Monitoring freeze—thaw cycles along North—South Alaskan transects using ERS-1 SAR

Rignot, Eric; Way, J.

doi:10.1016/0034-4257(94)90049-3

Cited by 105 publications

(44 citation statements)

References 16 publications

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“…Monitoring of soil freezing and thawing states on large scales with high spatial and temporal resolution is especially important in high latitude ecosystems, as they affect the length of the growth season, the net primary production of organic matter, the carbon balance as well as frost damage on plants [1][2][3][4][5]. This requires an effective monitoring system, which is able to map the phase transitions within the soil and to monitor the extent as well as the temporal dynamics of the active layer in permafrost regions [6].…”

Section: Introductionmentioning

confidence: 99%

Identification of Soil Freezing and Thawing States Using SAR Polarimetry at C-Band

et al. 2014

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Abstract:The monitoring of soil freezing and thawing states over large areas is very challenging on ground. In order to investigate the potential and the limitations of space-borne SAR polarimetry at C-band for soil state survey, analyses were conducted on an entire winter time series of fully polarimetric RADARSAT-2 data from 2011/2012 to identify freezing as well as thawing states within the soil. The polarimetric data were acquired over the Sodankylä test site in Finland together with in situ measurements of the soil and the snow cover. The analyses indicate clearly that the dynamics of the polarimetric entropy and mean scattering alpha angle are directly correlated to soil freezing and thawing states, even under distinct dry snow cover. First modeling attempts using the Extended Bragg soil scattering model justify the observed trends, which indicate surface-like scattering during frozen soil conditions and multiple/volume scattering for thawed soils. Hence, these first investigations at C-band foster motivation to work towards a robust polarimetric detection of soil freezing and thawing states as well as their transition phase.

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Section: Introductionmentioning

confidence: 99%

Identification of Soil Freezing and Thawing States Using SAR Polarimetry at C-Band

et al. 2014

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“…We believe that the surface water in the sedge fen was not completely frozen on 9 November. Radar backscatter can increase with freezing in areas of standing water, including wetlands, due to the formation of a rough ice-water or ice-soil interface [49]. During freezing conditions, the rate of decrease in the ERS-2 backscatter was more rapid at BR and SII and more gradual at FI, FII, and T, suggesting that areas with poor insulation from shallow snow cover are differentially frozen versus areas with greater snow accumulation and higher surface soil temperature.…”

Section: The Effect Of Soil Freezing On Backscatter In Autumn and Earmentioning

confidence: 99%

C-Band SAR Imagery for Snow-Cover Monitoring at Treeline, Churchill, Manitoba, Canada

Pivot

2012

Remote Sensing

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RADARSAT and ERS-2 data collected at multiple incidence angles are used to characterize the seasonal variations in the backscatter of snow-covered landscapes in the northern Hudson Bay Lowlands during the winters of 1997/98 and 1998/99. The study evaluates the usefulness of C-band SAR systems for retrieving the snow water equivalent under dry snow conditions in the forest-tundra ecotone. The backscatter values are compared against ground measurements at six sampling sites, which are taken to be representative of the land-cover types found in the region. The contribution of dry snow to the radar return is evident when frost penetrates the first 20 cm of soil. Only then does the backscatter respond positively to changes in snow water equivalent, at least in the open and forested areas near the coast, where 1-dB increases in backscatter for each approximate 5-10 mm of accumulated water equivalent are observed at 20-31 incidence angles. Further inland, the backscatter shows either no change or a negative change with snow accumulation, which suggests that the radar signal there is dominated by ground surface scattering (e.g., fen) when not attenuated by vegetation (e.g., forested and transition). With high-frequency ground-penetrating radar, we demonstrate the presence of a 10-20-cm layer of black ice underneath the snow cover, which causes the reduced radar returns (−15 dB and less) observed in the inland fen. A correlation between the backscattering and the snow water equivalent cannot be determined due to insufficient observations at similar incidence angles. To establish a relationship between the snow water equivalent and the backscatter, only images acquired with similar incidence angles should be used, and they must be corrected for both vegetation and ground effects.

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“…Radar remote sensing, including synthetic aperture radar (SAR), has great potential to provide spatially-distributed information on permafrost ecosystem dynamics with its ability to penetrate cloud and independence from solar illumination. A number of studies using the space-borne radar measurements have been conducted to extract information regarding the freeze/thaw cycle [1][2][3][4][5][6][7], taiga forests [8][9][10][11][12][13][14], wetlands [15][16][17] and geological features [18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Variations of Microwave Scattering Properties by Seasonal Freeze/Thaw Transition in the Permafrost Active Layer Observed by ALOS PALSAR Polarimetric Data

Park

2015

Remote Sensing

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Radar backscattering properties can be extremely sensitive to the freeze/thaw states of the ground surface. This study aims to evaluate the changes of L-band microwave scattering characteristics between thawed and frozen conditions by using polarimetric scattering mechanism indicators. ALOS PALSAR polarimetric mode data acquired in winter and spring seasons over Eastern Siberia are used in this study. Experimental results show that the actual scattering mechanisms and their seasonal variations over various forested and non-forested permafrost ecosystems can be successfully characterized by the polarimetric target decomposition parameters and the polarimetric coherences. In addition, fully polarimetric radar observations exhibit great potential for mapping land cover types and surficial features in the permafrost active layer. Particularly, the co-polarization coherences on the HV-polarization basis and circular-polarization basis were found to be very useful for discriminating different surficial geocryological characteristics in recently burnt forests and thermokarst regions.

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Monitoring freeze—thaw cycles along North—South Alaskan transects using ERS-1 SAR

Abstract: Monitoring freeze-thaw cycles of high latitude terrestrial ecosystems is useful for estimating the length of the growing season and annual productivity in the tundra

Cited by 105 publications

References 16 publications

Identification of Soil Freezing and Thawing States Using SAR Polarimetry at C-Band

Identification of Soil Freezing and Thawing States Using SAR Polarimetry at C-Band

C-Band SAR Imagery for Snow-Cover Monitoring at Treeline, Churchill, Manitoba, Canada

Variations of Microwave Scattering Properties by Seasonal Freeze/Thaw Transition in the Permafrost Active Layer Observed by ALOS PALSAR Polarimetric Data

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