Why do the dark and light ogives of Forbes bands have similar surface mass balances?

Band ogives are a striking and enigmatic feature of Mer de Glace glacier flow. The surface mass balances (SMBs) of these ogives have been thoroughly investigated over a period of 12 years. We find similar cumulative SMBs over this period, ranging between −64.1 and −66.2 m w.e., on the dark and light...

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Bibliographic Details
Published inJournal of glaciology Vol. 64; no. 244; pp. 236 - 246
Main Authors VINCENT, C., DUMONT, M., SIX, D., BRUN, F., PICARD, G., ARNAUD, L.
Format Journal Article
LanguageEnglish
Published Cambridge, UK Cambridge University Press 01.04.2018
Subjects
Ablation
Aerodynamics
Aerosol effects
Albedo
Albedo (solar)
Computational fluid dynamics
Cryosphere
energy balance
Glacial drift
glacier ablation phenomena
Glacier flow
glacier mass balance
Glaciers
Hypotheses
Ice
Light
Mathematical models
melt-surface
Modelling
mountain glaciers
Ogives
Radiation
Radiative forcing
Roughness
Short wave radiation
Turbulent fluxes
France
Alps
glacier ablation phenomena
energy balance
melt-surface
mountain glaciers
glacier mass balance
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Summary:Band ogives are a striking and enigmatic feature of Mer de Glace glacier flow. The surface mass balances (SMBs) of these ogives have been thoroughly investigated over a period of 12 years. We find similar cumulative SMBs over this period, ranging between −64.1 and −66.2 m w.e., on the dark and light ogives even though the dark ogive albedo is ~40% lower than that of the light ogives. We, therefore, looked for another process that could compensate for the large difference of absorbed short-wave radiation between dark and light ogives. Based on in situ roughness measurements, our numerical modeling experiments demonstrate that a significant difference in turbulent flux over the dark and light ogives due to different surface roughnesses could compensate for the difference in radiative forcing. Our results discard theories for the genesis of band ogives that are based on the assumption of a strong ice ablation contrast between dark and light ogives. More generally, our study demonstrates that future roughness changes are as important to analyze as the radiative impacts of a potential increase of aerosols or debris at the surface of glaciers.
ISSN:0022-1430
1727-5652
DOI:10.1017/jog.2018.12