The Origin of Massive Icy Beds in Permafrost, Western Arctic Coast, Canada

1971 ◽  
Vol 8 (4) ◽  
pp. 397-422 ◽  
Author(s):  
J. Ross Mackay
Keyword(s):  
The Arctic ◽  
Ground Ice ◽  
Widespread Occurrence ◽  
Sea Floor ◽  
Western Arctic ◽  
Arctic Coast ◽  
Ice Content ◽  
Glacier Advance ◽  
Drill Holes ◽  
Level Lowering

Massive beds of ground ice are shown to exist along the arctic coastal plain east of the Alaska–Yukon boundary for a distance of at least 500 km. The massive ground ice can be seen in both undisturbed and glacially disturbed Pleistocene sediments. An examination of several thousand seismic shot hole logs, from drill holes of 15 to 35 m in depth, also corroborates the widespread occurrence of ground ice. The icy beds typically have an ice content, defined in terms of the weight of ice to dry soil, in excess of 200% for sections as much as 35 m thick. A theory is presented which suggests that: the ice is of segregation origin; the source of excess water was from the expulsion of ground water during the freezing of sands; and high pore water pressures, favorable to ice segregation, developed beneath an aggrading impermeable permafrost cover. Permafrost aggradation may have occurred either on an exposed sea floor during a period of sea level lowering which would have accompanied a glacier advance, or following a warm interval in which there had been deep thaw. Similarities in the origin of pingo ice and massive ice are discussed.

Physical and temporal factors controlling the development of near-surface ground ice at Illisarvik, western Arctic coast, Canada

2012 ◽  
Vol 49 (9) ◽  
pp. 1096-1110 ◽  
Author(s):  
H. Brendan O’Neill ◽  
C.R. Burn
Keyword(s):  
Important Variable ◽  
Lake Basin ◽  
Ground Ice ◽  
Near Surface ◽  
Marginal Areas ◽  
Permafrost Table ◽  
Western Arctic ◽  
Arctic Coast ◽  
Ice Content ◽  
Secondary Variable

Near-surface permafrost was sampled in summer 2010 at 26 sites in the Illisarvik drained-lake basin and nine sites in the surrounding tundra on Richards Island, NWT, to investigate the growth of segregated near-surface ground ice. Permafrost and ground ice have developed in the lake basin since drainage in 1978. The lake bed soils are predominantly silts of varying moisture and organic-matter contents, with sandier soils near the lake margins. Excess-ice contents in the basin were also variable, and ice enrichment was observed to a maximum depth of 60 cm below the 2010 permafrost table. Shrub-covered, wet areas had the highest mean excess-ice content in the top 50 cm of permafrost (10%), while grassy, dryer areas (4%) and poorly vegetated marginal areas (<1%) were less enriched with ice. Site wetness was the most important variable associated with near-surface excess-ice content in the lake basin. Silt content was a secondary variable. Mean excess-ice content in the top 50 cm of permafrost at tundra sites (25%) was much greater than in the basin, with ice enrichment to greater depths, likely a result of the time available for permafrost aggradation since the early Holocene climatic optimum.

Glacial Boulders on the Arctic Coast of Alaska

ARCTIC ◽  
1958 ◽  
Vol 11 (2) ◽  
pp. 70 ◽  
Author(s):  
Gerald R. McCarthy
Keyword(s):  
Rock Type ◽  
The Arctic ◽  
Petrographic Analysis ◽  
Brooks Range ◽  
Sea Floor ◽  
Arctic Coast ◽  
Made In

Reports incidental observations made in the Barrow-Cape Simpson area 1949-50. Pleistocene glaciers of Alaska did not extend north beyond the northern foothills of the Brooks Range, yet glacial boulders have been reported near and along the coast. Altogether 56 such erratic boulders from sheltered spots on the shore, as far as 8-9 mi inland on the tundra and a few from the present sea floor were examined. Their location and size, rock type with field description and petrographic analysis are tabulated. Of granite (16), diabase (17), quartzite (10), etc., they range in weight from 2-3 lbs. to 4-5 tons. They are thought to represent morainic material left by melting icebergs, and the bergs to have been produced from glaciers in widely separated areas.

Surficial materials and related ground ice conditions, Slave Province, N.W.T., Canada

1999 ◽  
Vol 36 (7) ◽  
pp. 1227-1238 ◽  
Author(s):  
Lynda A Dredge ◽  
Daniel E Kerr ◽  
Stephen A Wolfe
Keyword(s):  
Gulf Coast ◽  
Regional Scale ◽  
Coarse Grained ◽  
Silty Clay ◽  
Ground Ice ◽  
Wide Range ◽  
Ice Conditions ◽  
Western Arctic ◽  
Climatic History ◽  
Ice Content

Surficial mapping and geologic information on the nature and evolution of surficial materials in the Slave geologic province indicate that the geotechnical properties and potential ground ice contents associated with these materials depend largely upon their provenance, depositional conditions, and the postglacial climatic history. This information may be used to provide a regional-scale view of the distribution of ground ice conditions and terrain sensitivities associated with various surficial materials. In till veneers and blankets, ground ice content is generally low, as suggested by lack of thermokarst and other permafrost features. However, distinctive surface relief in hummocky till including kettle depressions, rim-ridges, and shallow thaw flowslides may be attributed to massive ice, resulting in sensitive till terrain. Although many outwash sediments have low ice contents near the surface, massive ice ranging from 5 to 10 m thick is present in some eskers and ice-contact outwash sediments. These are associated with thermokarst, slope movement, and collapse features, indicative of meltout or creep of large bodies of massive ice. The terrain sensitivity associated with these deposits is typically low to moderate, due to the coarse-grained nature of the sediments. In contrast, terrain sensitivity is high, and active-layer detachment slides are common along the Coronation Gulf coast where frozen silty clay marine sediments contain a wide range of ice contents. Results from this study may be applied to a much more extensive area of the glaciated western Arctic mainland and adjacent Arctic coastal plain in which materials with a similar glacial history are found.

scholarly journals Top-of-permafrost ground ice indicated by remotely sensed late-season subsidence

2021 ◽  
Vol 15 (4) ◽  
pp. 2041-2055
Author(s):  
Simon Zwieback ◽  
Franz J. Meyer
Keyword(s):  
High Sensitivity ◽  
Remotely Sensed ◽  
The Arctic ◽  
Arctic Ecosystems ◽  
Ground Ice ◽  
Automated Mapping ◽  
Late Season ◽  
Warm Summer ◽  
Permafrost Ground ◽  
Ice Content

Abstract. Ground ice is foundational to the integrity of Arctic ecosystems and infrastructure. However, we lack fine-scale ground ice maps across almost the entire Arctic, chiefly because there is no established method for mapping ice-rich permafrost from space. Here, we assess whether remotely sensed late-season subsidence can be used to identify ice-rich permafrost. The idea is that, towards the end of an exceptionally warm summer, the thaw front can penetrate materials that were previously perennially frozen, triggering increased subsidence if they are ice rich. Focusing on northwestern Alaska, we test the idea by comparing the Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR) late-season subsidence observations to permafrost cores and an independently derived ground ice classification. We find that the late-season subsidence in an exceptionally warm summer was 4–8 cm (5th–95th percentiles) in the ice-rich areas, while it was low in ice-poor areas (−1 to 2 cm; 5th–95th percentiles). The distributions of the late-season subsidence overlapped by 2 %, demonstrating high sensitivity and specificity for identifying top-of-permafrost excess ground ice. The strengths of late-season subsidence include the ease of automation and its applicability to areas that lack conspicuous manifestations of ground ice, as often occurs on hillslopes. One limitation is that it is not sensitive to excess ground ice below the thaw front and thus the total ice content. Late-season subsidence can enhance the automated mapping of permafrost ground ice, complementing existing (predominantly non-automated) approaches based on largely indirect associations with vegetation and periglacial landforms. Thanks to its suitability for mapping ice-rich permafrost, satellite-observed late-season subsidence can make a vital contribution to anticipating terrain instability in the Arctic and sustainably stewarding its ecosystems.

scholarly journals Vulnerable top-of-permafrost ground ice indicated by remotely sensed late-season subsidence

2020 ◽  
Author(s):  
Simon Zwieback ◽  
Franz J. Meyer
Keyword(s):  
High Sensitivity ◽  
Satellite Observations ◽  
The Arctic ◽  
Arctic Ecosystems ◽  
Ground Ice ◽  
Automated Mapping ◽  
Late Season ◽  
Warm Summer ◽  
Permafrost Ground ◽  
Ice Content

Abstract. Ground ice is foundational to the integrity of Arctic ecosystems and infrastructure. However, we lack fine-scale ground ice maps across almost the entire Arctic, chiefly because ground ice cannot be observed directly from space. Focusing on northwestern Alaska, we assess the suitability of late-season subsidence from Sentinel-1 satellite observations as a direct indicator of vulnerable excess ground ice at the top of permafrost. The idea is that, towards the end of an exceptionally warm summer, the thaw front can penetrate materials that were previously perennially frozen, triggering increased subsidence if they are ice rich. For locations independently determined to be ice rich, the late-season subsidence in an exceptionally warm summer was 4–8 cm (5th–95th percentile), while it was lower for ice-poor areas (−1–2 cm). The distributions overlapped by 2 %, demonstrating high sensitivity and specificity for identifying top-of-permafrost excess ground ice. The strengths of late-season subsidence include the ease of automation and its applicability to areas that lack conspicuous manifestations of ground ice, as often occurs on hillslopes. One limitation is that it is not sensitive to excess ground ice below the thaw front and thus the total ice content. Late-season subsidence can enhance the automated mapping of vulnerable permafrost ground ice, complementing existing (predominantly non-automated) approaches based on largely indirect associations with vegetation cover and periglacial landforms. Improved ground ice maps will prove indispensable for anticipating terrain instability in the Arctic and sustainably stewarding its ecosystems.

Massive ice of the Tuktoyaktuk area, western Arctic coast, Canada

1992 ◽  
Vol 29 (6) ◽  
pp. 1235-1249 ◽  
Author(s):  
J. Ross Mackay ◽  
Scott R. Dallimore
Keyword(s):  
Northwest Territories ◽  
Water Pressure ◽  
Water Source ◽  
High Water ◽  
Radiocarbon Dates ◽  
Frozen Sand ◽  
Western Arctic ◽  
Arctic Coast ◽  
Drill Holes ◽  
High Water Pressure

The extensive coastal exposure of massive underground ice at Peninsula Point, southwest of Tuktoyaktuk, Northwest Territories, is believed to be intrasedimental ice. The ice grew beneath a frozen diamicton during the downward aggradation of permafrost. The water source was probably glacier meltwater, with low negative δ18O values, that flowed, under a substantial pressure, through permeable unfrozen sands. Evidence for a high water pressure is shown by ice dikes, which extend upward from the massive ice into the superincumbent diamicton. The diamicton was frozen when the dike water was injected, as proven by the chill contacts and petrofabrics. The diamicton – massive ice contact is a conformable contact with features characteristic of downward freezing. The continuity of δ18O and δD profiles from the top of the massive ice downward to a depth of 10 m into the underlying frozen sand demonstrates a common water source for the massive ice and interstitial ice in the underlying sand. A similar continuity of δ18O profiles has been determined from three drill holes at another site 15 km northeast of Tuktoyaktuk, Northwest Territories. The ages of both the diamicton and massive ice at the Peninsula Point site are uncertain, because of unexplained differences in published radiocarbon dates.

Identifying ice-rich permafrost using remotely sensed late-season subsidence

2021 ◽  
Author(s):  
Simon Zwieback ◽  
Franz Meyer
Keyword(s):  
Critical Role ◽  
High Sensitivity ◽  
The Arctic ◽  
Ground Ice ◽  
Automated Mapping ◽  
Late Season ◽  
Warm Summer ◽  
Physically Based ◽  
Ice Wedge ◽  
Ice Content

&lt;p&gt;Despite the critical role of ground ice for permafrost ecosystems and terrain stability, we lack fine-scale ground ice maps across almost the entire Arctic. This is chiefly because ground ice cannot be observed directly from space. Here, we analyse late-season subsidence from Sentinel-1 InSAR satellite observations as a physically based indicator of vulnerable excess ground ice at the top of permafrost. The key idea is that the thaw front can penetrate materials that were previously perennially frozen at the end of a warm summer, triggering subsidence where the permafrost is ice rich. We assess the idea by comparing the InSAR observations to permafrost cores and an independently derived ground ice classification.&amp;#160;&lt;/p&gt;&lt;p&gt;We find that the late-season subsidence in an exceptionally warm summer was 4 - 8 cm (5th - 95th percentile) in the ice-rich areas, while it was lower in ice-poor areas (-1 - 2 cm). The observed distributions for ice-rich and ice-poor terrain overlapped by only 2%, demonstrating high sensitivity and specificity for identifying top-of-permafrost excess ground ice.&amp;#160;&lt;/p&gt;&lt;p&gt;The strengths of late-season subsidence include the ease of automation and its applicability to areas that lack conspicuous manifestations of ground ice, as often occurs on hillslopes. The biggest limitation is that it is not sensitive to excess ground ice below the thaw front and thus the total ice content. A further challenge is the sub-resolution variability in ground ice, ice-wedge polygons being a striking example, which needs to be accounted for when interpreting and validating the results.&lt;/p&gt;&lt;p&gt;We expect late-season subsidence to enhance the automated mapping of ice-rich permafrost terrain, complementing existing (predominantly non-automated) approaches based on largely indirect associations of ice content with vegetation and periglacial landforms. The suitability of satellite-observed late-season subsidence for mapping ice-rich permafrost can contribute to anticipating terrain instability in the Arctic and sustainably stewarding its ecosystems.&lt;/p&gt;

scholarly journals N2O dynamics in the western Arctic Ocean during the summer of 2017

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jang-Mu Heo ◽  
Seong-Su Kim ◽  
Sung-Ho Kang ◽  
Eun Jin Yang ◽  
Ki-Tae Park ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Environmental Changes ◽  
Chukchi Sea ◽  
Hot Spot ◽  
Open Water ◽  
Northern Region ◽  
The Arctic ◽  
Western Arctic Ocean ◽  
Deep Layers ◽  
Western Arctic

AbstractThe western Arctic Ocean (WAO) has experienced increased heat transport into the region, sea-ice reduction, and changes to the WAO nitrous oxide (N2O) cycles from greenhouse gases. We investigated WAO N2O dynamics through an intensive and precise N2O survey during the open-water season of summer 2017. The effects of physical processes (i.e., solubility and advection) were dominant in both the surface (0–50 m) and deep layers (200–2200 m) of the northern Chukchi Sea with an under-saturation of N2O. By contrast, both the surface layer (0–50 m) of the southern Chukchi Sea and the intermediate (50–200 m) layer of the northern Chukchi Sea were significantly influenced by biogeochemically derived N2O production (i.e., through nitrification), with N2O over-saturation. During summer 2017, the southern region acted as a source of atmospheric N2O (mean: + 2.3 ± 2.7 μmol N2O m−2 day−1), whereas the northern region acted as a sink (mean − 1.3 ± 1.5 μmol N2O m−2 day−1). If Arctic environmental changes continue to accelerate and consequently drive the productivity of the Arctic Ocean, the WAO may become a N2O “hot spot”, and therefore, a key region requiring continued observations to both understand N2O dynamics and possibly predict their future changes.

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