scholarly journals Three-Dimensional Stefan Equation for Thermokarst Lake and Talik Geometry Characterization

2021 ◽  
Author(s):  
Noriaki Ohara ◽  
Benjamin M. Jones ◽  
Andrew D. Parsekian ◽  
Kenneth M. Hinkel ◽  
Katsu Yamatani ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Ground Subsidence ◽  
The Arctic ◽  
Permafrost Region ◽  
Boundary Area ◽  
Near Surface ◽  
Thermokarst Lakes ◽  
Thermokarst Lake ◽  
Permafrost Thaw ◽  
Transient Electromagnetic

Abstract. Thermokarst lake dynamics, which plays an essential role in carbon release due to permafrost thaw, is affected by various geomorphological processes. In this study, we derive a three-dimensional (3D) Stefan equation to characterize talik geometry under a hypothetical thermokarst lake in the continuous permafrost region. Using the Euler equation in the calculus of variations, the lower bounds of the talik were determined as an extremum of the functional describing the phase boundary area with a fixed total talik volume. We demonstrate that the semi-ellipsoid geometry of the talik is optimal for minimizing the total permafrost thaw under the lake for a given annual heat supply. The model predicting ellipsoidal talik geometry was verified by talik thickness observations using transient electromagnetic (TEM) soundings in Peatball Lake on the Arctic Coastal Plain (ACP) of Alaska. The lake width-depth ratio of the elliptic talik can characterize the energy flux anisotropy in the permafrost although the lake bathymetry cross section may not be elliptic due to the presence of near-surface ice-rich permafrost. This theory suggests that talik development stabilizes thermokarst lakes by ground subsidence due to permafrost thaw while wind-induced waves and currents are likely responsible for the elongation and orientation of thermokarst lakes in certain regions such as the ACP of northern Alaska.

scholarly journals Population living on permafrost in the Arctic

2021 ◽  
Vol 43 (1) ◽  
pp. 22-38
Author(s):  
Justine Ramage ◽  
Leneisja Jungsberg ◽  
Shinan Wang ◽  
Sebastian Westermann ◽  
Hugues Lantuit ◽  
...  
Keyword(s):  
The Arctic ◽  
Permafrost Region ◽  
Permafrost Thaw ◽  
Arctic Regions ◽  
High Hazard

AbstractPermafrost thaw is a challenge in many Arctic regions, one that modifies ecosystems and affects infrastructure and livelihoods. To date, there have been no demographic studies of the population on permafrost. We present the first estimates of the number of inhabitants on permafrost in the Arctic Circumpolar Permafrost Region (ACPR) and project changes as a result of permafrost thaw. We combine current and projected populations at settlement level with permafrost extent. Key findings indicate that there are 1162 permafrost settlements in the ACPR, accommodating 5 million inhabitants, of whom 1 million live along a coast. Climate-driven permafrost projections suggest that by 2050, 42% of the permafrost settlements will become permafrost-free due to thawing. Among the settlements remaining on permafrost, 42% are in high hazard zones, where the consequences of permafrost thaw will be most severe. In total, 3.3 million people in the ACPR live currently in settlements where permafrost will degrade and ultimately disappear by 2050.

Interpretation of 3-D effects in long‐offset transient electromagnetic (LOTEM) soundings in the Münsterland area/Germany

Geophysics ◽  
1992 ◽  
Vol 57 (9) ◽  
pp. 1127-1137 ◽  
Author(s):  
Andreas Hördt ◽  
Vladimir L. Druskin ◽  
Leonid A. Knizhnerman ◽  
Kurt‐Martin Strack
Keyword(s):  
Integral Equation ◽  
Thin Sheet ◽  
Three Dimensional ◽  
Equation Modeling ◽  
Data Sets ◽  
Sign Reversal ◽  
Near Surface ◽  
Transient Electromagnetic ◽  
Long Offset ◽  
Geological Situation

The interpretation of long‐offset transient electromagnetic (LOTEM) data is usually based on layered earth models. Effects of lateral conductivity variations are commonly explained qualitatively, because three‐dimensional (3-D) numerical modeling is not readily available for complex geology. One of the first quantitative 3-D interpretations of LOTEM data is carried out using measurements from the Münsterland basin in northern Germany. In this survey area, four data sets show effects of lateral variations including a sign reversal in the measured voltage curve at one site. This sign reversal is a clear indicator of two‐dimensional (2-D) or 3-D conductivity structure, and can be caused by current channeling in a near‐surface conductive body. Our interpretation strategy involves three different 3-D forward modeling programs. A thin‐sheet integral equation modeling routine used with inversion gives a first guess about the location and strike of the anomaly. A volume integral equation program allows models that may be considered possible geological explanations for the conductivity anomaly. A new finite‐difference algorithm permits modeling of much more complex conductivity structures for simulating a realistic geological situation. The final model has the zone of anomalous conductivity aligned below a creek system at the surface. Since the creeks flow along weak zones in this area, the interpretation seems geologically reasonable. The interpreted model also yields a good fit to the data.

scholarly journals Reviews and Syntheses: Effects of permafrost thaw on arctic aquatic ecosystems

2015 ◽  
Vol 12 (13) ◽  
pp. 10719-10815 ◽  
Author(s):  
J. E. Vonk ◽  
S. E. Tank ◽  
W. B. Bowden ◽  
I. Laurion ◽  
W. F. Vincent ◽  
...  
Keyword(s):  
Organic Matter ◽  
Aquatic Ecosystems ◽  
Soil Layer ◽  
Freshwater Ecosystems ◽  
The Arctic ◽  
Food Web Structure ◽  
Thermokarst Lakes ◽  
Freshwater Systems ◽  
Permafrost Thaw ◽  
Lake Morphology

Abstract. The Arctic is a water-rich region, with freshwater systems covering 16 % of the northern permafrost landscape. The thawing of this permafrost creates new freshwater ecosystems, while at the same time modifying the existing lakes, streams, and rivers that are impacted by thaw. Here, we describe the current state of knowledge regarding how permafrost thaw affects lentic and lotic systems, exploring the effects of both thermokarst (thawing and collapse of ice-rich permafrost) and deepening of the active layer (the surface soil layer that thaws and refreezes each year). Within thermokarst, we further differentiate between the effects of thermokarst in lowland areas, vs. that on hillslopes. For almost all of the processes that we explore, the effects of thaw vary regionally, and between lake and stream systems. Much of this regional variation is caused by differences in ground ice content, topography, soil type, and permafrost coverage. Together, these modifying variables determine the degree to which permafrost thaw manifests as thermokarst, whether thermokarst leads to slumping or the formation of thermokarst lakes, and the manner in which constituent delivery to freshwater systems is altered by thaw. Differences in thaw-enabled constituent delivery can be considerable, with these modifying variables determining, for example, the balance between delivery of particulate vs. dissolved constituents, and inorganic vs. organic materials. Changes in the composition of thaw-impacted waters, coupled with changes in lake morphology, can strongly affect the physical and optical properties of thermokarst lakes. The ecology of thaw-impacted systems is also likely to change, with thaw-impacted lakes and streams having unique microbiological communities, and showing differences in respiration, primary production, and food web structure that are largely driven by differences in sediment, dissolved organic matter and nutrient delivery. The degree to which thaw enables the delivery of dissolved vs. particulate organic matter, coupled with the composition of that organic matter and the morphology and stratification characteristics of recipient systems will play an important role in determining the balance between the release of organic matter as greenhouse gases (CO2 and CH4), its burial in sediments, and its loss downstream. The magnitude of thaw impacts on northern aquatic ecosystems is increasing, as is the prevalence of thaw-impacted lakes and streams. There is therefore an urgent need to address the key gaps in understanding in order to predict the full effects of permafrost thaw on aquatic ecosystems throughout the Arctic, and their consequential feedbacks to climate.

scholarly journals Effects of multi-scale heterogeneity on the simulated evolution of ice-rich permafrost lowlands under a warming climate

2020 ◽  
Author(s):  
Jan Nitzbon ◽  
Moritz Langer ◽  
Léo C. P. Martin ◽  
Sebastian Westermann ◽  
Thomas Schneider von Deimling ◽  
...  
Keyword(s):  
Landscape Evolution ◽  
Spatial Scales ◽  
Ground Subsidence ◽  
The Arctic ◽  
Subgrid Scale ◽  
Multi Scale ◽  
Permafrost Thaw ◽  
Warming Climate ◽  
Ice Wedge ◽  
Meso Scale

Abstract. Thawing of ice-rich permafrost deposits can cause the formation of thermokarst terrain, thereby involving ground subsidence and feedbacks to the thermal and hydrological regimes of the subsurface. Thermokarst activity can entail manifold pathways of landscape evolution and cause rapid permafrost thaw in response to a warming climate. Numerical models that realistically capture these degradation pathways and represent the involved feedback processes at different spatial scales, are required to assess the threats and risks that thermokarst processes pose to the functioning of ecosystems and human infrastructure in the Arctic. In this study, we therefore introduce a multi-scale tiling scheme to the CryoGrid 3 permafrost model which allows to represent the spatial heterogeneities of surface and subsurface conditions, together with lateral fluxes of heat, water, snow, and sediment, at spatial scales not resolved in Earth system models (ESMs). We applied the model setup to a lowland tundra landscape in northeast Siberia characterized by ice-wedge polygons at various degradation stages. We present numerical simulations under a climate-warming scenario and investigate the sensitivity of projected permafrost thaw to different terrain heterogeneities, on both a micro-scale (ice-wedge polygons) and a meso-scale (low-gradient slopes). We found that accounting for both micro- and meso-scale heterogeneities yields the most realistic possibilities for simulating landscape evolution. Simulations that ignored one or the other of these scales of heterogeneity were unable to represent all of the possible spatio-temporal feedbacks in ice-rich terrain. For example, we show that the melting of ice wedges in one part of the landscape can result in the drainage of other parts, where surface water has been impounded a number of decades earlier as a result of ice-wedge thermokarst. We also found that including subgrid-scale heterogeneities in the simulations resulted in a more gradual response in terms of ground subsidence and permafrost thaw, compared to the more abrupt changes in simple one-dimensional simulations. Our results suggest that, under a warming climate, the investigated area is more likely to experience widespread drainage of polygonal wetlands than the formation of new thaw lakes, which is in general agreement with evidence from previous field studies. We also discuss how the presented model framework is able to capture a broad range of processes involved in the cycles of ice-wedge and thaw-lake evolution. The results of this study improve our understanding of how micro- and meso-scale processes control the evolution of ice-rich permafrost landscapes. Furthermore, the methods that we have developed allow improved representation of subgrid-scale processes such as thermokarst in ESMs.

scholarly journals Complex Vulnerabilities of the Water and Aquatic Carbon Cycles to Permafrost Thaw

2021 ◽  
Vol 3 ◽  
Author(s):  
Michelle A. Walvoord ◽  
Robert G. Striegl
Keyword(s):  
Water Cycle ◽  
The Arctic ◽  
Inland Waters ◽  
Polar Regions ◽  
Intergovernmental Panel ◽  
Near Surface ◽  
Carbon Cycles ◽  
Landscape Characteristics ◽  
Permafrost Thaw ◽  
Flow Surface

The spatial distribution and depth of permafrost are changing in response to warming and landscape disturbance across northern Arctic and boreal regions. This alters the infiltration, flow, surface and subsurface distribution, and hydrologic connectivity of inland waters. Such changes in the water cycle consequently alter the source, transport, and biogeochemical cycling of aquatic carbon (C), its role in the production and emission of greenhouse gases, and C delivery to inland waters and the Arctic Ocean. Responses to permafrost thaw across heterogeneous boreal landscapes will be neither spatially uniform nor synchronous, thus giving rise to expressions of low to medium confidence in predicting hydrologic and aquatic C response despite very high confidence in projections of widespread near-surface permafrost disappearance as described in the 2019 Intergovernmental Panel on Climate Change Special Report on the Ocean and Cryosphere in a Changing Climate: Polar Regions. Here, we describe the state of the science regarding mechanisms and factors that influence aquatic C and hydrologic responses to permafrost thaw. Through synthesis of recent topical field and modeling studies and evaluation of influential landscape characteristics, we present a framework for assessing vulnerabilities of northern permafrost landscapes to specific modes of thaw affecting local to regional hydrology and aquatic C biogeochemistry and transport. Lastly, we discuss scaling challenges relevant to model prediction of these impacts in heterogeneous permafrost landscapes.

scholarly journals Recent degradation of Interior Alaska permafrost mapped with ground surveys, geophysics, deep drilling, and repeat airborne LiDAR

2021 ◽  
Author(s):  
Thomas A. Douglas ◽  
Christopher A. Hiemstra ◽  
John E. Anderson ◽  
Robyn A. Barbato ◽  
Kevin L. Bjella ◽  
...  
Keyword(s):  
Active Layer ◽  
Climate Warming ◽  
Airborne Lidar ◽  
The Arctic ◽  
Permafrost Degradation ◽  
Top Down ◽  
Bottom Up ◽  
Near Surface ◽  
Permafrost Thaw ◽  
Tussock Tundra

Abstract. Permafrost underlies one quarter of the northern hemisphere but is at increasing risk of thaw from climate warming. Recent studies across the Arctic have identified areas of rapid permafrost degradation from both top-down and lateral thaw. Of particular concern is thawing of ice rich high carbon content syngenetic yedoma permafrost like much of the permafrost in the region around Fairbanks, Alaska. With a mean annual temperature of −2 °C subtle differences in ecotype and permafrost ice and soil content control the near-surface permafrost thermal regime. Long-term measurements of the seasonally thawed active layer across central Alaska have identified an increase in permafrost thaw degradation that is expected to continue, and even accelerate, in coming decades. A major knowledge gap is relating belowground measurements of seasonal thaw, permafrost characteristics, and talik development with aboveground ecotype properties and thermokarst expansion that can readily quantify vegetation cover and track surface elevation changes over time. This study was conducted from 2013–2020 along four 400 to 500 m long transects near Fairbanks, Alaska. Repeat end of season active layer depths, near-surface permafrost temperature measurements, electrical resistivity tomography (ERT), deep (> 5 m) boreholes, and repeat airborne LiDAR were used to measure top down thaw and map thermokarst development at the sites. Our study confirms previous work using ERT to map surface thawed zones, however, our deep boreholes confirm the boundaries between frozen and thawed zones that are needed to model top down, lateral, and bottom-up thaw. At disturbed sites seasonal thaw increased up to 25 % between mid-August and early October and suggests active layer depths must be made as late in the fall season as possible because the projected increase in the summer season of just a few weeks could lead to significant additional thaw. At our sites, tussock tundra and spruce forest are associated with the lowest mean annual near-surface permafrost temperatures while mixed forest ecotypes are the warmest and exhibit the highest degree of recent temperature warming and thaw degradation. Thermokarst features and perennially thawed zones (taliks) have been identified at all sites. Our measurements, when combined with longer-term records from yedoma across the 500,000 km2 area of central Alaska show widespread initiation of near-surface permafrost thaw since roughly 2010. Using this partial area of the yedoma domain and projecting our thaw depth increases, by ecotype, across this domain we calculate 0.44 Gt of permafrost soil C have been thawed over the 7 year period, an amount equal to the yearly CO2 emissions of Australia. Since the yedoma permafrost and the variety of ecotypes at our sites represent much of the Arctic and subarctic land cover this study shows remote sensing measurements, top-down and bottom-up thermal modelling, and ground based surveys can be used predictively to identify areas of highest risk for permafrost thaw from projected future climate warming.

scholarly journals Three-phase numerical model for subsurface hydrology in permafrost-affected regions

2014 ◽  
Vol 8 (1) ◽  
pp. 149-185 ◽  
Author(s):  
S. Karra ◽  
S. L. Painter ◽  
P. C. Lichtner
Keyword(s):  
Reactive Transport ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
The Arctic ◽  
Freezing And Thawing ◽  
Subsurface Hydrology ◽  
Near Surface ◽  
Three Phase ◽  
Dimensional Simulation ◽  
New Formulation

Abstract. Degradation of near-surface permafrost due to changes in the climate is expected to impact the hydrological, ecological and biogeochemical responses of the Arctic tundra. From a hydrological perspective, it is important to understand the movement of the various phases of water (gas, liquid and ice) during the freezing and thawing of near surface soils. We present a new non-isothermal, single-component (water), three-phase formulation that treats air as an inactive component. The new formulation is implemented in the massively parallel subsurface flow and reactive transport code PFLOTRAN. Parallel performance for this implementation is demonstrated, and validation studies using previously published experimental data are performed. A comparison between the new model and a more complete two-component (air–water) multiphase approach shows only minor differences. When water vapor diffusion is considered, a large effect on soil moisture dynamics is seen, which is due to dependence of thermal conductivity on ice content. A large three-dimensional simulation (with around 6 million degrees of freedom) of seasonal freezing and thawing is also presented.

scholarly journals Recent degradation of interior Alaska permafrost mapped with ground surveys, geophysics, deep drilling, and repeat airborne lidar

2021 ◽  
Vol 15 (8) ◽  
pp. 3555-3575
Author(s):  
Thomas A. Douglas ◽  
Christopher A. Hiemstra ◽  
John E. Anderson ◽  
Robyn A. Barbato ◽  
Kevin L. Bjella ◽  
...  
Keyword(s):  
Active Layer ◽  
Climate Warming ◽  
Airborne Lidar ◽  
The Arctic ◽  
Permafrost Degradation ◽  
Top Down ◽  
Bottom Up ◽  
Near Surface ◽  
Permafrost Thaw ◽  
Tussock Tundra

Abstract. Permafrost underlies one-quarter of the Northern Hemisphere but is at increasing risk of thaw from climate warming. Recent studies across the Arctic have identified areas of rapid permafrost degradation from both top-down and lateral thaw. Of particular concern is thawing syngenetic “yedoma” permafrost which is ice-rich and has a high carbon content. This type of permafrost is common in the region around Fairbanks, Alaska, and across central Alaska expanding westward to the Seward Peninsula. A major knowledge gap is relating belowground measurements of seasonal thaw, permafrost characteristics, and residual thaw layer development with aboveground ecotype properties and thermokarst expansion that can readily quantify vegetation cover and track surface elevation changes over time. This study was conducted from 2013 to 2020 along four 400 to 500 m long transects near Fairbanks, Alaska. Repeat active layer depths, near-surface permafrost temperature measurements, electrical resistivity tomography (ERT), deep (> 5 m) boreholes, and repeat airborne light detection and ranging (lidar) were used to measure top-down permafrost thaw and map thermokarst development at the sites. Our study confirms previous work using ERT to map surface thawed zones; however, our deep boreholes confirm the boundaries between frozen and thawed zones that are needed to model top-down, lateral, and bottom-up thaw. At disturbed sites seasonal thaw increased up to 25 % between mid-August and early October and suggests measurements to evaluate active layer depth must be made as late in the fall season as possible because the projected increase in the summer season of just a few weeks could lead to significant additional thaw. At our sites, tussock tundra and spruce forest are associated with the lowest mean annual near-surface permafrost temperatures while mixed-forest ecotypes are the warmest and exhibit the highest degree of recent temperature warming and thaw degradation. Thermokarst features, residual thaw layers, and taliks have been identified at all sites. Our measurements, when combined with longer-term records from yedoma across the 500 000 km2 area of central Alaska, show widespread near-surface permafrost thaw since 2010. Projecting our thaw depth increases, by ecotype, across the yedoma domain, we calculate a first-order estimate that 0.44 Pg of organic carbon in permafrost soil has thawed over the past 7 years, which, for perspective, is an amount of carbon nearly equal to the yearly CO2 emissions of Australia. Since the yedoma permafrost and the variety of ecotypes at our sites represent much of the Arctic and subarctic land cover, this study shows remote sensing measurements, top-down and bottom-up thermal modeling, and ground-based surveys can be used predictively to identify areas of the highest risk for permafrost thaw from projected future climate warming.

scholarly journals Three-phase numerical model for subsurface hydrology in permafrost-affected regions (PFLOTRAN-ICE v1.0)

2014 ◽  
Vol 8 (5) ◽  
pp. 1935-1950 ◽  
Author(s):  
S. Karra ◽  
S. L. Painter ◽  
P. C. Lichtner
Keyword(s):  
Reactive Transport ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Single Component ◽  
The Arctic ◽  
Freezing And Thawing ◽  
Subsurface Hydrology ◽  
Near Surface ◽  
Three Phase ◽  
Dimensional Simulation

Abstract. Degradation of near-surface permafrost due to changes in the climate is expected to impact the hydrological, ecological and biogeochemical responses of the Arctic tundra. From a hydrological perspective, it is important to understand the movement of the various phases of water (gas, liquid and ice) during the freezing and thawing of near-surface soils. We present a new non-isothermal, single-component (water), three-phase formulation that treats air as an inactive component. This single component model works well and produces similar results to a more complete and computationally demanding two-component (air, water) formulation, and is able to reproduce results of previously published laboratory experiments. A proof-of-concept implementation in the massively parallel subsurface flow and reactive transport code PFLOTRAN is summarized, and parallel performance of that implementation is demonstrated. When water vapor diffusion is considered, a large effect on soil moisture dynamics is seen, which is due to dependence of thermal conductivity on ice content. A large three-dimensional simulation (with around 6 million degrees of freedom) of seasonal freezing and thawing is also presented.

scholarly journals Reviews and syntheses: Effects of permafrost thaw on Arctic aquatic ecosystems

2015 ◽  
Vol 12 (23) ◽  
pp. 7129-7167 ◽  
Author(s):  
J. E. Vonk ◽  
S. E. Tank ◽  
W. B. Bowden ◽  
I. Laurion ◽  
W. F. Vincent ◽  
...  
Keyword(s):  
Organic Matter ◽  
Aquatic Ecosystems ◽  
Freshwater Ecosystems ◽  
The Arctic ◽  
Food Web Structure ◽  
Thermokarst Lakes ◽  
Freshwater Systems ◽  
Permafrost Thaw ◽  
Modifying Factors ◽  
Lake Morphology

Abstract. The Arctic is a water-rich region, with freshwater systems covering about 16 % of the northern permafrost landscape. Permafrost thaw creates new freshwater ecosystems, while at the same time modifying the existing lakes, streams, and rivers that are impacted by thaw. Here, we describe the current state of knowledge regarding how permafrost thaw affects lentic (still) and lotic (moving) systems, exploring the effects of both thermokarst (thawing and collapse of ice-rich permafrost) and deepening of the active layer (the surface soil layer that thaws and refreezes each year). Within thermokarst, we further differentiate between the effects of thermokarst in lowland areas vs. that on hillslopes. For almost all of the processes that we explore, the effects of thaw vary regionally, and between lake and stream systems. Much of this regional variation is caused by differences in ground ice content, topography, soil type, and permafrost coverage. Together, these modifying factors determine (i) the degree to which permafrost thaw manifests as thermokarst, (ii) whether thermokarst leads to slumping or the formation of thermokarst lakes, and (iii) the manner in which constituent delivery to freshwater systems is altered by thaw. Differences in thaw-enabled constituent delivery can be considerable, with these modifying factors determining, for example, the balance between delivery of particulate vs. dissolved constituents, and inorganic vs. organic materials. Changes in the composition of thaw-impacted waters, coupled with changes in lake morphology, can strongly affect the physical and optical properties of thermokarst lakes. The ecology of thaw-impacted lakes and streams is also likely to change; these systems have unique microbiological communities, and show differences in respiration, primary production, and food web structure that are largely driven by differences in sediment, dissolved organic matter, and nutrient delivery. The degree to which thaw enables the delivery of dissolved vs. particulate organic matter, coupled with the composition of that organic matter and the morphology and stratification characteristics of recipient systems will play an important role in determining the balance between the release of organic matter as greenhouse gases (CO2 and CH4), its burial in sediments, and its loss downstream. The magnitude of thaw impacts on northern aquatic ecosystems is increasing, as is the prevalence of thaw-impacted lakes and streams. There is therefore an urgent need to quantify how permafrost thaw is affecting aquatic ecosystems across diverse Arctic landscapes, and the implications of this change for further climate warming.

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