Pipeline Geohazards Unique to Northern Climates

2006 ◽  
Author(s):  
Rupert G. Tart
Keyword(s):  
Active Layer ◽  
Heat Removal ◽  
Heat Pipes ◽  
Large Earthquake ◽  
Frost Heave ◽  
Near Surface ◽  
Slope Movements ◽  
Discontinuous Permafrost ◽  
Thaw Settlement ◽  
The Impact

Pipelines in northern climates can be impacted by geohazards that are unique to cold regions. Some of these include frost heave, thaw settlement, solifluction, icings, glaciers, ice-rich slopes, and others. This paper will discuss most of these geohazards as they have been monitored, mitigated, and managed along the Trans Alaska Pipeline (TAPS) and other pipelines in Alaska and Russia. Early analyses of frost heave and thaw settlement of piles concluded that frost heave and thaw settlement would be controlled by installing passive heat removal devices (heat pipes). In permafrost areas heat pipes have generally worked well. In unfrozen terrain or discontinuous permafrost the heat pipes have not been able to maintain stability. Examples of each of these situations will be discussed. Steep rolling terrain makes up a significant part of the TAPS route. Some of the slopes are in permafrost and others are in thawed ground. For the past 15 years, surveillance and monitoring of some of the slopes along the pipeline route has documented the response of slopes in frozen ground. Warmer (that is near 0 degrees C) ice-rich slopes can creep. An example of this is documented on a slope instrumented with inclinometers and thermistors. Other slope movements related to pore pressure increases caused by active layer containment of unfrozen groundwater flows will be discussed. The impact of solifluction zones on pipeline construction and routing will be addressed as it has been managed along the TAPS. Other near surface slope movements that appear to be similar to solifluction have been observed along the pipeline right-of-way on the workpad. This paper will address an interrelationship of these observed slope behaviors. In doing this the interaction of slope seeps and the freeze front as it forms in fall and then recedes in spring and summer is compared to observations of engineered projects. Icings can be observed in several locations along TAPS. In some cases these can be related to slope movements. In other cases the icings have reached the aboveground and caused maintenance issues. TAPS was designed to avoid future surges of several large glaciers. In most years these glaciers have retreated and have not been a significant issue. A recent large earthquake caused a landslide on the largest glacier near TAPS and resulted in some review of the activity on that glacier. In 2002 a large earthquake centered near TAPS caused liquefaction in some areas, breakage of ice in lakes in some locations, and sand boils very close to the pipe. These observations will be related to the thinly frozen active layer over a deep talik during the earthquake.

Watershed Hydrology and Chemistry in the Alaskan Boreal Forest: The Central Role of Permafrost

2006 ◽  
Author(s):  
Larry D. Hinzman ◽  
Kevin C. Petrone
Keyword(s):  
Boreal Forest ◽  
Active Layer ◽  
Hydrological Processes ◽  
Organic Layer ◽  
Freezing And Thawing ◽  
Surface Soils ◽  
Near Surface ◽  
Organic Layers ◽  
Discontinuous Permafrost ◽  
Permafrost Soils

Hydrological processes exert strong control over biological and climatic processes in every ecosystem. They are particularly important in the boreal zone, where the average annual temperatures of the air and soil are relatively near the phase-change temperature of water (Chapter 4). Boreal hydrology is strongly controlled by processes related to freezing and thawing, particularly the presence or absence of permafrost. Flow in watersheds underlain by extensive permafrost is limited to the near-surface active layer and to small springs that connect the surface with the subpermafrost groundwater. Ice-rich permafrost, near the soil surface, impedes infiltration, resulting in soils that vary in moisture content from wet to saturated. Interior Alaska has a continental climate with relatively low precipitation (Chapter 4). Soils are typically aeolian or alluvial (Chapter 3). Consequently, in the absence of permafrost, infiltration is relatively high, yielding dry surface soils. In this way, discontinuous permafrost distribution magnifies the differences in soil moisture that might normally occur along topographic gradients. Hydrological processes in the boreal forest are unique due to highly organic soils with a porous organic mat on the surface, short thaw season, and warm summer and cold winter temperatures. The surface organic layer tends to be much thicker on north-facing slopes and in valley bottoms than on south-facing slopes and ridges, reflecting primarily the distribution of permafrost. Soils are cooler and wetter above permafrost, which retards decomposition, resulting in organic matter accumulation (Chapter 15). The markedly different material properties of the soil layers also influence hydrology. The highly porous near-surface soils allow rapid infiltration and, on hillsides, downslope drainage. The organic layer also has a relatively low thermal conductivity, resulting in slow thaw below thick organic layers. The thick organic layer limits the depth of thaw each summer to about 50–100 cm above permafrost (i.e., the active layer). As the active layer thaws, the hydraulic properties change. For example, the moisture-holding capacity increases, and additional subsurface layers become available for lateral flow. The mosaic of Alaskan vegetation depends not only on disturbance history (Chapter 7) but also on hydrology (Chapter 6).

scholarly journals Impact of river channel lateral migration on microbial communities across a discontinuous permafrost floodplain

2021 ◽  
Author(s):  
Madison M. Douglas ◽  
Usha F. Lingappa ◽  
Michael P. Lamb ◽  
Joel C. Rowland ◽  
A. Joshua West ◽  
...  
Keyword(s):  
Microbial Communities ◽  
Active Layer ◽  
River Channel ◽  
Rrna Gene ◽  
Lateral Migration ◽  
Channel Migration ◽  
Near Surface ◽  
Permafrost Thaw ◽  
Discontinuous Permafrost ◽  
River Migration

Permafrost soils store approximately twice the amount of carbon currently present in Earth’s atmosphere and are acutely impacted by climate change due to the polar amplification of increasing global temperature. Many organic-rich permafrost sediments are located on large river floodplains, where river channel migration periodically erodes and re-deposits the upper tens of meters of sediment. Channel migration exerts a first-order control on the geographic distribution of permafrost and floodplain stratigraphy and thus may affect microbial habitats. To examine how river channel migration in discontinuous permafrost environments affects microbial community composition, we used amplicon sequencing of the 16S rRNA gene on sediment samples from floodplain cores and exposed riverbanks along the Koyukuk River, a large tributary of the Yukon River in west-central Alaska. Microbial communities are sensitive to permafrost thaw: communities found in deep samples thawed by the river closely resembled near-surface active layer communities in non-metric multidimensional scaling analyses but did not resemble floodplain permafrost communities at the same depth. Microbial communities also displayed lower diversity and evenness in permafrost than in both the active layer and permafrost-free point bars recently deposited by river channel migration. Taxonomic assignments based on 16S and quantitative PCR for the methyl-coenzyme M reductase functional gene demonstrated that methanogens and methanotrophs are abundant in older permafrost-bearing deposits, but not in younger, non-permafrost point bar deposits. The results suggested that river migration, which regulates the distribution of permafrost, also modulates the distribution of microbes potentially capable of producing and consuming methane on the Koyukuk River floodplain. Importance Arctic lowlands contain large quantities of soil organic carbon that is currently sequestered in permafrost. With rising temperatures, permafrost thaw may allow this carbon to be consumed by microbial communities and released to the atmosphere as carbon dioxide or methane. We used gene sequencing to determine the microbial communities present in the floodplain of a river running through discontinuous permafrost. We found the river’s lateral movement across its floodplain influences the occurrence of certain microbial communities—in particular, methane-cycling microbes were present on the older, permafrost-bearing eroding riverbank but absent on the newly deposited river bars. Riverbank sediment had microbial communities more similar to the floodplain active layer than permafrost samples from the same depth. Therefore, spatial patterns of river migration influence the distribution of microbial taxa relevant to the warming Arctic climate.

scholarly journals Impact of model developments on present and future simulations of permafrost in a global land-surface model

2015 ◽  
Vol 9 (4) ◽  
pp. 1505-1521 ◽  
Author(s):  
S. E. Chadburn ◽  
E. J. Burke ◽  
R. L. H. Essery ◽  
J. Boike ◽  
M. Langer ◽  
...  
Keyword(s):  
Active Layer ◽  
Land Surface ◽  
Future Climate ◽  
Organic Soils ◽  
Surface Model ◽  
Permafrost Degradation ◽  
Microbial Decomposition ◽  
Near Surface ◽  
Model Version ◽  
The Impact

Abstract. There is a large amount of organic carbon stored in permafrost in the northern high latitudes, which may become vulnerable to microbial decomposition under future climate warming. In order to estimate this potential carbon–climate feedback it is necessary to correctly simulate the physical dynamics of permafrost within global Earth system models (ESMs) and to determine the rate at which it will thaw. Additional new processes within JULES, the land-surface scheme of the UK ESM (UKESM), include a representation of organic soils, moss and bedrock and a modification to the snow scheme; the sensitivity of permafrost to these new developments is investigated in this study. The impact of a higher vertical soil resolution and deeper soil column is also considered. Evaluation against a large group of sites shows the annual cycle of soil temperatures is approximately 25 % too large in the standard JULES version, but this error is corrected by the model improvements, in particular by deeper soil, organic soils, moss and the modified snow scheme. A comparison with active layer monitoring sites shows that the active layer is on average just over 1 m too deep in the standard model version, and this bias is reduced by 70 cm in the improved version. Increasing the soil vertical resolution allows the full range of active layer depths to be simulated; by contrast, with a poorly resolved soil at least 50 % of the permafrost area has a maximum thaw depth at the centre of the bottom soil layer. Thus all the model modifications are seen to improve the permafrost simulations. Historical permafrost area corresponds fairly well to observations in all simulations, covering an area between 14 and 19 million km2. Simulations under two future climate scenarios show a reduced sensitivity of permafrost degradation to temperature, with the near-surface permafrost loss per degree of warming reduced from 1.5 million km2 °C−1 in the standard version of JULES to between 1.1 and 1.2 million km2 °C−1 in the new model version. However, the near-surface permafrost area is still projected to approximately half by the end of the 21st century under the RCP8.5 scenario.

The response (1958-1997) of permafrost and near-surface ground temperatures to forest fire, Takhini River valley, southern Yukon Territory

1998 ◽  
Vol 35 (2) ◽  
pp. 184-199 ◽  
Author(s):  
C R Burn
Keyword(s):  
Active Layer ◽  
Forest Fires ◽  
Ground Surface ◽  
Yukon Territory ◽  
River Valley ◽  
Permafrost Degradation ◽  
Near Surface ◽  
Surface Conditions ◽  
Mean Temperature ◽  
Discontinuous Permafrost

Forest fires in permafrost areas often modify ground surface conditions, causing deepening of the active layer and thawing of near-surface permafrost. Takhini River valley lies in the discontinuous permafrost zone of southern Yukon Territory. The valley floor is covered by glaciolacustrine deposits, which are locally ice rich. In 1958 extensive forest fires burned most of the vegetation and the soil organic horizon in the valley, but, 50 km west of Whitehorse, 1 km2 of spruce forest adjacent to the Alaska Highway escaped burning. Permafrost beneath this stand of trees is in equilibrium with surface conditions: the active layer is 1.4 m thick, the base of permafrost is at 18.5 m, the annual mean temperature at the top of permafrost (1.5 m) is -0.8°C, and the temperature gradient in permafrost is constant with depth. At burned sites nearby there has been little regeneration of forest vegetation since the fire, and long-term permafrost degradation has occurred. At one burned site, the permafrost table is more than 3.75 m below the ground surface, the mean annual ground temperature is -0.2°C or warmer throughout the profile, the annual mean temperature at 1.5 m is 0.1°C, and permafrost is thawing from top and bottom. A simplified analytical model for thawing of permafrost indicates that over a millennium will be required to degrade permafrost completely at this site, if thawing proceeds from the top down. The result demonstrates the persistence of ice-rich permafrost a few metres below the ground surface, even at sites near the southern margin of permafrost in Canada.

scholarly journals Impact of model developments on present and future simulations of permafrost in a global land-surface model

2015 ◽  
Vol 9 (2) ◽  
pp. 1965-2012 ◽  
Author(s):  
S. E. Chadburn ◽  
E. J. Burke ◽  
R. L. H. Essery ◽  
J. Boike ◽  
M. Langer ◽  
...  
Keyword(s):  
Active Layer ◽  
Land Surface ◽  
Future Climate ◽  
Organic Soils ◽  
Surface Model ◽  
Permafrost Degradation ◽  
Microbial Decomposition ◽  
Near Surface ◽  
Model Version ◽  
The Impact

Abstract. There is a large amount of organic carbon stored in permafrost in the northern high latitudes, which may become vulnerable to microbial decomposition under future climate warming. In order to estimate this potential carbon-climate feedback it is necessary to correctly simulate the physical dynamics of permafrost within global Earth System Models (ESMs) and to determine the rate at which it will thaw. Additional new processes within JULES, the land surface scheme of the UK ESM (UKESM), include a representation of organic soils, moss and bedrock, and a modification to the snow scheme. The impact of a higher vertical soil resolution and deeper soil column is also considered. Evaluation against a large group of sites shows the annual cycle of soil temperatures is approximately 25 % too large in the standard JULES version, but this error is corrected by the model improvements, in particular by deeper soil, organic soils, moss and the modified snow scheme. Comparing with active layer monitoring sites shows that the active layer is on average just over 1 m too deep in the standard model version, and this bias is reduced by 70 cm in the improved version. Increasing the soil vertical resolution allows the full range of active layer depths to be simulated, where by contrast with a poorly resolved soil, at least 50% of the permafrost area has a maximum thaw depth at the centre of the bottom soil layer. Thus all the model modifications are seen to improve the permafrost simulations. Historical permafrost area corresponds fairly well to observations in all simulations, covering an area between 14–19 million km2. Simulations under two future climate scenarios show a reduced sensitivity of permafrost degradation to temperature, with the near-surface permafrost lost per degree of warming reduced from 1.5 million km2 °C−1 in the standard version of JULES to between 1.1 and 1.2 million km2 °C−1 in the new model version. However, the near-surface permafrost area is still projected to approximately half by the end of the 21st century under the RCP8.5 scenario.

scholarly journals Impact of permafrost thaw on the turbidity regime of a subarctic river: the Sheldrake River, Nunavik, Quebec

2017 ◽  
Vol 3 (2) ◽  
pp. 451-474 ◽  
Author(s):  
Maxime Jolivel ◽  
Michel Allard
Keyword(s):  
Active Layer ◽  
River Flow ◽  
High Water ◽  
Sediment Delivery ◽  
Discontinuous Permafrost ◽  
Level Data ◽  
Water Level Data ◽  
Water Stage ◽  
Rain Events ◽  
The Impact

In order to assess the impact of seasonal active layer thaw and thermokarst on river flow and turbidity, a gauging station was installed near the mouth of the Sheldrake River in the discontinuous permafrost zone of northern Quebec. The station provided 5 years of water level data and 3 years of turbidity data. The hydrological data for the river showed the usual high water stage occurring at spring snowmelt, with smaller peaks related to rain events in summer. Larger and longer turbidity peaks also occurred in summer in response to warm air temperature spells, suggesting that a large part of the annual suspension load was carried during midsummer turbidity peaks. Supported by geomorphological observations across the catchment area, the most plausible interpretation is that the rapid thawing of the active layer during warm conditions in July led to the activation of frostboils and triggered landslides throughout the river catchment, thus increasing soil erosion and raising sediment delivery into the hydrological network. These results indicate that maximum sediment discharge in a thermokarst-affected region may be predominantly driven by the rate of summer thawing and associated activation of erosion features in the catchment.

A Method for Evaluating Intensity of Water Cavitation Peening Processing

2011 ◽  
Vol 675-677 ◽  
pp. 747-750
Author(s):  
B. Han ◽  
Dong Ying Ju ◽  
Xiao Guang Yu
Keyword(s):  
Residual Stress ◽  
Process Capability ◽  
Diffraction Method ◽  
Spring Steel ◽  
Bubble Collapse ◽  
Plastic Layer ◽  
Process Conditions ◽  
X Ray Diffraction ◽  
Near Surface ◽  
The Impact

Water cavitation peening (WCP) with aeration, namely, a new ventilation nozzle with aeration is adopted to improve the process capability of WCP by increasing the impact pressure induced by the bubble collapse on the surface of components. In this study, in order to investigate the process capability of the WCP with aeration a standard N-type almen strips of spring steel SAE 1070 was treated byWCP with various process conditions, and the arc height value and the residual stress in the superficial layers were measured by means of the Almen-scale and X-ray diffraction method, respectively. The optimal fluxes of aeration and the optimal standoff distances were achieved. The maximum of arc height value reach around 150μm. The depth of plastic layer observed from the results of residual stresses is up to 150μm. The results verify the existence of macro-plastic strain in WCP processing. The distributions of residual stress in near-surface under different peening intensity can provide a reference for engineers to decide the optimal process conditions of WCP processing.

scholarly journals Assessing the regional impacts of Mexico City emissions on air quality and chemistry

2009 ◽  
Vol 9 (11) ◽  
pp. 3731-3743 ◽  
Author(s):  
M. Mena-Carrasco ◽  
G. R. Carmichael ◽  
J. E. Campbell ◽  
D. Zimmerman ◽  
Y. Tang ◽  
...  
Keyword(s):  
Air Quality ◽  
Mexico City ◽  
Ozone Production ◽  
Anthropogenic Aerosol ◽  
Near Surface ◽  
Mixing Ratios ◽  
Regional Impacts ◽  
Photolysis Rates ◽  
Regional Air Quality ◽  
The Impact

Abstract. The impact of Mexico City (MCMA) emissions is examined by studying its effects on air quality, photochemistry, and on ozone production regimes by combining model products and aircraft observations from the MILAGRO experiment during March 2006. The modeled influence of MCMA emissions to enhancements in surface level NOx, CO, and O3 concentrations (10–30% increase) are confined to distances <200 km, near surface. However, the extent of the influence is significantly larger at higher altitudes. Broader MCMA impacts (some 900 km Northeast of the city) are shown for specific outflow conditions in which enhanced ozone, NOy, and MTBE mixing ratios over the Gulf of Mexico are linked to MCMA by source tagged tracers and sensitivity runs. This study shows that the "footprint" of MCMA on average is fairly local, with exception to reactive nitrogen, which can be transported long range in the form of PAN, acting as a reservoir and source of NOx with important regional ozone formation implications. The simulated effect of MCMA emissions of anthropogenic aerosol on photochemistry showed a maximum regional decrease of 40% in J[NO2→NO+O], and resulting in the reduction of ozone production by 5–10%. Observed ozone production efficiencies are evaluated as a function of distance from MCMA, and by modeled influence from MCMA. These tend to be much lower closer to MCMA, or in those points where modeled contribution from MCMA is large. This research shows that MCMA emissions do effect on regional air quality and photochemistry, both contributing large amounts of ozone and its precursors, but with caveat that aerosol concentrations hinder formation of ozone to its potential due to its reduction in photolysis rates.

scholarly journals The Impact of Finer-Resolution Air–Sea Coupling on the Intraseasonal Oscillation of the Indian Monsoon

2011 ◽  
Vol 24 (10) ◽  
pp. 2451-2468 ◽  
Author(s):  
Nicholas P. Klingaman ◽  
Steven J. Woolnough ◽  
Hilary Weller ◽  
Julia M. Slingo
Keyword(s):  
Atmospheric Stability ◽  
Intraseasonal Oscillation ◽  
Boreal Summer ◽  
Upper Ocean ◽  
Vertical Resolution ◽  
Coupled Models ◽  
Diurnal Variability ◽  
Near Surface ◽  
The Impact ◽  
Coupling Frequency

Abstract A newly assembled atmosphere–ocean coupled model, called HadKPP, is described and then used to determine the effects of subdaily air–sea coupling and fine near-surface ocean vertical resolution on the representation of the Northern Hemisphere summer intraseasonal oscillation. HadKPP comprises the Hadley Centre atmospheric model coupled to the K-Profile Parameterization ocean boundary layer model. Four 30-member ensembles were performed that vary in ocean vertical resolution between 1 and 10 m and in coupling frequency between 3 and 24 h. The 10-m, 24-h ensemble exhibited roughly 60% of the observed 30–50-day variability in sea surface temperatures and rainfall and very weak northward propagation. Enhancing only the vertical resolution or only the coupling frequency produced modest improvements in variability and just a standing intraseasonal oscillation. Only the 1-m, 3-h configuration generated organized, northward-propagating convection similar to observations. Subdaily surface forcing produced stronger upper-ocean temperature anomalies in quadrature with anomalous convection, which likely affected lower-atmospheric stability ahead of the convection, causing propagation. Well-resolved air–sea coupling did not improve the eastward propagation of the boreal summer intraseasonal oscillation in this model. Upper-ocean vertical mixing and diurnal variability in coupled models must be improved to accurately resolve and simulate tropical subseasonal variability. In HadKPP, the mere presence of air–sea coupling was not sufficient to generate an intraseasonal oscillation resembling observations.

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