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| Titel |
Borehole temperatures reveal details of 20th century warming at Bruce Plateau, Antarctic Peninsula |
| VerfasserIn |
V. Zagorodnov, O. Nagornov, T. A. Scambos, A. Muto, E. Mosley-Thompson, E. C. Pettit, S. Tyuflin |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1994-0416
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| Digitales Dokument |
URL |
| Erschienen |
In: The Cryosphere ; 6, no. 3 ; Nr. 6, no. 3 (2012-06-15), S.675-686 |
| Datensatznummer |
250003599
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| Publikation (Nr.) |
 copernicus.org/tc-6-675-2012.pdf |
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| Zusammenfassung |
| Two ice core boreholes of 143.18 m and 447.73 m (bedrock) were drilled
during the 2009–2010 austral summer on the Bruce Plateau at a location named
LARISSA Site Beta (66°02' S, 64°04' W, 1975.5 m a.s.l.).
Both boreholes were logged with thermistors shortly after drilling. The
shallow borehole was instrumented for 4 months with a series of resistance
thermometers with satellite uplink. Surface temperature proxy data derived
from an inversion of the borehole temperature profiles are compared to
available multi-decadal records from weather stations and ice cores located
along a latitudinal transect of the Antarctic Peninsula to West Antarctica.
The LARISSA Site Beta profiles show temperatures decreasing from the surface
downward through the upper third of the ice, and warming thereafter to the
bed. The average temperature for the most recent year is −14.78°C
(measured at 15 m depth, abbreviated T15). A minimum temperature of
−15.8°C is measured at 173 m depth, and basal temperature is
estimated to be −10.2°C. Current mean annual temperature and the
gradient in the lower part of the measured temperature profile have a best
fit with an accumulation rate of 1.9×103 kg m−2 a−1 and basal
heat flux (q) of 88 mW m−2, if steady-state conditions are assumed.
However, the mid-level temperature variations show that recent temperature
has varied significantly. Reconstructed surface temperatures
(Ts=T15) over the last 200 yr are derived by an inversion
technique (Tikhonov and Samarskii, 1990). From this, we find that cold
temperatures (minimum Ts=−16.2°C) prevailed from
~1920 to ~1940, followed by a gradual rise of
temperature to −14.2°C around 1995, then cooling over the
following decade and warming in the last few years. The coldest period was
preceded by a relatively warm 19th century at T15≥−15°C. To facilitate regional comparisons of the surface
temperature history, we use our T15 data and nearby weather station
records to refine estimates of lapse rates (altitudinal, adjusted for
latitude: Γa(l)). Good temporal and spatial consistency of
Γa(l) over the last 35 yr are observed, implying that the
climate trends observed here are regional and consistent over a broad
altitude range. |
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