Active layer freeze-thaw and water storage dynamics in permafrost environments inferred from InSAR

Abstract. Freezing and thawing action of the active layer plays a significant role in soil respiration (Rs) in permafrost regions. However, little is known about how the freeze-thaw process regulates the Rs dynamics in different stages for the alpine meadow underlain by permafrost on the Qinghai-Tibet Plateau (QTP). We conducted continuous in-situ measurements of Rs and freeze-thaw process of the active layer at an alpine meadow site in the Beiluhe permafrost region of QTP to determine the regulatory mechanisms of the different freeze-thaw stages of the active layer on the Rs. We found that the freezing and thawing process of active layer modified the Rs dynamics differently in different freeze-thaw stages. The mean Rs ranged from 0.56 to 1.75 μmol/m2s across the stages, with the lowest value in the SW stage and highest value in the ST stage; and Q10 among the different freeze-thaw stages changed greatly, with maximum (4.9) in the WC stage and minimum (1.7) in the SW stage. Patterns of Rs among the ST, AF, WC, and SW stages differed, and the corresponding contribution percentages of cumulative Rs to annual total Rs were 61.54, 8.89, 18.35, and 11.2 %, respectively. Soil temperature (Ts) was the most important driver of Rs regardless of soil water status in all stages. Our results suggest that as the climate warming and permafrost degradation continue, great changes in freeze-thaw process patterns may trigger more Rs emissions from this ecosystem because of prolonged ST stage.

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Sentinel-1 InSAR Measurements of Elevation Changes over Yedoma Uplands on Sobo-Sise Island, Lena Delta

Remote Sensing ◽

10.3390/rs10071152 ◽

2018 ◽

Vol 10 (7) ◽

pp. 1152 ◽

Cited By ~ 11

Author(s):

Jie Chen ◽

Frank Günther ◽

Guido Grosse ◽

Lin Liu ◽

Hui Lin

Keyword(s):

Active Layer ◽

Late Pleistocene ◽

Air Temperature ◽

Climate Warming ◽

Temperature Fluctuations ◽

Surface Elevation ◽

Freeze Thaw ◽

Elevation Changes ◽

Mean Annual Air Temperature ◽

Lena Delta

Yedoma—extremely ice-rich permafrost with massive ice wedges formed during the Late Pleistocene—is vulnerable to thawing and degradation under climate warming. Thawing of ice-rich Yedoma results in lowering of surface elevations. Quantitative knowledge about surface elevation changes helps us to understand the freeze-thaw processes of the active layer and the potential degradation of Yedoma deposits. In this study, we use C-band Sentinel-1 InSAR measurements to map the elevation changes over ice-rich Yedoma uplands on Sobo-Sise Island, Lena Delta with frequent revisit observations (as short as six or 12 days). We observe significant seasonal thaw subsidence during summer months and heterogeneous inter-annual elevation changes from 2016–17. We also observe interesting patterns of stronger seasonal thaw subsidence on elevated flat Yedoma uplands by comparing to the surrounding Yedoma slopes. Inter-annual analyses from 2016–17 suggest that our observed positive surface elevation changes are likely caused by the delayed progression of the thaw season in 2017, associated with mean annual air temperature fluctuations.

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Soil respiration of alpine meadow is controlled by freeze–thaw processes of active layer in the permafrost region of the Qinghai–Tibet Plateau

The Cryosphere ◽

10.5194/tc-14-2835-2020 ◽

2020 ◽

Vol 14 (9) ◽

pp. 2835-2848

Author(s):

Junfeng Wang ◽

Qingbai Wu ◽

Ziqiang Yuan ◽

Hojeong Kang

Keyword(s):

Soil Respiration ◽

Active Layer ◽

Alpine Meadow ◽

Tibet Plateau ◽

Permafrost Region ◽

Permafrost Degradation ◽

Freeze Thaw ◽

Thaw Cycle ◽

Freeze Thaw Cycle ◽

Qinghai Tibet Plateau

Abstract. Freezing and thawing action of the active layer plays a significant role in soil respiration (Rs) in permafrost regions. However, little is known about how the freeze–thaw processes affect the Rs dynamics in different stages of the alpine meadow underlain by permafrost in the Qinghai–Tibet Plateau (QTP). We conducted continuous in situ measurements of Rs and freeze–thaw processes of the active layer at an alpine meadow site in the Beiluhe permafrost region of the QTP and divided the freeze–thaw processes into four different stages in a complete freeze–thaw cycle, comprising the summer thawing (ST) stage, autumn freezing (AF) stage, winter cooling (WC) stage, and spring warming (SW) stage. We found that the freeze–thaw processes have various effects on the Rs dynamics in different freeze–thaw stages. The mean Rs ranged from 0.12 to 3.18 µmol m−2 s−1 across the stages, with the lowest value in WC and highest value in ST. Q10 among the different freeze–thaw stages changed greatly, with the maximum (4.91±0.35) in WC and minimum (0.33±0.21) in AF. Patterns of Rs among the ST, AF, WC, and SW stages differed, and the corresponding contribution percentages of cumulative Rs to total Rs of a complete freeze–thaw cycle (1692.98±51.43 g CO2 m−2) were 61.32±0.32 %, 8.89±0.18 %, 18.43±0.11 %, and 11.29±0.11 %, respectively. Soil temperature (Ts) was the most important driver of Rs regardless of soil water status in all stages. Our results suggest that as climate change and permafrost degradation continue, great changes in freeze–thaw process patterns may trigger more Rs emissions from this ecosystem because of a prolonged ST stage.

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Slope hydrology as influenced by thawing of the active layer, Resolute, N.W.T.

Canadian Journal of Earth Sciences ◽

10.1139/e83-087 ◽

1983 ◽

Vol 20 (6) ◽

pp. 978-986 ◽

Cited By ~ 51

Author(s):

Ming-ko Woo ◽

Peter Steer

Keyword(s):

Surface Topography ◽

Active Layer ◽

Surface Runoff ◽

Storage Capacity ◽

Water Storage ◽

High Arctic ◽

Surface Flow ◽

Water Storage Capacity ◽

Continuous Permafrost ◽

Generate Surface

High arctic slopes have a shallow active layer that thaws unevenly during summer. The result is often a lack of agreement between the configuration of the frost table and the surface topography, and this has effects on the slope hydrology. (1) Areas with a shallow frost table favour surface runoff but areas with a deeper frost table require a thick zone of saturation to generate surface flow. Uneven thaw depths then cause alternating seepage and re-emergence of water down a slope. (2) The configuration of the frost table is highly dynamic, causing day to day changes in water storage capacity in the active layer. (3) A frost table with local depressions can pond up groundwater, which may be rapidly released when part of the frozen sill is breached by continual thawing. (4) The topographical drainage divide may not correspond with the subsurface drainage divide as defined by the frost table, thus allowing groundwater to drain laterally across topographical boundaries. These findings show that a knowledge of the frost table behaviour, both spatially and temporally, is essential to the study of slope hydrology in continuous permafrost terrains.

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Annual soil CO2 efflux in a wet meadow during active layer freeze–thaw changes on the Qinghai-Tibet Plateau

Environmental Earth Sciences ◽

10.1007/s12665-012-1970-y ◽

2012 ◽

Vol 69 (3) ◽

pp. 855-862 ◽

Cited By ~ 9

Author(s):

Junfeng Wang ◽

Qingbai Wu

Keyword(s):

Active Layer ◽

Soil Co2 Efflux ◽

Tibet Plateau ◽

Co2 Efflux ◽

Soil Co2 ◽

Wet Meadow ◽

Freeze Thaw ◽

Qinghai Tibet Plateau

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The enigma of large sorted stone stripes in the tropical Ethiopian Highlands

10.5194/egusphere-egu2020-5552 ◽

2020 ◽

Author(s):

Alexander Raphael Groos ◽

Janik Niederhauser ◽

Naki Akçar ◽

Heinz Veit

Keyword(s):

Active Layer ◽

Late Pleistocene ◽

Small Scale ◽

Mean Annual Temperature ◽

Seasonal Temperature ◽

Ethiopian Highlands ◽

Tropical Mountains ◽

Freeze Thaw ◽

Exposure Dating ◽

Ice Cap

<p>The Bale Mountains in the southern Ethiopian Highlands (7-8&#176;N) are formed of multiple superimposed flood basalts and comprise Africa&#8217;s largest plateau above 4000 m. Glacial and periglacial landforms are well-preserved and facilitate the reconstruction of the paleoclimate and landscape of the afro-alpine environment. During the Late Pleistocene, an ice cap covered the central part of the plateau and outlet glaciers extended down into the northern valleys. A striking geomorphological feature on the plateau are large sorted stone stripes that consist of hardly-weathered columnar basalt and are up to 2 m deep, 15 m wide and 200 m long. The stone stripes are located between 3850 and 4050 m at gentle slopes (4-8&#176;) of two volcanic plugs 3-5 km south of the highest peak (Tullu Dimtu, 4377 m) and in the far west of the plateau. Sorted patterned grounds of similar size are characteristic for periglacial environments of the high latitudes, but unique for tropical mountains since their formation requires permafrost and a deep active layer. While diurnal freeze-thaw cycles in tropical mountains are sufficient for the genesis of small-scale patterned grounds, the sorting of large basalt columns (length >2 m, diameter >40 cm) assumes seasonal (or multi-annual) freeze-thaw cycles and a deep active layer. When and under which climatic conditions the sorted stone stripes in the Bale Mountains formed, remains an unsolved mystery. The stone stripes might have developed during the Late Pleistocene under periglacial conditions in close proximity to the ice cap or after deglaciation (~15-14 ka). To assess the timing of the final stagnation of the stone stripes, we determined the age of six basalt columns from two different stripes using <sup>36</sup>Cl surface exposure dating. In addition, we installed temperature data logger in 2, 10 and 50 cm depth across the plateau and between the stone stripes to investigate the present thermal conditions and diurnal and seasonal temperature variations in the ground. The difference between the measured mean annual temperature and presumed average ground temperature for permafrost (&#8804;0&#176;C) indicates an extreme temperature depression on the plateau of &#8805;10&#176;C during the formation period of the sorted stone stripes. Such a Late Pleistocene cooling would be unprecendented in the tropical mountains. Finally, we applied a simple statistical model forced with meteorological data from a nearby weather station to simulate ground temperatures and test which climatic preconditions are necessary for the formation of sporadic permafrost in the Bale Mountains.</p>

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