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TitleNear-surface temperature lapse rates over Arctic glaciers and their implications for temperature downscaling
AuthorGardner, A S; Sharp, M J; Koerner, R M; Labine, C; Boon, S; Marshall, S J; Burgess, D O; Lewis, D
SourceJournal of Climatology 2009 p. 4281-4298, Open Access logo Open Access
Alt SeriesEarth Sciences Sector, Contribution Series 20080384
PublisherAmerican Meteorological Society
Mediapaper; on-line; digital
File formatpdf
NTS39; 48H; 49; 120A
AreaEllesmere Island; Devon Island; Arctic Archipelago
Lat/Long WENS -84.0000 -70.0000 82.0000 75.0000
Subjectsenvironmental geology; temperature; glaciers; climatic fluctuations; modelling; Quaternary
Illustrationslocation maps; analyses
AbstractDistributed glacier surface melt models are often forced using air temperature fields that are either
downscaled from climate models or reanalysis, or extrapolated from station measurements. Typically, the
downscaling and/or extrapolation are performed using a constant temperature lapse rate, which is often taken
to be the free-air moist adiabatic lapse rate (MALR: 68--8C km-1). To explore the validity of this approach,
the authors examined altitudinal gradients in daily mean air temperature along six transects across four
glaciers in the Canadian high Arctic. The dataset includes over 58 000 daily averaged temperature measurements
from 69 sensors covering the period 1988--2007. Temperature lapse rates near glacier surfaces vary on
both daily and seasonal time scales, are consistently lower than theMALR(ablation seasonmean: 4.98 Ckm-1),
and exhibit strong regional covariance. A significant fraction of the daily variability in lapse rates is associated
with changes in free-atmospheric temperatures (higher temperatures 5 lower lapse rates). The temperature
fields generated by downscaling point location summit elevation temperatures to the glacier surface using
temporally variable lapse rates are a substantial improvement over those generated using the static MALR.
These findings suggest that lower near-surface temperature lapse rates can be expected under awarming climate
and that the air temperature near the glacier surface is less sensitive to changes in the temperature of the free
atmosphere than is generally assumed.

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