Contrasting extreme runoff events in areas of continuous permafrost, Arctic Alaska

Spring snowmelt floods in the Arctic are common and can be expected every year, mainly because of the extensive snow cover that ablates relatively quickly. However, documentation of extreme flows (both low and high) in the Arctic is lacking in part because extreme flows are relatively rare and gauging sites are very sparse, with most of short duration. In the nested Kuparuk River research watersheds on the North Slope of Alaska, two large summer floods have been observed (July 1999 and August 2002) in the headwaters; these high flows are contrasted to the low flows (drought conditions) observed in the summers of 2005 and 2007. It is clear that the continuous permafrost and the limited near-surface storage in the shallow active layer are responsible for both the high and low flow responses. Or, stated another way, the active layer is a poor buffer to both floods and droughts. When contrasting summer floods with snowmelt floods, it is clear from flood frequency analyses that the smaller, high-gradient headwater basins will be dominated by summer floods while those watersheds draining the low gradient coastal plain will be dominated by snowmelt floods. The two summer floods in the headwaters had flows that were three to four times greater than the largest measured snowmelt flood, while on the coastal plain the 2002 summer storm for the whole of the Kuparuk River only produced the maximum summer runoff of record that was about 1/4 of the maximum snowmelt flood. So, on the coastal plain and even for the Greater Kuparuk River that drains across the coastal plain, snowmelt floods dominate. Drought conditions prevail in summers when the limited surface water storage in the active layer and surface water bodies is depleted because evapotranspiration exceeds precipitation.

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Geophysical imaging of permafrost in the SW Svalbard – the result of two high arctic expeditions to Spitsbergen

10.5194/egusphere-egu2020-8136 ◽

2020 ◽

Author(s):

Mariusz Majdanski ◽

Artur Marciniak ◽

Bartosz Owoc ◽

Wojciech Dobiński ◽

Tomasz Wawrzyniak ◽

...

Keyword(s):

Surface Waves ◽

Active Layer ◽

High Arctic ◽

The Arctic ◽

Seismic Profiles ◽

Frozen Ground ◽

Near Surface ◽

Seismic Processing ◽

Reflection Seismic ◽

Sea Coast

The Arctic regions are the place of the fastest observed climate change. One of the indicators of such evolution are changes occurring in the glaciers and the subsurface in the permafrost. The active layer of the permafrost as the shallowest one is well measured by multiple geophysical techniques and in-situ measurements.Two high arctic expeditions have been organized to use seismic methods to recognize the shape of the permafrost in two seasons: with the unfrozen ground (October 2017) and frozen ground (April 2018). Two seismic profiles have been designed to visualize the shape of permafrost between the sea coast and the slope of the mountain, and at the front of a retreating glacier. For measurements, a stand-alone seismic stations has been used with accelerated weight drop with in-house modifications and timing system. Seismic profiles were acquired in a time-lapse manner and were supported with GPR and ERT measurements, and continuous temperature monitoring in shallow boreholes.Joint interpretation of seismic and auxiliary data using Multichannel analysis of surface waves, First arrival travel-time tomography and Reflection imaging show clear seasonal changes affecting the active layer where P-wave velocities are changing from 3500 to 5200 m/s. This confirms the laboratory measurements showing doubling the seismic velocity of water-filled high-porosity rocks when frozen. The same laboratory study shows significant (>10%) increase of velocity in frozen low porosity rocks, that should be easily visible in seismic.In the reflection seismic processing, the most critical part was a detailed front mute to eliminate refracted arrivals spoiling wide-angle near-surface reflections. Those long offset refractions were however used to estimate near-surface velocities further used in reflection processing. In the reflection seismic image, a horizontal reflection was traced at the depth of 120 m at the sea coast deepening to the depth of 300 m near the mountain.Additionally, an optimal set of seismic parameters has been established, clearly showing a significantly higher signal to noise ratio in case of frozen ground conditions even with the snow cover. Moreover, logistics in the frozen conditions are much easier and a lack of surface waves recorded in the snow buried geophones makes the seismic processing simpler.Acknowledgements&#160; &#160; &#160; &#160; &#160; &#160; &#160; &#160;This research was funded by the National Science Centre, Poland (NCN) Grant UMO-2015/21/B/ST10/02509.

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Spatial distribution of near surface soil moisture and its relationship to microtopography in the Alaskan Arctic coastal plain

Hydrology Research ◽

10.2166/nh.2005.0016 ◽

2005 ◽

Vol 36 (3) ◽

pp. 219-234 ◽

Cited By ~ 49

Author(s):

R. Engstrom ◽

A. Hope ◽

H. Kwon ◽

D. Stow ◽

D. Zamolodchikov

Keyword(s):

Soil Moisture ◽

Coastal Plain ◽

Surface Soil ◽

The Arctic ◽

Ground Vegetation ◽

Primary Control ◽

Surface Soil Moisture ◽

Substantial Impact ◽

Near Surface ◽

Arctic Coastal Plain

The Arctic coastal plain of Alaska is characterized by marked heterogeneity in microtopography and above ground vegetation productivity at a variety of scales. This heterogeneity may be expected to lead to large variations in near surface soil moisture and have a substantial impact on measured and modeled fluxes of carbon and water. In this study, we hypothesized that microtopography was the primary control over the spatial patterns of near surface soil moisture. Near surface soil moisture measurements were collected in the summers of 2000, 2001, 2002 and 2003 in the fetch of an eddy flux tower (0.5 km2). Results confirmed the expected relationship between intra- and inter-seasonal variations in near surface soil moisture and variations in precipitation. However, over two time periods, near surface soil moisture increased without corresponding measured precipitation inputs and this was attributed to fog and dew, which are difficult to measure, and/or the melting of the active layer. Spatial variations in near surface soil moisture are largely controlled by microtopography in areas characterized by high centered polygons and troughs. In areas without large variations in microtopography, macrotopography, in the form of drained thaw lakes, has a substantial control over near surface soil moisture.

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

10.5194/tc-2021-47 ◽

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.

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

The Cryosphere ◽

10.5194/tc-15-3555-2021 ◽

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.

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Comparison of MODIS-derived land surface temperatures with ground surface and air temperature measurements in continuous permafrost terrain

The Cryosphere ◽

10.5194/tc-6-51-2012 ◽

2012 ◽

Vol 6 (1) ◽

pp. 51-69 ◽

Cited By ~ 82

Author(s):

S. Hachem ◽

C. R. Duguay ◽

M. Allard

Keyword(s):

Surface Temperature ◽

Land Surface ◽

Ground Surface ◽

Surface Heterogeneity ◽

The Arctic ◽

Near Surface ◽

The North ◽

Continuous Permafrost ◽

Spatial Estimates ◽

Promising Source

Abstract. Obtaining high resolution records of surface temperature from satellite sensors is important in the Arctic because meteorological stations are scarce and widely scattered in those vast and remote regions. Surface temperature is the primary climatic factor that governs the existence, spatial distribution and thermal regime of permafrost which is a major component of the terrestrial cryosphere. Land Surface (skin) Temperatures (LST) derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor aboard the Terra and Aqua satellite platforms provide spatial estimates of near-surface temperature values. In this study, LST values from MODIS are compared to ground-based near-surface air (Tair) and ground surface temperature (GST) measurements obtained from 2000 to 2008 at herbaceous and shrub tundra sites located in the continuous permafrost zone of Northern Québec, Nunavik, Canada, and of the North Slope of Alaska, USA. LSTs (temperatures at the surface materials-atmosphere interface) are found to be better correlated with Tair (1–3 m above the ground) than with available GST (3–5 cm below the ground surface). As Tair is most often used by the permafrost community, this study focused on this parameter. LSTs are in stronger agreement with Tair during the snow cover season than in the snow free season. Combining Aqua and Terra LST-Day and LST-Nigh acquisitions into a mean daily value provides a large number of LST observations and a better overall agreement with Tair. Comparison between mean daily LSTs and mean daily Tair, for all sites and all seasons pooled together yields a very high correlation (R = 0.97; mean difference (MD) = 1.8 °C; and standard deviation of MD (SD) = 4.0 °C). The large SD can be explained by the influence of surface heterogeneity within the MODIS 1 km2 grid cells, the presence of undetected clouds and the inherent difference between LST and Tair. Retrieved over several years, MODIS LSTs offer a great potential for monitoring surface temperature changes in high-latitude tundra regions and are a promising source of input data for integration into spatially-distributed permafrost models.

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The impact of shallow stratification on air-sea CO2 flux in the summer Arctic Ocean

10.5194/egusphere-egu21-715 ◽

2021 ◽

Author(s):

Yuanxu Dong ◽

Dorothee Bakker ◽

Thomas Bell ◽

Peter Liss ◽

Ian Brown ◽

...

Keyword(s):

Surface Water ◽

Wind Speed ◽

Sea Ice ◽

Surface Temperature ◽

Arctic Ocean ◽

The Arctic ◽

Near Surface ◽

Ice Melt ◽

The Arctic Ocean ◽

The Impact

Air-sea carbon dioxide (CO2) flux is often indirectly estimated by the bulk method using the in-situ air-sea difference in CO2 fugacity and a wind speed dependent parameterisation of the gas transfer velocity (K). In the summer, sea-ice melt in the Arctic Ocean generates strong shallow stratification with significant gradients in temperature, salinity, dissolved inorganic carbon (DIC) and alkalinity (TA), and thus a near-surface CO2 fugacity &#160;(fCO2w) gradient. This gradient can cause an error in bulk air-sea CO2 flux estimates when the fCO2w is measured by the ship&#8217;s underway system at ~5 m depth. Direct air-sea CO2 flux measurement by eddy covariance (EC) is free from the impact of shallow stratification because the EC CO2 flux does not rely on a fCO2w measurement. In this study, we use summertime EC flux measurements from the Arctic Ocean to back-calculate the sea surface fCO2w and temperature and compare them with the underway measurements. We show that the EC air-sea CO2 flux agrees well with the bulk flux in areas less likely to be influenced by ice melt (salinity > 32). However, in regions with salinity less than 32, the underway fCO2w is higher than the EC estimate of surface fCO2w and thus the bulk estimate of ocean CO2 uptake is underestimated. The fCO2w difference can be partly explained by the surface to sub-surface temperature difference. The EC estimate of surface temperature is lower than the sub-surface water temperature and this difference is wind speed-dependent. Upper-ocean salinity gradients from CTD profiles suggest likely difference in DIC and TA concentrations between the surface and sub-surface water. These DIC and TA gradients likely explain much of the near-surface fCO2w gradient. Accelerating summertime loss of sea ice results in additional meltwater, which enhances near-surface stratification and increases the uncertainty of bulk air-sea CO2 flux estimates in polar regions.

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Slope hydrology and permafrost: The effect of snowmelt N transport on downslope ecosystem

10.5194/egusphere-egu2020-2927 ◽

2020 ◽

Author(s):

Laura Helene Rasmussen ◽

Per Ambus ◽

Wenxin Zhang ◽

Per Erik Jansson ◽

Anders Michelsen ◽

...

Keyword(s):

Surface Water ◽

Active Layer ◽

Water Movement ◽

Ecosystem Respiration ◽

N Uptake ◽

Growing Season ◽

Potential Effect ◽

Near Surface ◽

Vegetation Growth ◽

N Input

In the permafrost-affected landscape, surface and near-surface water movement links areas of higher elevation with lowlands and surface water bodies. Water supply is dominated by snow melt and is thus highly seasonal, as most water moves on the frozen surface in spring, passing only a thin layer of thawed soil. Soluble nutrients mobilized by soil thaw may thus be transported laterally from upslope to downslope ecosystems, which in nutrient-limited cold ecosystems may affect vegetation, ecosystem respiration and surface-atmosphere interaction. In a nitrogen (N) limited ecosystem, however, released inorganic N may in reality not travel far downslope. This study quantifies the potential effect of the snowmelt water nutrient transport by tracing dissolved N in meltwater moving downslope on the frozen surface in a W Greenlandic slope with a snow fan supplying meltwater throughout most of the summer. We use the stable isotopes 15N and D applied simultaneously on top of the frozen surface upslope in a combined solution to investigate the behavior of water and dissolved N flow patterns. We further address the effect of season by tracing N supplied in the early thaw season (30 cm to the frozen surface) and in the late thaw season (90 cm to the frozen surface). Monitoring the slope in detail, we then use the numerical coupled heat-and-mass transfer Coup model to simulate the biotics and abiotics of the receiving ecosystem and study the importance of the lateral N input and the effect of increased N transport in a warmer future. &#160; About 50 % of the N tracer was retained in the ecosystem immediately below injection in the early growing season (30 cm active layer), whereas about 35 % was retained in the later growing season (90 cm active layer). Most of the applied 15N was rapidly immobilized by microbes and into the bulk soil, whereas only a few percentages was taken up by the vegetation. D recovery seemed to follow the pattern of microbial N uptake, suggesting that N and D moved physically from the frozen surface and to the immediate subsoil together.Modelling the ecosystem based on measured N and C pool sizes, meteorology, soil temperature and &#8211;moisture revealed a large N constrain on vegetation growth. The current observed vegetation could not be explained with the measured pools alone, suggesting an &#8220;invisible&#8221; source of N to support the observed vegetation. We conclude that a substantial fraction of lateral N input is transported further downslope, but that increases in N release and transport might not affect vegetation immediately, as most supplied N ends in the soil pool. Vegetation in the receiving ecosystem relies on an external N source, which could be dissolved N transported by snowmelt water on the frozen surface. Snowmelt redistribution of N in the landscape may thus be a factor to account for when studying N cycling in a spatial context.

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Microplastics distribution in the Eurasian Arctic is affected by Atlantic waters and Siberian rivers

Communications Earth & Environment ◽

10.1038/s43247-021-00091-0 ◽

2021 ◽

Vol 2 (1) ◽

Cited By ~ 1

Author(s):

Evgeniy Yakushev ◽

Anna Gebruk ◽

Alexander Osadchiev ◽

Svetlana Pakhomova ◽

Amy Lusher ◽

...

Keyword(s):

Surface Water ◽

Surface Waters ◽

Water Masses ◽

The Arctic ◽

Plastic Pollution ◽

Siberian River ◽

Highest Weight ◽

Surface Samples ◽

Atlantic Origin ◽

Type Size

AbstractPlastic pollution is globally recognised as a threat to marine ecosystems, habitats, and wildlife, and it has now reached remote locations such as the Arctic Ocean. Nevertheless, the distribution of microplastics in the Eurasian Arctic is particularly underreported. Here we present analyses of 60 subsurface pump water samples and 48 surface neuston net samples from the Eurasian Arctic with the goal to quantify and classify microplastics in relation to oceanographic conditions. In our study area, we found on average 0.004 items of microplastics per m3 in the surface samples, and 0.8 items per m3 in the subsurface samples. Microplastic characteristics differ significantly between Atlantic surface water, Polar surface water and discharge plumes of the Great Siberian Rivers, allowing identification of two sources of microplastic pollution (p < 0.05 for surface area, morphology, and polymer types). The highest weight concentration of microplastics was observed within surface waters of Atlantic origin. Siberian river discharge was identified as the second largest source. We conclude that these water masses govern the distribution of microplastics in the Eurasian Arctic. The microplastics properties (i.e. abundance, polymer type, size, weight concentrations) can be used for identification of the water masses.

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An evaluation of water quality at Sandhill Wetland: implications for reclaiming wetlands above soft tailings deposits in northern Alberta, Canada

Wetlands Ecology and Management ◽

10.1007/s11273-020-09771-8 ◽

2021 ◽

Author(s):

Jeremy A. Hartsock ◽

Jessica Piercey ◽

Melissa K. House ◽

Dale H. Vitt

Keyword(s):

Water Quality ◽

Electrical Conductivity ◽

Surface Water ◽

Water Chemistry ◽

Water Quality Monitoring ◽

Total Alkalinity ◽

Near Surface ◽

Water Quality Guidelines ◽

Quality Guidelines ◽

Annual Water

AbstractThe experimental Sandhill Wetland is the first permanent reclamation of a composite tailings deposit, and annual water quality monitoring is of specific interest for evaluating and predicting long-term reclamation performance. Here, we present water chemistry monitoring data obtained from Sandhill Wetland (years 2009–2019) and compare results to twelve natural reference wetlands and to environmental quality guidelines for Alberta surface waters. By comparing water quality at Sandhill Wetland and natural sites to established guidelines, we can begin to document the natural background water quality of wetlands in the region and examine if guideline exceedances are seen in natural undisturbed environments, or appear only at active reclamation sites. At Sandhill Wetland the dominant ions in near-surface water were bicarbonate, sulfate, chloride, sodium, calcium, and magnesium. Since the first growing season concentrations for these ions have increased annually, causing concurrent increases in electrical conductivity. In year 2019, water chemistry at Sandhill Wetland was most comparable to regional saline fens, systems that exhibit elevated electrical conductivity and high sodicity. Near-surface water at Sandhill Wetland exceeded water quality guidelines for three substances/properties (dissolved chloride, iron, and total alkalinity) in the most recent year of monitoring. The saline fen natural sites also exceeded water quality guidelines for the same chemical substances/properties, suggesting guideline exceedances are a norm for some natural wetland site types in the region. Of note, in each year of monitoring at Sandhill Wetland, dissolved organic compounds evaluated in sub- and near-surface water were below detection limits.

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A warm jet in a cold ocean

Nature Communications ◽

10.1038/s41467-021-22505-5 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Jennifer A. MacKinnon ◽

Harper L. Simmons ◽

John Hargrove ◽

Jim Thomson ◽

Thomas Peacock ◽

...

Keyword(s):

The Arctic ◽

Bering Strait ◽

Near Surface ◽

Ice Melt ◽

Beaufort Gyre ◽

The Pacific ◽

Climate Simulations ◽

Initial Evolution ◽

Forecast Models

AbstractUnprecedented quantities of heat are entering the Pacific sector of the Arctic Ocean through Bering Strait, particularly during summer months. Though some heat is lost to the atmosphere during autumn cooling, a significant fraction of the incoming warm, salty water subducts (dives beneath) below a cooler fresher layer of near-surface water, subsequently extending hundreds of kilometers into the Beaufort Gyre. Upward turbulent mixing of these sub-surface pockets of heat is likely accelerating sea ice melt in the region. This Pacific-origin water brings both heat and unique biogeochemical properties, contributing to a changing Arctic ecosystem. However, our ability to understand or forecast the role of this incoming water mass has been hampered by lack of understanding of the physical processes controlling subduction and evolution of this this warm water. Crucially, the processes seen here occur at small horizontal scales not resolved by regional forecast models or climate simulations; new parameterizations must be developed that accurately represent the physics. Here we present novel high resolution observations showing the detailed process of subduction and initial evolution of warm Pacific-origin water in the southern Beaufort Gyre.

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