運用電阻率成像和透地雷達在極區調查永凍土：以挪威斯瓦爾巴群島為例

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Title:	運用電阻率成像和透地雷達在極區調查永凍土：以挪威斯瓦爾巴群島為例
Authors:	陳穎龍;Chen, Yin-Long
Contributors:	地球科學學系
Keywords:	二維地電阻影像法;透地雷達;永凍層;斯匹次卑爾根島;卡菲耶拉平原
Date:	2024-07-24
Issue Date:	2024-10-09 15:38:40 (UTC+8)
Publisher:	國立中央大學
Abstract:	北極圈內的斯匹次卑爾根島（Spitsbergen）隸屬於斯瓦爾巴群島（Svalbard），其地理位置坐落在極圈內。近年來，氣候變遷導致極圈氣候條件大幅改變，進而影響地表下永凍層（Permafrost）和活動層（Active layer）的分布。為了監測和分析永凍層及活動層的變化，我們分別於2022年和2023年夏季在斯匹次卑爾根島西北方卡菲耶拉（Kaffiørya）平原海岸線附近進行地球物理探勘，使用了二維地電阻影像法（ERI）和透地雷達（GPR）。我們的研究分為兩條測線施測。一條從波蘭哥白尼大學極地研究站向海岸線延伸140公尺，為垂直海岸線的長測線，該測線在2022年和2023年均進行了重複測量。2023年新增了一條與長測線相交的40公尺短測線，以及極地研究站旁苔原上的五條平行測線。靠近海岸的短測線經過極地研究站的氣象測站，目的是了解永凍層在不同方向上的分布情況。苔原上的五條平行測線間隔為1公尺，長度為40公尺。除了進行二維剖面外，我們還建立了此區域的三維模型，以更清楚了解電阻率的趨勢。本研究中，地電阻法使用溫奈陣列（Wenner Array），電極間距為1公尺，以獲取較佳的解析度成像。透地雷達則使用頻率100MHz的天線。研究結果顯示，2023年長測線的地電阻剖面相比2022年，明顯低電阻率區域增多，高電阻率區域減少，在氣象站資料中觀察到，2023年地表溫度與含水量皆為上升趨勢，可推測為氣溫上升造成降雨事件更為頻繁，造成原先高電阻區域的未飽和沉積物含水量上升，降低了電阻率。在透地雷達剖面中也可見，測線前半段訊號衰減迅速，因為含水量高導致訊號衰減快，後半段則可見強烈訊號反射，這是由於訊號反射自活動層與永凍層的介質差異。此外，短測線和苔原上的地電阻剖面顯示出高電阻率與低電阻率的明顯邊界，顯示活動層的深度大約在深度1.3公尺之間，而在深度4~5公尺處有一中高阻區域，推測為永凍層所在位置。而苔原的的結果顯示活動層深度為1.4公尺，且在深度4.5公尺處也同樣發現有此中高阻區域。這些結果表明，地電阻以及透地雷達方法可以讓我們對活動層跟永凍層分布有更多的資訊跟認知。 ;Spitsbergen Island, part of the Svalbard archipelago, is located within the Arctic Circle. In recent years, climate change has significantly altered the climatic conditions in the polar region, affecting the distribution of permafrost and the active layer. To monitor and analyze the changes in the permafrost and active layer, we conducted geophysical surveys near the coastal plains of Kaffiørya in northwestern Spitsbergen during the summers of 2022 and 2023, using two-dimensional Electrical Resistivity Imaging (ERI) and Ground Penetrating Radar (GPR). Our study involved two survey lines. One was a long line extending 140 meters from the Polish Polar Station towards the coastline, perpendicular to the shore, and was measured in both 2022 and 2023. In 2023, we added a 40-meter short line intersecting the long line, as well as five parallel survey lines on the tundra adjacent to the Polar Station. The short line near the coast passed through the meteorological station of the Polar Station to understand the distribution of permafrost in different directions. The five parallel survey lines on the tundra were spaced 1 meter apart and were each 40 meters long. In addition to conducting two-dimensional profiling, we also developed a three-dimensional model of this area to gain a clearer understanding of the resistivity trends. In this study, the electrical resistivity method employed a Wenner array with an electrode spacing of 1 meter to obtain better resolution imaging. The Ground Penetrating Radar used a 100 MHz antenna. The results of the study showed that, compared to 2022, the resistivity profile of the long line in 2023 displayed more low-resistivity areas and fewer high-resistivity areas. Meteorological data indicated an increase in both surface temperature and moisture content in 2023. It can be inferred that rising temperatures have caused more frequent rainfall events, turning previously high-resistivity unsaturated sediments into saturated sediments, thereby lowering resistivity. In the GPR profile, the strong signal reflection indicates the contrast between the active layer and the permafrost. Additionally, the resistivity profiles of the short line and the tundra lines showed a clear boundary between high and low resistivity, indicating that the depth of the active layer is approximately 1.3 meters, with a moderately high resistivity zone at a depth of 4-5 meters, likely representing the permafrost. These results demonstrate that electrical resistivity and Ground Penetrating Radar methods provide valuable information and insights into the distribution of the active layer and permafrost.
Appears in Collections:	[Graduate Institute of Geophysics] Electronic Thesis & Dissertation

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