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2 results on '"CALLENS, Denis"'

1. High variability of climate and surface mass balance induced by Antarctic ice rises

Author

Lenaerts, Jan, Brown, Joel, van den Broeke, Michiel, Matsuoka, Kenichi, Drews, Reinhard, Callens, Denis, Philippe, Morgane, Gorodetskaya, I.V., van Meijgaard, E., Tijm - Reijmer, Catharina, Pattyn, F., van Lipzig, N.P.M., Sub Dynamics Meteorology, Marine and Atmospheric Research, Sub Dynamics Meteorology, and Marine and Atmospheric Research

Subjects
ice rise, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Ice stream, Antarctic sea ice, 010502 geochemistry & geophysics, 01 natural sciences, Arctic ice pack, Ice shelf, Antarctic glaciology, Climatology, Sea ice, surface mass budget, Cryosphere, Ice divide, Ice sheet, accumulation, Geology, wind-blown snow, 0105 earth and related environmental sciences, Earth-Surface Processes
Abstract

Ice rises play key roles in buttressing the neighbouring ice shelves and potentially provide palaeoclimate proxies from ice cores drilled near their divides. Little is known, however, about their influence on local climate and surface mass balance (SMB). Here we combine 12 years (2001–12) of regional atmospheric climate model (RACMO2) output at high horizontal resolution (5.5 km) with recent observations from weather stations, ground-penetrating radar and firn cores in coastal Dronning Maud Land, East Antarctica, to describe climate and SMB variations around ice rises. We demonstrate strong spatial variability of climate and SMB in the vicinity of ice rises, in contrast to flat ice shelves, where they are relatively homogeneous. Despite their higher elevation, ice rises are characterized by higher winter temperatures compared with the flat ice shelf. Ice rises strongly influence SMB patterns, mainly through orographic uplift of moist air on the upwind slopes. Besides precipitation, drifting snow contributes significantly to the ice-rise SMB. The findings reported here may aid in selecting a representative location for ice coring on ice rises, and allow better constraint of local ice-rise as well as regional ice-shelf mass balance.

Published
2014

2. Temporally stable surface mass balance asymmetry across an ice rise derived from radar internal reflection horizons through inverse modeling.

Author

CALLENS, DENIS, DREWS, REINHARD, WITRANT, EMMANUEL, PHILIPPE, MORGANE, and PATTYN, FRANK

Subjects
*MASS budget (Geophysics), *GLACIOLOGY, *ICE sheets, *ALPINE glaciers, *GROUND penetrating radar, *INTERNAL reflection spectroscopy
Abstract

Ice rises are locally grounded parts of Antarctic ice shelves that play an important role in regulating ice flow from the continent towards the ocean. Because they protrude out of the otherwise horizontal ice shelves, ice rises induce an orographic uplift of the atmospheric flow, resulting in an asymmetric distribution of the surface mass balance (SMB). Here, we combine younger and older internal reflection horizons (IRHs) from radar to quantify this distribution in time and space across Derwael Ice Rise (DIR), Dronning Maud Land, Antarctica. We employ two methods depending on the age of the IRHs, i.e. the shallow layer approximation for the younger IRHs near the surface and an optimization technique based on an ice flow model for the older IRHs. We identify an SMB ratio of 2.5 between the flanks and the ice divide with the SMB ranging between 300 and 750 kg m−2 a−1. The SMB maximum is located on the upwind side, ~4 km offset to today's topographic divide. The large-scale asymmetry is consistently observed in time until 1966. The SMB from older IRHs is less-well constrained, but the asymmetry has likely persisted for >ka, indicating that DIR has been a stable features over long time spans. [ABSTRACT FROM AUTHOR]

Published
2016
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