Global Positioning System interferometric reflectometry (GPS-IR) measurements of ground surface elevation changes in permafrost areas in northern Canada

Jiahua Zhang,Yufeng Hu,Lin Liu

doi:10.5194/tc-14-1875-2020

Abstract

Abstract. Global Positioning System interferometric reflectometry (GPS-IR) is a relatively new technique which uses reflected GPS signals to measure surface elevation changes to study frozen-ground dynamics. At present, more than 200 GPS stations are operating continuously in the Northern Hemisphere permafrost areas, which were originally designed and maintained for tectonic and ionospheric studies. However, only one site in Utqiaġvik, Alaska (formerly Barrow), was assessed to be usable for studying permafrost by GPS-IR. Moreover, GPS-IR has high requirements on the ground surface condition, which needs to be open, flat, and homogeneous. In this study, we screen three major GPS networks in Canada and identify 12 out of 38 stations located in permafrost areas as useful ones where reliable GPS-IR measurements can be obtained. We focus on the five Canadian Active Control System stations and obtain their daily GPS-IR surface elevation changes. We find that the ground surface subsided in Alert, Resolute Bay, and Repulse Bay respectively by 0.61±0.04 cm yr−1 (2012–2018), 0.70±0.02 cm yr−1 (2003–2014), and 0.26±0.05 cm yr−1 (2014–2019). At the other two sites of Baker Lake and Iqaluit, the trends are not statistically significant. The linear trends of deformation were negatively correlated with those of thaw indices in Alert, Resolute Bay, and Repulse Bay. Furthermore, in Resolute Bay, we also find that the end-of-thaw elevations during 2003–2012 were highly negatively correlated with the square root of thaw indices. This study is the first one using multiple GPS stations to study permafrost by GPS-IR. It highlights the multiple useful GPS stations in northern Canada, offering multi-year, continuous, and daily GPS-IR surface deformation, which provides new insights into frozen-ground dynamics at various temporal scales and across a broad region.

Highlights

Since the International Polar Year (2007–2009), permafrost has undergone a warming trend globally, with an average increase in ground temperature at or near the depth of zero annual amplitude by 0.29 ± 0.12 ◦C during 2007–2016 (Biskaborn et al, 2019; Romanovsky et al, 2010; Smith et al, 2010)
Given that the Global Positioning System interferometric reflectometry (GPS-IR) measurements of the Canadian High Arctic Ionospheric Network (CHAIN) stations might be affected by the unstable buildings, in this study we present and interpret the measured elevation changes at the five identified Canadian Active Control System (CACS) stations
We find that in Alert, Resolute Bay, and Repulse Bay, the ground surface subsided at a rate of 0.61 ± 0.04 cm yr−1 (2012–2018), 0.70 ± 0.02 cm yr−1 (2003–2014), and 0.26 ± 0.05 cm yr−1 (2014–2019), respectively

Summary

Introduction

Since the International Polar Year (2007–2009), permafrost has undergone a warming trend globally, with an average increase in ground temperature at or near the depth of zero annual amplitude by 0.29 ± 0.12 ◦C during 2007–2016 (Biskaborn et al, 2019; Romanovsky et al, 2010; Smith et al, 2010). Warming permafrost causes ground ice melting, active-layer thickening, and the release of previously sequestered carbon (Brown et al, 2000; Trucco et al, 2012). It affects hydrological, geomorphological, and biogeochemical processes (Mackay, 1966; Shur and Jorgenson, 2007; Lantuit and Pollard, 2008; Kokelj and Jorgenson, 2013). Measuring and quantifying permafrost changes are crucial for understanding the dynamics of the active-layer and near-surface permafrost (collectively called as frozen ground in this paper), studying the response of permafrost environments to climate change, and assessing the risk of permafrost changes to infrastructures. Such volume change in the freeze–thaw cycle causes the ground surface to uplift or sub-

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