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.

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

<p>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. </p><p>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. </p><p>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.</p><p>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.</p>

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.

scholarly journals Variability in nitrogen-derived trophic levels of Arctic marine biota

Polar Biology ◽  
2020 ◽  
Author(s):  
Renske P. J. Hoondert ◽  
Nico W. van den Brink ◽  
Martine J. van den Heuvel-Greve ◽  
Ad M. J. Ragas ◽  
A. Jan Hendriks
Keyword(s):  
Stable Isotopes ◽  
Enrichment Factors ◽  
Trophic Levels ◽  
The Arctic ◽  
Marine Biota ◽  
Arctic Ecosystems ◽  
Arctic Species ◽  
Single Region ◽  
Benthic Food ◽  
Species Specific

AbstractStable isotopes are often used to provide an indication of the trophic level (TL) of species. TLs may be derived by using food-web-specific enrichment factors in combination with a representative baseline species. It is challenging to sample stable isotopes for all species, regions and seasons in Arctic ecosystems, e.g. because of practical constraints. Species-specific TLs derived from a single region may be used as a proxy for TLs for the Arctic as a whole. However, its suitability is hampered by incomplete knowledge on the variation in TLs. We quantified variation in TLs of Arctic species by collating data on stable isotopes across the Arctic, including corresponding fractionation factors and baseline species. These were used to generate TL distributions for species in both pelagic and benthic food webs for four Arctic areas, which were then used to determine intra-sample, intra-study, intra-region and inter-region variation in TLs. Considerable variation in TLs of species between areas was observed. This is likely due to differences in parameter choice in estimating TLs (e.g. choice of baseline species) and seasonal, temporal and spatial influences. TLs between regions were higher than the variance observed within regions, studies or samples. This implies that TLs derived within one region may not be suitable as a proxy for the Arctic as a whole. The TL distributions derived in this study may be useful in bioaccumulation and climate change studies, as these provide insight in the variability of trophic levels of Arctic species.

scholarly journals Societal implications of a changing Arctic Ocean

AMBIO ◽  
2021 ◽  
Author(s):  
Henry P. Huntington ◽  
Andrey Zagorsky ◽  
Bjørn P. Kaltenborn ◽  
Hyoung Chul Shin ◽  
Jackie Dawson ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Indigenous Peoples ◽  
Global Climate ◽  
Rapid Change ◽  
The Arctic ◽  
Cultural Continuity ◽  
Societal Implications ◽  
Arctic Ecosystems ◽  
The Many

AbstractThe Arctic Ocean is undergoing rapid change: sea ice is being lost, waters are warming, coastlines are eroding, species are moving into new areas, and more. This paper explores the many ways that a changing Arctic Ocean affects societies in the Arctic and around the world. In the Arctic, Indigenous Peoples are again seeing their food security threatened and cultural continuity in danger of disruption. Resource development is increasing as is interest in tourism and possibilities for trans-Arctic maritime trade, creating new opportunities and also new stresses. Beyond the Arctic, changes in sea ice affect mid-latitude weather, and Arctic economic opportunities may re-shape commodities and transportation markets. Rising interest in the Arctic is also raising geopolitical tensions about the region. What happens next depends in large part on the choices made within and beyond the Arctic concerning global climate change and industrial policies and Arctic ecosystems and cultures.

scholarly journals An Evaluation of Surface Atmospheric Changes over the Arctic Ocean for 2000–09 Using Recent Reanalyses

2015 ◽  
Vol 19 (2) ◽  
pp. 1-18 ◽  
Author(s):  
Ayan H. Chaudhuri ◽  
Rui M. Ponte
Keyword(s):  
Arctic Ocean ◽  
Extreme Event ◽  
Longwave Radiation ◽  
Remotely Sensed ◽  
Surface Radiation ◽  
Shortwave Radiation ◽  
The Arctic ◽  
Near Surface ◽  
The Arctic Ocean ◽  
Ice Retreat

Abstract The authors examine five recent reanalysis products [NCEP Climate Forecast System Reanalysis (CFSR), Modern-Era Retrospective Analysis for Research and Applications (MERRA), Japanese 25-year Reanalysis Project (JRA-25), Interim ECMWF Re-Analysis (ERA-Interim), and Arctic System Reanalysis (ASR)] for 1) trends in near-surface radiation fluxes, air temperature, and humidity, which are important indicators of changes within the Arctic Ocean and also influence sea ice and ocean conditions, and 2) fidelity of these atmospheric fields and effects for an extreme event: namely, the 2007 ice retreat. An analysis of trends over the Arctic for the past decade (2000–09) shows that reanalysis solutions have large spreads, particularly for downwelling shortwave radiation. In many cases, the differences in significant trends between the five reanalysis products are comparable to the estimated trend within a particular product. These discrepancies make it difficult to establish a consensus on likely changes occurring in the Arctic solely based on results from reanalyses fields. Regarding the 2007 ice retreat event, comparisons with remotely sensed estimates of downwelling radiation observations against these reanalysis products present an ambiguity. Remotely sensed observations from a study cited herewith suggest a large increase in downwelling summertime shortwave radiation and decrease in downwelling summertime longwave radiation from 2006 and 2007. On the contrary, the reanalysis products show only small gains in summertime shortwave radiation, if any; however, all the products show increases in downwelling longwave radiation. Thus, agreement within reanalysis fields needs to be further checked against observations to assess possible biases common to all products.

scholarly journals Observed and predicted effects of climate change on Arctic caribou and reindeer

2018 ◽  
Vol 26 (1) ◽  
pp. 13-25 ◽  
Author(s):  
Conor D. Mallory ◽  
Mark S. Boyce
Keyword(s):  
Climate Change ◽  
Rangifer Tarandus ◽  
The Arctic ◽  
Arctic Ecosystems ◽  
Global Trends ◽  
Warming Climate ◽  
The Many ◽  
Rapid Environmental Change ◽  
Full Consideration ◽  
Strong Concern

The ability of many species to adapt to the shifting environmental conditions associated with climate change will be a key determinant of their persistence in the coming decades. This is a challenge already faced by species in the Arctic, where rapid environmental change is well underway. Caribou and reindeer (Rangifer tarandus) play a key role in Arctic ecosystems and provide irreplaceable socioeconomic value to many northern peoples. Recent decades have seen declines in many Rangifer populations, and there is strong concern that climate change is threatening the viability of this iconic Arctic species. We examine the literature to provide a thorough and full consideration of the many environmental factors that limit caribou and reindeer populations, and how these might be affected by a warming climate. Our review suggests that the response of Rangifer populations to climate change is, and will continue to be, varied in large part to their broad circumpolar distribution. While caribou and reindeer could have some resilience to climate change, current global trends in abundance undermine all but the most precautionary outlooks. Ultimately, the conservation of Rangifer populations will require careful management that considers the local and regional manifestations of climate change.

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