scholarly journals Extremely wet summer events enhance permafrost thaw for multiple years in Siberian tundra

2021 ◽  
Author(s):  
Rúna Magnússon ◽  
Alexandra Hamm ◽  
Sergey V. Karsanaev ◽  
Juul Limpens ◽  
David Kleijn ◽  
...  
Keyword(s):  
Summer Precipitation ◽  
Frozen Soil ◽  
The Arctic ◽  
Permafrost Thaw ◽  
Air Temperatures ◽  
Thaw Depth ◽  
Controlled Irrigation ◽  
Carry Over ◽  
Thaw Period ◽  
Carry Over Effect

Abstract Permafrost thaw can accelerate climate warming by releasing carbon from previously frozen soil in the form of greenhouse gases. Summer precipitation extremes have been proposed to increase permafrost thaw, but the magnitude and duration of this effect are poorly understood. Here we present empirical evidence showing that one extremely wet summer (+100mm; 120% increase relative to average summer precipitation) enhances thaw depth by up to 35% and prolonged the thaw period in a controlled irrigation experiment in an ice-rich Siberian tundra site. The effect persisted over two subsequent summers, demonstrating a carry-over effect of extremely wet summers. Using soil thermal hydrological modelling, we show that precipitation-induced increases in thaw are most pronounced during warm summers with mid-summer precipitation peaks. Our results suggest that, with summer precipitation and temperature both increasing in the Arctic, permafrost will likely degrade and disappear faster than is currently anticipated based on rising air temperatures alone.

scholarly journals Post-fire vegetation succession in the Siberian subarctic tundra over 45 years

2019 ◽  
Author(s):  
Ramona J. Heim ◽  
Anna Bucharova ◽  
Leya Brodt ◽  
Johannes Kamp ◽  
Daniel Rieker ◽  
...  
Keyword(s):  
Soil Temperature ◽  
Vegetation Cover ◽  
The Arctic ◽  
Vegetation Recovery ◽  
Long Term Effects ◽  
Forest Tundra ◽  
Permafrost Thaw ◽  
Legacy Effect ◽  
Thaw Depth

AbstractWildfires are relatively rare in subarctic tundra ecosystems, but they can strongly change ecosystem properties. Short-term fire effects on subarctic tundra vegetation are well documented, but long-term vegetation recovery has been studied less. The frequency of tundra fires will increase with climate warming. Understanding the long-term effects of fire is necessary to predict future ecosystem changes.We used a space-for-time approach to assess vegetation recovery after fire over more than four decades. We studied soil and vegetation patterns on three large fire scars (>44, 28 and 12 years old) in dry, lichen-dominated forest tundra in Western Siberia. On 60 plots, we determined soil temperature and permafrost thaw depth, sampled vegetation and measured plant functional traits. We assessed trends in NDVI to support the field-based results on vegetation recovery.Soil temperature, permafrost thaw depth and total vegetation cover had recovered to pre-fire levels after >44 years, as well as total vegetation cover. In contrast, after >44 years, functional groups had not recovered to the pre-fire state. Burnt areas had lower lichen and higher bryophyte and shrub cover. The dominating shrub species, Betula nana, exhibited a higher vitality (higher specific leaf area and plant height) on burnt compared with control plots, suggesting a fire legacy effect in shrub growth. Our results confirm patterns of shrub encroachment after fire that were detected before in other parts of the Arctic and Subarctic. In the so far poorly studied Western Siberian forest tundra we demonstrate for the first time, long-term fire-legacies on the functional composition of relatively dry shrub- and lichen-dominated vegetation.

scholarly journals Performance of Highway Embankments in the Arctic Corridor Constructed under Winter Conditions

2020 ◽  
Author(s):  
Earl Marvin De Guzman ◽  
Marolo Alfaro ◽  
Guy Doré ◽  
Lukas U. Arenson ◽  
Aron Piamsalee
Keyword(s):  
Performance Test ◽  
Frozen Soil ◽  
The Arctic ◽  
Side Slope ◽  
Displacement Sensors ◽  
Fill Material ◽  
Analysis And Synthesis ◽  
Thaw Depth ◽  
Ice Content ◽  
Bottom Portion

There are uncertainties related to the mechanical behaviour of embankments where frozen soil is used as fill material and experience natural thawing and settlements during the first thawing season following construction. Fill material of embankments in the Arctic are primarily sourced from locally-available borrow sites which, in certain areas, are predominantly composed of fine till with high ground ice content. Side slope sloughing and fill cracking typically occur due to thawing of the frozen soil and development of localized thaw settlements under the embankment shoulders and side slopes. To assess a frozen fill embankment performance, test sections were constructed along the Inuvik-Tuktoyaktuk Highway in the Northwest Territories, Canada and instrumented with temperature and displacement sensors. One test section was reinforced with layers of wicking woven geotextiles at its side slopes to primarily provide reinforcement against lateral movements and drainage during the thawing season. Field data show that the central and bottom portion of the embankment fill is still frozen while the thaw depth has increased at the toe. This paper presents the analysis and synthesis of the first three-year monitored performance of the embankment test sections following construction.

scholarly journals Increased rainfall stimulates permafrost thaw across a variety of Interior Alaskan boreal ecosystems

2021 ◽  
Author(s):  
Thomas Douglas ◽  
Merritt Turetsky ◽  
Charles Koven
Keyword(s):  
Mixed Forest ◽  
Summer Precipitation ◽  
Arctic Region ◽  
Heat Fluxes ◽  
The Arctic ◽  
Order Estimate ◽  
Conifer Forest ◽  
Permafrost Thaw ◽  
Tussock Tundra

Earth’s high latitudes are projected to experience warmer and wetter summers in the future but ramifications for soil thermal processes and permafrost thaw are poorly understood. Here we present 2750 end of summer thaw depths representing a range of vegetation characteristics in Interior Alaska measured over a 5-year period. This included the top and third wettest summers in the 91-year record and three summers with precipitation close to mean historical values. Increased rainfall led to deeper thaw across all sites with an increase of 0.7 ± 0.1 cm of thaw per cm of additional rain. Disturbed and wetland sites were the most vulnerable to rain-induced thaw with ~1 cm of surface thaw per additional 1 cm of rain. Permafrost in tussock tundra, mixed forest, and conifer forest was less sensitive to rain-induced thaw. A simple energy budget model yields seasonal thaw values smaller than the linear regression of our measurements but provides a first-order estimate of the role of rain-driven sensible heat fluxes in high-latitude terrestrial permafrost. This study demonstrates substantial permafrost thaw from the projected increasing summer precipitation across most of the Arctic region.

scholarly journals Standardized monitoring of permafrost thaw: a user-friendly, multi-parameter protocol

2021 ◽  
Author(s):  
Julia Boike ◽  
Sarah Chadburn ◽  
Julia Martin ◽  
Simon Zwieback ◽  
Inge H.J. Althuizen ◽  
...  
Keyword(s):  
Land Surface ◽  
Ground Surface ◽  
Surface Characteristics ◽  
The Arctic ◽  
Vegetation Height ◽  
Permafrost Thaw ◽  
Standardized Protocol ◽  
Indigenous Groups ◽  
Thaw Depth ◽  
User Friendly

Climate change is destabilizing permafrost landscapes, affecting infrastructure, ecosystems and human livelihoods. The rate of permafrost thaw is controlled by surface and subsurface properties and processes, all of which are potentially linked with each other. Yet, no standardized protocol exists for measuring permafrost thaw and related processes and properties in a linked manner. The permafrost thaw action group of the Terrestrial Multidisciplinary distributed Observatories for the Study of the Arctic Connections (T-MOSAiC) project has developed a protocol, for use by non-specialist scientists and technicians, citizen scientists and indigenous groups, to collect standardized metadata and data on permafrost thaw. The protocol introduced here addresses the need to jointly measure permafrost thaw and the associated surface and subsurface environmental conditions. The parameters measured along transects are: snow depth, thaw depth, vegetation height, soil texture, and water level. The metadata collection includes data on timing of data collection, geographical coordinates, land surface characteristics (vegetation, ground surface, water conditions), as well as photographs. Our hope is that this openly available dataset will also be highly valuable for validation and parameterization of numerical and conceptual models, thus to the broad community represented by the T-MOSAIC project.

scholarly journals Increased rainfall stimulates permafrost thaw across a variety of Interior Alaskan boreal ecosystems

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Thomas A. Douglas ◽  
Merritt R. Turetsky ◽  
Charles D. Koven
Keyword(s):  
Mixed Forest ◽  
Summer Precipitation ◽  
Arctic Region ◽  
Heat Fluxes ◽  
The Arctic ◽  
Order Estimate ◽  
Conifer Forest ◽  
Permafrost Thaw ◽  
Tussock Tundra

AbstractEarth’s high latitudes are projected to experience warmer and wetter summers in the future but ramifications for soil thermal processes and permafrost thaw are poorly understood. Here we present 2750 end of summer thaw depths representing a range of vegetation characteristics in Interior Alaska measured over a 5 year period. This included the top and third wettest summers in the 91-year record and three summers with precipitation close to mean historical values. Increased rainfall led to deeper thaw across all sites with an increase of 0.7 ± 0.1 cm of thaw per cm of additional rain. Disturbed and wetland sites were the most vulnerable to rain-induced thaw with ~1 cm of surface thaw per additional 1 cm of rain. Permafrost in tussock tundra, mixed forest, and conifer forest was less sensitive to rain-induced thaw. A simple energy budget model yields seasonal thaw values smaller than the linear regression of our measurements but provides a first-order estimate of the role of rain-driven sensible heat fluxes in high-latitude terrestrial permafrost. This study demonstrates substantial permafrost thaw from the projected increasing summer precipitation across most of the Arctic region.

scholarly journals Retrieval of Summer Sea Ice Concentration in the Pacific Arctic Ocean from AMSR2 Observations and Numerical Weather Data Using Random Forest Regression

2021 ◽  
Vol 13 (12) ◽  
pp. 2283
Author(s):  
Hyangsun Han ◽  
Sungjae Lee ◽  
Hyun-Cheol Kim ◽  
Miae Kim
Keyword(s):  
Random Forest ◽  
Sea Ice ◽  
Arctic Ocean ◽  
Open Water ◽  
The Arctic ◽  
Atmospheric Effects ◽  
Sea Ice Concentration ◽  
Air Temperatures ◽  
The Pacific ◽  
Ice Concentration

The Arctic sea ice concentration (SIC) in summer is a key indicator of global climate change and important information for the development of a more economically valuable Northern Sea Route. Passive microwave (PM) sensors have provided information on the SIC since the 1970s by observing the brightness temperature (TB) of sea ice and open water. However, the SIC in the Arctic estimated by operational algorithms for PM observations is very inaccurate in summer because the TB values of sea ice and open water become similar due to atmospheric effects. In this study, we developed a summer SIC retrieval model for the Pacific Arctic Ocean using Advanced Microwave Scanning Radiometer 2 (AMSR2) observations and European Reanalysis Agency-5 (ERA-5) reanalysis fields based on Random Forest (RF) regression. SIC values computed from the ice/water maps generated from the Korean Multi-purpose Satellite-5 synthetic aperture radar images from July to September in 2015–2017 were used as a reference dataset. A total of 24 features including the TB values of AMSR2 channels, the ratios of TB values (the polarization ratio and the spectral gradient ratio (GR)), total columnar water vapor (TCWV), wind speed, air temperature at 2 m and 925 hPa, and the 30-day average of the air temperatures from the ERA-5 were used as the input variables for the RF model. The RF model showed greatly superior performance in retrieving summer SIC values in the Pacific Arctic Ocean to the Bootstrap (BT) and Arctic Radiation and Turbulence Interaction STudy (ARTIST) Sea Ice (ASI) algorithms under various atmospheric conditions. The root mean square error (RMSE) of the RF SIC values was 7.89% compared to the reference SIC values. The BT and ASI SIC values had three times greater values of RMSE (20.19% and 21.39%, respectively) than the RF SIC values. The air temperatures at 2 m and 925 hPa and their 30-day averages, which indicate the ice surface melting conditions, as well as the GR using the vertically polarized channels at 23 GHz and 18 GHz (GR(23V18V)), TCWV, and GR(36V18V), which accounts for atmospheric water content, were identified as the variables that contributed greatly to the RF model. These important variables allowed the RF model to retrieve unbiased and accurate SIC values by taking into account the changes in TB values of sea ice and open water caused by atmospheric effects.

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.

Comparison of the Arctic upper-air temperatures from radiosonde and radio occultation observations

2018 ◽  
Vol 37 (1) ◽  
pp. 30-39
Author(s):  
Liang Chang ◽  
Lixin Guo ◽  
Guiping Feng ◽  
Xuerui Wu ◽  
Guoping Gao ◽  
...  
Keyword(s):  
Radio Occultation ◽  
The Arctic ◽  
Air Temperatures

scholarly journals Extreme Warming in the Kara Sea and Barents Sea during the Winter Period 2000–16

2017 ◽  
Vol 30 (22) ◽  
pp. 8913-8927 ◽  
Author(s):  
Svenja H. E. Kohnemann ◽  
Günther Heinemann ◽  
David H. Bromwich ◽  
Oliver Gutjahr
Keyword(s):  
Sea Ice ◽  
Air Temperature ◽  
Barents Sea ◽  
Kara Sea ◽  
The Arctic ◽  
Winter Period ◽  
Limited Area ◽  
Spatial And Temporal Variability ◽  
Large Variability ◽  
Air Temperatures

The regional climate model COSMO in Climate Limited-Area Mode (COSMO-CLM or CCLM) is used with a high resolution of 15 km for the entire Arctic for all winters 2002/03–2014/15. The simulations show a high spatial and temporal variability of the recent 2-m air temperature increase in the Arctic. The maximum warming occurs north of Novaya Zemlya in the Kara Sea and Barents Sea between March 2003 and 2012 and is responsible for up to a 20°C increase. Land-based observations confirm the increase but do not cover the maximum regions that are located over the ocean and sea ice. Also, the 30-km version of the Arctic System Reanalysis (ASR) is used to verify the CCLM for the overlapping time period 2002/03–2011/12. The differences between CCLM and ASR 2-m air temperatures vary slightly within 1°C for the ocean and sea ice area. Thus, ASR captures the extreme warming as well. The monthly 2-m air temperatures of observations and ERA-Interim data show a large variability for the winters 1979–2016. Nevertheless, the air temperature rise since the beginning of the twenty-first century is up to 8 times higher than in the decades before. The sea ice decrease is identified as the likely reason for the warming. The vertical temperature profiles show that the warming has a maximum near the surface, but a 0.5°C yr−1 increase is found up to 2 km. CCLM, ASR, and also the coarser resolved ERA-Interim data show that February and March are the months with the highest 2-m air temperature increases, averaged over the ocean and sea ice area north of 70°N; for CCLM the warming amounts to an average of almost 5°C for 2002/03–2011/12.

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