High Resolution Topographic Change in the McMurdo Dry Valleys of Antarctica
The McMurdo Dry Valleys (MDV), are the largest ice-sheet free region on the Antarctic continent. They are composed of mostly east-west trending valleys that separate the Ross Sea from the East Antarctic Ice Sheet. Traditionally, the MDV is a dry and stable landscape, with little annual precipitation (3-50 mm, all as snow) and a mean annual air temperature range between -14.8?C and -30.0? C. As a result of the lack of moisture, any change in the glaciers, streams and soil surface are hypothesized to be a direct result of the melting of ground ice ? an important precursor of climate change within the valleys. Multi-temporal airborne lidar (ALS) has been employed in a large scale study of the effects of climate change in the MDV. Unlike in the Arctic, the effects of climate change have not yet been widely observed in the Antarctic and changes to the region have been slower and are occurring on a smaller scale. Consequently, the high resolution provided by lidar is ideal for studying these changes and for elucidating how the continent is responding to changes in global and regional temperatures. Airborne lidar data was first collected by NASA in the austral summer of 2001/02 and a repeat data collection was made by the National Center for Airborne Laser Mapping (NCALM) in the austral summer of 2014/15. On average, the 2001/02 point cloud has a density of 0.37 points/m2 and the 2014/15 point cloud has a density of 8.8 points/m2. Despite the differing resolution of the two point clouds, they have been used to examine change across numerous scales throughout the MDV. Glacier volumes have been observed to be decreasing, though the extents of the glaciers have not significantly changed, and both lake volumes and the presence of glacial melt ponds have been observed to increase. The network of ephemeral streams and gullies that connect the glaciers and lakes show evidence of further incision between 2001/02 and 2014/15. The stream network throughout Taylor Valley, beyond those connecting major sources of water storage, has also shown widespread changes in extent and complexity, indicating further changes in groundwater transport. The soils themselves show significant subsidence both on the valley floors and in the mountainous, higher elevation terrain. These observations, examined collectively, indicate that the MDV has indeed experienced wide-spread change over the last decade. Herein, we present the methodologies used to examine temporal change in the MDV with repeat pass lidar and discuss the important initial findings of the study, including the volume losses and gains to glaciers and lakes respectively and the alteration of the ground surface. The spatial extent of these changes throughout the MDV will be highlighted to emphasize the finding that they are quite pervasive across the region, despite not being as large scale as those changes observed recently in the Arctic. Continuing work to connect evidence of temporal change to variations in the MDV microclimate, terrain slope and soil types will also be presented.