since the pingo springs enable methane that has accumulated underneath the permafrost to escape directly to the atmosphere, our limited understanding of the groundwater system brings significant uncertainty to predictions of how methane emissions will respond to changing climate. We address this problem with a new conceptual model for open-system pingo formation wherein pingo growth is sustained by sub-permafrost pressure effects, as related to the expansion of water upon freezing, during millennial-scale basal permafrost aggradation. We test the viability of this mechanism for generating groundwater flow with decoupled heat (one-dimensional transient) and groundwater (three-dimensional steady state) transport modelling experiments. Our results suggest that the conceptual model represents a feasible mechanism for the formation of open-system pingos in lower Adventdalen and elsewhere. We also explore the potential for additional pressurisation and find that methane production and methane clathrate formation and dissolution deserve particular attention on account of their likely effects upon the hydraulic pressure. Our model simulations also suggest that the generally low-permeability hydrogeological units cause groundwater residence times to exceed the duration of the Holocene. The likelihood of such pre-Holocene groundwater ages is supported by the geochemistry of the pingo springs which demonstrates an unexpected seaward freshening of groundwater potentially caused by a palaeo-subglacial meltwater “wedge” from the Weichselian. Whereas permafrost thickness (and age) progressively increases inland, accordingly, the sub-permafrost meltwater wedge thins, and less unfrozen freshwater is available for mixing. Our observations imply that millennial-scale permafrost aggradation deserves more attention as a possible driver of sustained flow of sub-permafrost groundwater and methane to the surface because, although the hydrological system in Adventdalen at first appears unusual, it is likely that similar systems have developed in other uplifted valleys throughout the Arctic.

scholarly journals Numerical modelling of permafrost spring discharge and open-system pingo formation induced by basal permafrost aggradation

2020 ◽  
Author(s):  
Mikkel T. Hornum ◽  
Andrew J. Hodson ◽  
Søren Jessen ◽  
Victor Bense ◽  
Kim Senger
Keyword(s):  
Conceptual Model ◽  
Open System ◽  
High Arctic ◽  
Pressure Effects ◽  
Spring Discharge ◽  
Driving Mechanism ◽  
Transport Modelling ◽  
Groundwater System ◽  
Clathrate Formation ◽  
Methane Clathrate

Abstract. In the high Arctic valley of Adventdalen, Svalbard, sub-permafrost groundwater feeds several pingo springs distributed along the valley axis. The driving mechanism for groundwater discharge and associated pingo formation is enigmatic because wet-based glaciers in the adjacent highlands and the presence of continuous permafrost seem to preclude recharge of the sub-permafrost groundwater system by either a sub-glacial source or a precipitation surplus. Since the pingo springs enable methane that has accumulated underneath the permafrost to escape directly to the atmosphere, our limited understanding of the groundwater system brings significant uncertainty to the understanding of how methane emissions will respond to changing climate. We address this problem with a new conceptual model for open-system pingo formation wherein pingo growth is sustained by sub-permafrost pressure effects during millennial scale basal permafrost aggradation. We test the viability of this mechanism for generating groundwater flow with decoupled heat (1D-transient) and groundwater (2D-steady-state) transport modelling experiments. Our results show that the pingos in lower Adventdalen easily conform to this conceptual model. Simulations suggest that the generally low-permeability hydrogeological units cause groundwater residence times that exceed the duration of the Holocene. The likelihood of such pre-Holocene groundwater ages is also supported by the hydrogeochemistry of the pingo springs, which demonstrate a sea-wards freshening of groundwater, potentially supplied by paleo-subglacial melting during the Weichselian. Such waters form a sub-permafrost fresh water wedge that progressively thins inland, where the duration of permafrost aggradation is longest. The mixing ratio of the underlying marine waters therefore increases in this direction because less unfrozen freshwater is available for mixing. Although this unusual hydraulic system is most likely governed by permafrost aggradation, the potential for additional pressurization is also explored. We conclude that methane production and methane clathrate formation may also affect hydraulic the pressure in sub-permafrost aquifers, but additional research is needed to fully establish their influence.

scholarly journals Distribution and Driving Mechanism of N2O in Sea Ice and Its Underlying Seawater during Arctic Melt Season

Water ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 145
Author(s):  
Jian Liu ◽  
Liyang Zhan ◽  
Qingkai Wang ◽  
Man Wu ◽  
Wangwang Ye ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Ice Core ◽  
The Arctic ◽  
First Year ◽  
Driving Mechanism ◽  
Biogeochemical Processes ◽  
Ice Melting ◽  
Detailed Mechanism ◽  
The Arctic Ocean

Nitrous oxide (N2O) is the third most important greenhouse gas in the atmosphere, and the ocean is an important source of N2O. As the Arctic Ocean is strongly affected by global warming, rapid ice melting can have a significant impact on the N2O pattern in the Arctic environment. To better understand this impact, N2O concentration in ice core and underlying seawater (USW) was measured during the seventh Chinese National Arctic Research Expedition (CHINARE2016). The results showed that the average N2O concentration in first-year ice (FYI) was 4.5 ± 1.0 nmol kg−1, and that in multi-year ice (MYI) was 4.8 ± 1.9 nmol kg−1. Under the influence of exchange among atmosphere-sea ice-seawater systems, brine dynamics and possible N2O generation processes at the bottom of sea ice, the FYI showed higher N2O concentrations at the bottom and surface, while lower N2O concentrations were seen inside sea ice. Due to the melting of sea ice and biogeochemical processes, USW presented as the sink of N2O, and the saturation varied from 47.2% to 102.2%. However, the observed N2O concentrations in USW were higher than that of T-N2OUSW due to the sea–air exchange, diffusion process, possible N2O generation mechanism, and the influence of precipitation, and a more detailed mechanism is needed to understand this process in the Arctic Ocean.

scholarly journals Enhanced Characterization of the Krania–Elassona Structure and Functioning Allogenic Karst Aquifer in Central Greece

Geosciences ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 15 ◽  
Author(s):  
Antonios Manakos ◽  
Maria Ntona ◽  
Nerantzis Kazakis ◽  
Konstantinos Chalikakis
Keyword(s):  
Conceptual Model ◽  
Moving Average ◽  
Karst Aquifer ◽  
Groundwater Vulnerability ◽  
Spring Water ◽  
Geological Mapping ◽  
Spring Discharge ◽  
Water Type ◽  
Central Greece

The present study highlights the importance of geological, hydrogeological, and hydrogeochemical characterization of a karst aquifer in building a conceptual model of the system. The karst system of Krania–Elassona in central Greece was chosen for this application. Hydrogeological research included geological mapping and hydrogeological analysis. Additionally, hydrochemical analysis of water samples was performed in boreholes, rivers, and the system’s main spring. The Krania–Elassona aquifer consists of three horizons of marbles and is characterized by mature karstification. The karst aquifer is characterized by allogenic recharge mainly from the River Deskatis that accounts for up to 92% of the total flow. Groundwater and spring water are generally characterized as good quality and are suitable for irrigation and domestic use. The water type of the spring water is classified as Mg-HCO3. The application of a SARIMA (Seasonal Autoregressive Integrated Moving Average Model) model verified the conceptual model and successfully simulated spring discharge for a two-year period. The results of this study highlight the importance of basic hydrogeological research and the initial conceptualization of karst systems in reliably assessing groundwater vulnerability and modeling.

scholarly journals Enhanced 20th-century heat transfer to the Arctic simulated in the context of climate variations over the last millennium

2014 ◽  
Vol 10 (6) ◽  
pp. 2201-2213 ◽  
Author(s):  
J. H. Jungclaus ◽  
K. Lohmann ◽  
D. Zanchettin
Keyword(s):  
Heat Transfer ◽  
20Th Century ◽  
Ocean Circulation ◽  
Internal Variability ◽  
Atlantic Water ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Driving Mechanism ◽  
Last Millennium ◽  
Fram Strait

Abstract. Oceanic heat transport variations, carried by the northward-flowing Atlantic Water, strongly influence Arctic sea-ice distribution, ocean–atmosphere exchanges, and pan-Arctic temperatures. Palaeoceanographic reconstructions from marine sediments near Fram Strait have documented a dramatic increase in Atlantic Water temperatures over the 20th century, unprecedented in the last millennium. Here we present results from Earth system model simulations that reproduce and explain the reconstructed exceptional Atlantic Water warming in Fram Strait in the 20th century in the context of natural variability during the last millennium. The associated increase in ocean heat transfer to the Arctic can be traced back to changes in the ocean circulation in the subpolar North Atlantic. An interplay between a weakening overturning circulation and a strengthening subpolar gyre as a consequence of 20th-century global warming is identified as the driving mechanism for the pronounced warming along the Atlantic Water path toward the Arctic. Simulations covering the late Holocene provide a reference frame that allows us to conclude that the changes during the last century are unprecedented in the last 1150 years and that they cannot be explained by internal variability or natural forcing alone.

scholarly journals Micro-hydromechanical deep drawing of metal cups with hydraulic pressure effects

2018 ◽  
Vol 13 (1) ◽  
pp. 66-73 ◽  
Author(s):  
Liang Luo ◽  
Zhengyi Jiang ◽  
Dongbin Wei ◽  
Xiaogang Wang ◽  
Cunlong Zhou ◽  
...  
Keyword(s):  
Deep Drawing ◽  
Pressure Effects ◽  
Hydraulic Pressure ◽  
Hydromechanical Deep Drawing

scholarly journals Millennial-to-centennial patterns and trends in the hydroclimate of North America over the past 2000 years

2017 ◽  
Author(s):  
Bryan N. Shuman ◽  
Cody Routson ◽  
Nicholas McKay ◽  
Sherilyn Fritz ◽  
Darrell Kaufman ◽  
...  
Keyword(s):  
Pacific Northwest ◽  
Ice Age ◽  
The Arctic ◽  
Medieval Period ◽  
The Past ◽  
Past 2000 Years ◽  
Annual Range ◽  
The Common ◽  
Common Era ◽  
Millennial Scale

Abstract. A synthesis of 93 hydrologic records from across North and Central America, and adjacent tropical and Arctic islands, reveals centennial to millennial trends in the regional hydroclimates of the Common Era (CE; past 2000 years). The hydrological records derive from materials stored in lakes, bogs, caves, and ice from extant glaciers, which have the continuity through time to preserve low-frequency (> 100 year) climate signals that may not be well represented by other shorter-lived archives, such as tree-ring chronologies. The most common pattern, represented in 46 (49 %) of the records, indicates that the centuries before 1000 CE were drier than the centuries since that time. Principal components analysis indicates that millennial-scale trends represent the dominant pattern of variance in the southwest and northeast U.S., the mid-continent, Pacific Northwest, the Arctic, and the tropics, although not all records within a region show the same direction of change. The Pacific Northwest, Greenland, and the southernmost tier of the tropical sites tended to dry toward present, as many other areas became wetter than before. Twenty-two records (24 %) indicate that the Medieval period (800–1300 CE) was drier than the Little Ice Age (1400–1900 CE), but in many cases the difference was part of the longer millennial-scale trend, and, in 25 records (27 %), the Medieval period represented a pluvial (wet) phase. Where quantitative records permitted a comparison, we found that centennial-scale fluctuations over the Common Era represented changes of 3–7 % of the modern inter-annual range of variability in precipitation, but the accumulation of these long-term trends over the entirety of the Holocene caused recent centuries to be significantly wetter, on average, than most of the past 11 000 years.

scholarly journals CONCEPTUAL MODEL OF FUNCTIONAL ZONING OF TEMPORARY RESIDENCE IN THE ARCTIC REGIONS OF RUSSIA

2019 ◽  
Vol 21 (4) ◽  
pp. 76-93
Author(s):  
A. E. Tokarev
Keyword(s):  
Urban Planning ◽  
Conceptual Model ◽  
National Park ◽  
City Planning ◽  
The Arctic ◽  
Far North ◽  
Arctic Regions ◽  
Functional Zoning ◽  
Artificial Environment ◽  
Regions Of Russia

Purpose: The aim of this work is to study the environmental issues of northern urban planning and create a conceptual model of the functional zoning of the temporary residence module for the Far North. The purpose includes summary of the problems and threats of protected natural areas, namely the Arctic National Park of Russia; a study of the main historical town-planning of the ideal cities, clarification of aspects of the modern city planning in extreme conditions ; the analysis of the conceptual project “Cities of the Future”, in which the environmental problem is the main requirement for the artificial environment for human life; a description of urban planning principles and space-planning decisions of existing camps in the north of Russia and reveal the significant shortcomings of construction in these conditions ; formulation and systematization of specific requirements for the modern architecture of temporary Arctic settlements; propose a conceptual model of functional zoning of a temporary residence module in the Far North regions.Research findings: A new composition of the Arctic module for temporary residence of the 21st century is considered. A list and zoning scheme of the main and auxiliary premises, united by functional zones is discussed. The requirements for residential, public and technical spaces of the complex are defined and formulated.Practical implications: The proposed temporary residence modules can be used for Arctic regions of Russia. The functional zoning will allow to create a spatial environment of autonomous bioclimatic temporary residence module for the Russian Arctic National Park.

A system dynamic approach for simulation of a knowledge transfer model of heterogeneous senders in mega project innovation

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Huimin Liu ◽  
Yanru Yu ◽  
Yuxing Sun ◽  
Xue Yan
Keyword(s):  
Knowledge Transfer ◽  
Conceptual Model ◽  
Knowledge Creation ◽  
Academic Research ◽  
Transfer Model ◽  
Driving Mechanism ◽  
Qualitative Model ◽  
Knowledge Stock ◽  
Content Type ◽  
Factors Affecting

PurposeThe owners of mega projects typically assemble multiple academic research units and enterprises to form an innovation alliance, which carries out knowledge transfer and knowledge creation targeting technical challenges in the process of engineering construction. Due to high technical and management complexity of mega projects, factors affecting knowledge transfer among innovation subjects are complex and diverse. This study proposes a mixed system dynamics (SD) method to build and simulate the process of knowledge transfer in mega projects innovation and analyzes the driving mechanism that enhances knowledge stock of enterprises and engineering innovation results.Design/methodology/approachFirst, this paper proposes a conceptual model for knowledge transfer in mega projects by adopting event analysis of the data gained from investigations and interviews. Then, a qualitative model of knowledge transfer that considers mutual influences of the owner, academic research unit and enterprises is developed. Based on that, mathematical relationship among variables of the qualitative model is determined and a quantitative model of knowledge transfer that considers heterogeneity of knowledge sender is built. Finally, simulation is achieved using Vensim software.FindingsThe factors affecting knowledge stock of enterprises are analyzed from three aspects: (1) the individual motives and capability of academic research units and enterprises; (2) the gap between academic research units and enterprises; (3) the heterogeneity of academic research units. The results show that the willingness and capability of knowledge reception by enterprises, specific knowledge transfer context such as relational distance and organization distance between academic research units and enterprises and academic research units with high knowledge stock have key influences on the knowledge stock of enterprises.Research limitations/implicationsFactors affecting knowledge transfer within the alliance of innovation in mega projects and their correlations are highly complicated and difficult to determine. Despite massive investigations and interviews on many long-span bridges in China in this study, it is barely possible to directly obtain accurate data for all variables in the model. Limitations of historical data result in limitations on applications of the proposed model.Practical implicationsBy building the mega projects knowledge transfer model and conducting simulation analysis, this paper has generated practical values for the owners of mega projects on fostering, organizing, coordinating and managing of innovations. Especially, this study provides specific strategies and suggestions on selection of innovation subjects, motivation and guaranteed efficiency of knowledge transfer and knowledge creation of academic research units and enterprises.Originality/valueThis study proposes a conceptual model for factors affecting knowledge transfer that applies to innovations in mega project context, which fills the gap in the research of knowledge management in mega project innovations. Additionally, combining with the method of SD, the unique role of owner in knowledge transfer of mega projects and the differences among various knowledge senders and their influences on knowledge stocks of enterprises are thoroughly considered, and the research method of modeling and simulation of knowledge transfer mechanism is supplemented and extended.

Weihe Basin Drilling Project (WBDP): Cenozoic tectonic-monsoon interactions

2020 ◽  
Author(s):  
Zhisheng An ◽  
Peter Molnar ◽  
Peizhen Zhang ◽  
Hendrik Vogel ◽  
Mark Level ◽  
...  
Keyword(s):  
Climate Variability ◽  
Ice Cores ◽  
The Arctic ◽  
Second Phase ◽  
The Tibetan Plateau ◽  
Sedimentary Record ◽  
Weihe Basin ◽  
Drilling Project ◽  
Millennial Scale

<p>Earth’s climate underwent dramatic cooling throughout much of the Cenozoic, which has been linked to continental drift, mountain building, and the formation and expansion of ice-sheets in Antarctica and the Arctic. In particular, the India-Asia collision and uplift of the Tibetan Plateau (TP) have been posited as critical events responsible for increasing the rates of physical and chemical weathering on land, thereby decreasing the CO2 concentration of the atmosphere. The uplift of the TP ultimately led to the onset of the complexly coupled monsoon-arid environmental system in East Asia. Global-scale studies of Cenozoic deep-sea sediments and Quaternary ice cores indicate that, superimposed to the long-term cooling trend, climate variability at orbital-to-centennial time-scales is primarily induced by changing solar insolation and irradiance, and strongly modulated by complex internal land-air-ocean interactions. From the continental perspective, however, both the dynamics and impacts of long-term climate evolution and short-term climate variability remain poorly constrained due to the paucity of continuous terrestrial sequences spanning the entire Cenozoic.<br>The Weihe Basin is located in the monsoon-sensitive region to the north of the Qinling Mountains, a landform that constitutes the geographic and climatic boundary between northern and southern China. In the depocentre of this basin, a predominantly lacustrine sedimentary sequence with a thickness of >7 km, provides an unprecedented opportunity for: (1) reconstructing tectonic-to-millennial-scale climate changes from the Eocene to the present; (2) elucidating basin-mountain coupling processes; (3) assessing the effects of Cenozoic tectonic-climate interactions on the onset and evolution of the Asian paleomonsoon; and (4) investigating climatic/environmental impacts on the evolution of microbial communities. Importantly also, (5) sedimentary filling of the Weihe Basin can potentially yield unique high-resolution records of continental climate variability during high atmospheric CO2 periods of the Eocene, mid-Miocene, and Late Pliocene, and thus serve an analog for Earth’s near future climate.<br>The Weihe Basin Drilling Project (WBDP) proposes a two-phase drilling strategy to recover a complete as possible Cenozoic terrestrial sedimentary record from the eastern Weihe Basin depocenter. In the first phase (applied for here) we aim at producing a 3-km-long pilot sedimentary record (WBDP-1) to test the best suitable analytical approach and to reconstruct orbital-to-millennial-scale climate variability since the Late Miocene. In the second phase our aim is to produce a 7.5-km-long sedimentary record (WBDP-2) spanning the entire Cenozoic sedimentary infill of the Weihe Basin. The regional geological framework is well characterized through numerous exploration boreholes and detailed multichannel seismic reflection surveys. Scientific drilling operations will be accompanied by downhole logging, as well as on- and off-site analyses of the retrieved cores. The WBDP-1 borehole is expected to yield a world-class paleoclimate record for the last ~10 Ma and lead to fundamental advances in our understanding of multi-timescale climate variability and tectonic-climate monsoon linkages. The project will also enhance public awareness of human adaptation to Earth’s changing environment.</p>

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