Abstract
To understand the response of the Greenland ice sheet to climate change the so-called ablation zone is of particular importance, since it accommodates the yearly net surface ice loss. In numerical models and for data analysis, the bulk aerodynamic method is often used to calculate the turbulent surface fluxes, for which the aerodynamic roughness length (z 0) is a key parameter. We present, for the first time, spatial and temporal variations of z 0 in the ablation area of the Greenland ice sheet using year-round data from three automatic weather stations and one eddy-correlation mast. The temporal variation of z 0 is found to be very high in the lower ablation area (factor 500) with, at the end of the summer melt, a maximum in spatial variation for the whole ablation area of a factor 1000. The variation in time matches the onset of the accumulation and ablation season as recovered by sonic height rangers. During winter, snow accumulation and redistribution by snow drift lead to a uniform value of z 0≈ 10−4 m throughout the ablation area. At the beginning of summer, snow melt uncovers ice hummocks and z 0 quickly increases well above 10−2 m in the lower ablation area. At the end of summer melt, hummocky ice dominates the surface with z 0 > 5 × 10−3 m up to 60 km from the ice edge. At the same time, the area close to the equilibrium line (about 90 km from the ice edge) remains very smooth with z 0 = 10−5 m. At the beginning of winter, we observed that single snow events have the potential to lower z 0 for a very rough ice surface by a factor of 20 to 50. The total surface drag of the abundant small-scale ice hummocks apparently dominates over the less frequent large domes and deep gullies. The latter results are verified by studying the individual drag contributions of hummocks and domes with a drag partition model.
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References
Alley RB, Clark PU, Huybrechts P, Joughin I (2005) Ice-sheet and sea-level changes. Science 310: 456–460
Ambach W (1977a) Untersuchungen zum energieumsatz in der ablationszone des grönländischen inlandeis, expedition glaciologique internationale au groenland. Bianco Lunos Bogtryyeri A/S, Kobenhagen 4(5): 63
Ambach W (1977b) Untersuchungen zum energieumsatz in der akkumulationszone des grönländischen inlandeis, expedition glaciologique internationale au groenland. Bianco Lunos Bogtryyeri A/S, Kobenhagen 4(7): 44
Andreas EL (1995) Air-ice drag coefficients in the western weddell sea. 2. A model based on form drag and drifting snow. J Geophys Res 100(C3): 4833–4843
Andreas EL (2002) Parameterizing scalar tranfer over snow and ice: a review. J Hydrol 3: 417–432
Andreas EL, Claffey KJ (1995) Air-ice drag coefficients in the western weddell sea. 1. Values deduced from profile measurements. J Geophys Res 100(C3): 4821–4831
Andreas EL, Lange MA, Ackley SF, Wadhams P (1993) Roughness of weddel sea ice and estimates of the air-ice drag coefficients. J Geophys Res 98: 12,439–12,452
Banke E, Smith S, Anderson R (1980) Drag coefficients at aidjex from sonic anemometer measurements. In: Pritchard R (ed) Sea ice processes and models. University of Washington Press, pp 430–442
Blackader AK, Tennekes H (1968) Asymptotic similarity in neutral barotropic boundary layers. J Atmos Sci 25: 1015–1020
Box J (2002) Survey of greenland instrumental temperature records. Int J Clim 22: 1828–1847
Businger JA, Wyngaard JC, Izumi Y, Bradley EF (1971) Flux-profile relationships in the atmospheric boundary layer. J Atmos Sci 30: 788–794
Castro IP, Cheng H, Reynolds R (2006) Turbulence over urban-type roughness: deductions from wind-tunnel measurements. Boundary–Layer Meteorol 118: 109–131
Coceal O, Thomas TG, Belcher SE (2007) Spatial variability of flow statistics within regular building arrays. Boundary–Layer Meteorol 125: 537–552
Crawley DM, Nickling WG (2002) Drag partition for regularly-arrayed rough surfaces. Boundary–Layer Meteorol 107: 445–468
Denby B, Smeets CJPP (2000) Derivation of turbulent flux profiles and roughness lengths from katabatic flow dynamics. J Appl Meteorol 39: 1601–1612
Duynkerke PG, Van den Broeke MR (1994) Surface energy balance and katabatic flow over glacier and tundra during GIMEX-91. Glob Planet Change 9: 17–28
Forrer J, Rotach MW (1997) On the turbulence structure in the stable boundary layer over the greenland ice sheet. Boundary–Layer Meteorol 85: 111–136
Fritschen LJ, Gay LW (1979) Environmental instrumentation. Springer-Verlag, New York 216 pp
Grimmond CSB, Oke TR (1999) Aerodynamic properties of urban areas derived from analysis of surface form. J Appl Meteorol 38: 1262–1292
Heinemann G (1999) The KABEG’97 experiment: an aircraft-based study of katabatic wind dynamics over the greenland ice sheet. Boundary–Layer Meteorol 93: 75–116
Heinemann G, Falk U (2002) Surface winds and energy fluxes near the greenland ice margin. Polarforchung 71: 15–31
Jackson BS, Carroll JJ (1978) Aerodynamic roughness as a function of wind direction over asymmetric surface elements. Boundary–Layer Meteorol 14: 323–330
Jacobs AFG, McNaughton KG (1994) The excess temperature of a rigid fast–response thermometer and its effects on measured heat flux. J Atmos Oceanic Technol 11(3): 680–686
Joffre SM (1982) Momentum and heat transfers in the surface layer over a frozen sea. Boundary–Layer Meteorol 24:211–229
Kaimal J, Finnigan J (1994) Atmospheric boundary layer flows, 1st edn. Oxford University Press, Cambridge atmospheric and space science series, New York 289 pp
Langleben MP (1974) On wind profiles over sea ice (and discussion with c. a. paulson and n. understeiner). Geophys Res Lett 1: 82–85, 313–315
Makin VK, Kudryavtsev VN (1999) Coupled sea surface-atmosphere model, 1, wind over waves coupling. J Geophys Res 104(C4): 7613–7623
Meesters AGCA, Bink NJ, Vugts HF, Cannemeijer F, Henneken EAC (1997) Turbulence observations above a smooth melting surface on the greenland ice sheet. Boundary–Layer Meteorol 85: 81–110
Moore CJ (1986) Frequency response corrections for eddy correlation’s systems. Boundary–Layer Meteorol 37: 17–35
Munro DS, Davies JA (1978) On fitting the log-linear model to wind speed and temperature profiles over a melting glacier. Boundary–Layer Meteorol 15: 423–437
Oerlemans J, Vugts HF (1993) A meteorological experiment in the melting zone of the greenland ice-sheet. Bull Amer Meteorol Soc 74(3): 355–365
Owen PR (1964) Saltation of uniform grains in air. J Fluid Mech 20: 225–242
Pandolfo JP (1966) Wind and temperature for constant flux boundary layers in lapse conditions with a variable eddy conductivity to eddy viscosity ratio. J Atmos Sci 23: 495–502
Raupach MR (1992) Drag and drag partition on rough surfaces. Boundary–Layer Meteorol 60: 375–395
Raupach MR (1994) Simplified expressions for vegetation roughness length and zero–plane displacement as functions of canopy height and area index. Boundary–Layer Meteorol 71: 211–216
Raupach MR, Thom AS, Edwards I (1980) A wind–tunnel study of turbulent flow close to regular arrayed rough surfaces. Boundary–Layer Meteorol 18: 373–397
Rignot E, Kanagaratnam P (2006) Changes in the velocity structure of the greenland ice sheet. Science 311(5763): 986–990
Schotanus P, Nieuwstadt FTM, de Bruin HAR (1983) Temperature measurement with a sonic anemometer and its application to heat and moisture fluxes. Boundary–Layer Meteorol 26: 81–93
Shao Y, Yang Y (2005) A scheme for drag partition over rough surfaces. Atmos Environ 39: 7351–7361
Smeets CJPP, Duynkerke PG, Vugts HF (1998) Turbulence characteristics of the stable boundary layer over a mid-latitude glacier. part I: a combination of katabatic and large-scale forcing. Boundary–Layer Meteorol 87: 117–145
Smeets CJPP, Duynkerke PG, Vugts HF (1999) Observed wind profiles and turbulence fluxes over an ice surface with changing surface roughness. Boundary–Layer Meteorol 92: 101–123
Steffen K, Box J (2001) Surface climatology of the greenland ice sheet: greenland climate network 1995–1999. J Geophys Res 106(D24): 33,951–33,964
Thom AS (1971) Momentum absorbtion by vegetation. Quart J Roy Meteorol Soc 97: 414–428
Velicogna I, Wahr J (2006) Acceleration of greenland ice mass loss in spring 2004. Nature 443: 329–331
Van den Broeke MR (1996) Characteristics of the lower ablation zone of the west greenland ice sheet for energy-balance modelling. Annals Geophysica 23: 160–166
Van den Broeke MR, Duynkerke PG, Oerlemans J (1994) The observed katabatic flow at the edge of the greenland ice sheet during GIMEX-91. Global Planetary Change 9: 3–15
Van de Wal RSW, Greuell MR, van den Broeke MR, Reijmer CH, Oerlemans J (2005) Surface mass balance observations and automatic weather station data along a transect near kangerlussuaq, west greenland. Ann Glaciol 42: 311–316
Wieringa J (1993) Representative roughness parameters for homogeneous terrain. Boundary–Layer Meteorol 63: 323–363
Wilczak JM, Oncley SP, Stage SA (2001) Sonic anemometer tilt correction algorithms. Boundary–Layer Meteorol 99: 127–150
Acknowledgments
We would like to thank the IMAU technicians for designing and maintaining the AWS and turbulence stations, and all the people involved in the data collection. Furthermore, the comments from two anonymous referees are very much appreciated. This work is funded by the Utrecht University and the Netherlands Polar Program (NPP) of the Netherlands Organisation of Scientific Research, section Earth and Life Sciences (NWO/ALW).
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Open Access This is an open access article distributed under the terms of the Creative Commons Attribution Noncommercial License (https://creativecommons.org/licenses/by-nc/2.0), which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.
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Smeets, C.J.P.P., van den Broeke, M.R. Temporal and Spatial Variations of the Aerodynamic Roughness Length in the Ablation Zone of the Greenland Ice Sheet. Boundary-Layer Meteorol 128, 315–338 (2008). https://doi.org/10.1007/s10546-008-9291-0
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DOI: https://doi.org/10.1007/s10546-008-9291-0