Abstract
Knowledge of surface hydrology is essential for many applications, including studies that aim to understand permafrost response to changing climate and the associated feedback mechanisms. Advanced remote sensing techniques make it possible to retrieve a range of land-surface variables, including radar retrieved soil moisture (SSM). It has been pointed out before that soil moisture retrieval from satellite data can be challenging at high latitudes, which correspond to remote areas where ground data are scarce and the applicability of satellite data of this type is essential. This study investigates backscatter variability other than associated with changing soil moisture in order to examine the possible impact on soil moisture retrieval. It focuses on issues specific to SSM retrieval in the Arctic, notably variations related to tundra lakes. ENVISAT Advanced Synthetic Aperture Radar (ASAR) Wide Swath (WS, 120 m) data are used to understand and quantify impacts on Metop (AAdvanced Scatterometer (ASCAT, 25 km) soil moisture retrieval during the snow free period. Sites of interest are chosen according to ASAR WS availability, high or low agreement between output from the land surface model ORCHIDEE and ASCAT derived SSM. Backscatter variations are analyzed with respect to the ASCAT footprint area. It can be shown that the low model agreement is related to water fraction in most cases. No difference could be detected between periods with floating ice (in snow off situation) and ice free periods at the chosen sites. The mean footprint backscatter is however impacted by partial short term surface roughness change. The water fraction correlates with backscatter deviations (relative to a smooth water surface reference image) within the ASCAT footprint areas (R = 0.91)
Highlights
The pan-Arctic tundra lowlands are underlain by perennially frozen ground known as permafrost.Permafrost warming is ongoing and predicted to increase in magnitude over the course of the 21st century [1]
The original mean backscatter for the regions of interest (ROI) is always higher than or equal to the mean backscatter from the reference image since frozen ground conditions and spring snowmelt events have been excluded
This study examines backscatter variabilities other than related to soil moisture in order to address challenges in radar soil moisture retrieval that are specific for in the Arctic
Summary
The pan-Arctic tundra lowlands are underlain by perennially frozen ground known as permafrost. Permafrost warming is ongoing and predicted to increase in magnitude over the course of the 21st century [1]. The potential impact that thawing permafrost may have on the global climate system through the release of greenhouse gases has been a concern and a research focus since many years (e.g., [2,3]). Changes to the thermal state of permafrost are linked to rising air temperatures and variations in the precipitation. These changes to the ground thermal regime are modifying hydrological and biogeochemical dynamics [4] which are closely coupled with active layer processes [5]. The soil water content (SWC) of the active layer is a driving factor of ecosystem respiration [6] and soil moisture may be seen as a control parameter for carbon exchange with the atmosphere [7]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
