Decadal topographic change in the McMurdo Dry Valleys of Antarctica: Thermokarst subsidence, glacier thinning, and transfer of water storage from the cryosphere to the hydrosphere

Abstract

Recent local-scale observations of glaciers, streams, and soil surfaces in the McMurdo Dry Valleys of Antarctica (MDV) have documented evidence for rapid ice loss, glacial thinning, and ground surface subsidence associated with melting of ground ice. To evaluate the extent, magnitude, and location of decadal-scale landscape change in the MDV, we collected airborne lidar elevation data in 2014-2015 and compared these data to a 2001-2002 airborne lidar campaign. This regional assessment of elevation change spans the recent acceleration of warming and melting observed by long-term meteorological and ecosystem response experiments, allowing us to assess the response of MDV surfaces to warming and potential thawing feedbacks. We find that locations of thermokarst subsidence are strongly associated with the presence of excess ground ice and with proximity to surface or shallow subsurface (active layer) water. Subsidence occurs across soil types and landforms, in low-lying, low-slope areas with impeded drainage and also high on steep valley walls. Glacier thinning is widespread and is associated with the growth of fine-scale roughness. Pond levels are rising in most closed-basin lakes in the MDV, across all microclimate zones. These observations highlight the continued importance of insolation-driven melting in the MDV. The regional melt pattern is consistent with an overall transition of water storage from the local cryosphere (glaciers, permafrost) to the hydrosphere (closed basin lakes and ponds as well as the Ross Sea). We interpret this regional melting pattern to reflect a transition to Arctic and alpine-style, hydrologically mediated permafrost and glacial melt.

Prediction of Ice‐Free Conditions for a Perennially Ice‐Covered Antarctic Lake

“…The McMurdo Dry Valleys have shown a transition from water storage in the cryosphere to the hydrosphere over the past decade due to an increased and persistent solar radiation (Levy et al, ). Decrease of both solar radiation and surface air temperature required to maintain perennial ice covers is highly unlikely under projected climate change, and our model results predict that the perennially ice‐covered lakes in this region will become seasonally ice free within this century.…”

“…Solar radiation in the McMurdo Dry Valleys has increased in the 1990s and remained relatively elevated since (Figure a), a trend attributed to geomorphic and ecological changes in the region (Fountain et al, ; Gooseff et al, ; Levy et al, ; Obryk et al, ). Surface air temperature has decreased until 2006 and exhibited high variability thereafter (Figure b).…”

Detection and community-level identification of microbial mats in the McMurdo Dry Valleys using drone-based hyperspectral reflectance imaging

“…14. This workflow allows for the detection and classification of microbial mats using either point-based or imaging reflectance spectrometers, provided the spectral resolution of the spectrometer is sufficient to capture the narrow ~667 nm absorption (Levy et al unpublished data 2018). By using low-flying point spectrometers or push-broom imagers with sufficient spatial resolution (centimetre scale), we propose that it could be possible to determine annual mat growth or reduction using this method.…”

“…Microbial mat heterogeneity is high, even over lengths scales of 1 m or less (Jungblut et al 2005, Karr et al 2005, Zeglin et al 2009). If different mat types (determined by the identity of characteristic cyanobacteria) respond rapidly and in environmentally diagnostic ways to changing physical conditions, then there is a need to be able to monitor the extent and activity of Antarctic microbial mats as a system proxy that would be useful for detecting regional changes in runoff and biogeochemistry in an environment that is on the brink of major climatic and hydrological change (Fountain et al 2014, Levy et al 2018). Critically, microbial mats in MDV streams respond rapidly, over days to weeks, to changes in water availability (McKnight et al 1999).…”

A Rapid Terrestrial Laser Scanning Method for Coastal Erosion Studies: A Case Study at Freeport, Texas, USA

“…Terrestrial laser scanning (TLS), also known as ground-based light detection and ranging (LiDAR), has become a powerful research tool for tracking ground surface deformation over time and space, such as landslide movement [1,2,3,4,5], glacial movement [6,7,8,9], faulting [10,11], and earth fissures [12]. Dense point clouds from TLS surveys provide fundamental datasets for deriving high-resolution and high-accuracy bare-earth digital elevation models (DEMs), which are essential for topographic and geomorphic studies.…”