TY - JOUR
T1 - Relating regional and point measurements of accumulation in southwest Greenland
AU - Heilig, Achim
AU - Eisen, Olaf
AU - Schneebeli, Martin
AU - Macferrin, Michael
AU - Max Stevens, C.
AU - Vandecrux, Baptiste
AU - Steffen, Konrad
N1 - Funding Information:
Acknowledgements. We highly appreciate the work by the editor and Lynn Montgomery as well as by an anonymous referee, whose comments significantly improved the paper. Achim Heilig was supported by a DFG grant (HE 7501/1-1). Michael MacFerrin and C. Max Stevens were supported by the National Aeronautics and Space Administration (NASA) grant NNX15AC62G. We highly acknowledge support in logistics and preparation of the field campaigns from Kathy Young, Tracy Sheeley and staff from Polar Field Services. We appreciate the support by Christoph Mayer and the Geodesy and Glaciology group at the Bavarian Academy of Sciences and Humanities who provided the radar equipment in 2017 and had numerous suggestions and recommendations for improving this work. We thank Bastian Gerling, Leander Gambal, Samira Samimi, Tasha Snow and Shawn Marshall for their assistance during field seasons.
Funding Information:
(Deutsche Forschungsgemeinschaft; grant no. HE7501/1-1) and NASA (grant no. NNX15AC62G).
Publisher Copyright:
© Author(s) 2020.
PY - 2020/1/31
Y1 - 2020/1/31
N2 - In recent decades, the Greenland ice sheet (GrIS) has frequently experienced record melt events, which have significantly affected surface mass balance (SMB) and estimates thereof. SMB data are derived from remote sensing, regional climate models (RCMs), firn cores and automatic weather stations (AWSs). While remote sensing and RCMs cover regional scales with extents ranging from 1 to 10 km, AWS data and firn cores are point observations. To link regional scales with point measurements, we investigate the spatial variability of snow accumulation (bs) within areas of approximately 1-4 km2 and its temporal changes within 2 years of measurements. At three different sites on the southwestern GrIS (Swiss Camp, KAN-U, DYE-2), we performed extensive ground-penetrating radar (GPR) transects and recorded multiple snow pits. If the density is known and the snowpack dry, radar-measured two-way travel time can be converted to snow depth and bs.We spatially filtered GPR transect data to remove small-scale noise related to surface characteristics. The combined uncertainty of bs from density variations and spatial filtering of radar transects is at 7 %- 8% per regional scale of 1-4 km2. Snow accumulation from a randomly selected snow pit is very likely representative of the regional scale of 1-4 km2 (with probability p = 0:8 for a value within 10% of the regional mean for KAN-U, and p > 0:95 for Swiss Camp and DYE-2). However, to achieve such high representativeness of snow pits, it is required to determine the average snow depth within the vicinity of the pits. At DYE-2, the spatial pattern of snow accumulation was very similar for 2 consecutive years. Using target reflectors placed at respective end-of-summer-melt horizons, we additionally investigated the occurrences of lateral redistribution within one melt season.We found no evidence of lateral flow of meltwater in the current climate at DYE-2. Such studies of spatial representativeness and temporal changes in accumulation are necessary to assess uncertainties of the linkages of point measurements and regional-scale data, which are used for validation and calibration of remote-sensing data and RCM outputs.
AB - In recent decades, the Greenland ice sheet (GrIS) has frequently experienced record melt events, which have significantly affected surface mass balance (SMB) and estimates thereof. SMB data are derived from remote sensing, regional climate models (RCMs), firn cores and automatic weather stations (AWSs). While remote sensing and RCMs cover regional scales with extents ranging from 1 to 10 km, AWS data and firn cores are point observations. To link regional scales with point measurements, we investigate the spatial variability of snow accumulation (bs) within areas of approximately 1-4 km2 and its temporal changes within 2 years of measurements. At three different sites on the southwestern GrIS (Swiss Camp, KAN-U, DYE-2), we performed extensive ground-penetrating radar (GPR) transects and recorded multiple snow pits. If the density is known and the snowpack dry, radar-measured two-way travel time can be converted to snow depth and bs.We spatially filtered GPR transect data to remove small-scale noise related to surface characteristics. The combined uncertainty of bs from density variations and spatial filtering of radar transects is at 7 %- 8% per regional scale of 1-4 km2. Snow accumulation from a randomly selected snow pit is very likely representative of the regional scale of 1-4 km2 (with probability p = 0:8 for a value within 10% of the regional mean for KAN-U, and p > 0:95 for Swiss Camp and DYE-2). However, to achieve such high representativeness of snow pits, it is required to determine the average snow depth within the vicinity of the pits. At DYE-2, the spatial pattern of snow accumulation was very similar for 2 consecutive years. Using target reflectors placed at respective end-of-summer-melt horizons, we additionally investigated the occurrences of lateral redistribution within one melt season.We found no evidence of lateral flow of meltwater in the current climate at DYE-2. Such studies of spatial representativeness and temporal changes in accumulation are necessary to assess uncertainties of the linkages of point measurements and regional-scale data, which are used for validation and calibration of remote-sensing data and RCM outputs.
UR - http://www.scopus.com/inward/record.url?scp=85079006738&partnerID=8YFLogxK
U2 - 10.5194/tc-14-385-2020
DO - 10.5194/tc-14-385-2020
M3 - Article
AN - SCOPUS:85079006738
SN - 1994-0416
VL - 14
SP - 385
EP - 402
JO - Cryosphere
JF - Cryosphere
IS - 1
M1 - 385-2020
ER -
