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Borehole Temperatures Reveal Details of 20Th Century Warming at Bruce Plateau, Antarctic Peninsula : Volume 5, Issue 6 (02/11/2011)

By Zagorodnov, V.

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Book Id: WPLBN0004016915
Format Type: PDF Article :
File Size: Pages 32
Reproduction Date: 2015

Title: Borehole Temperatures Reveal Details of 20Th Century Warming at Bruce Plateau, Antarctic Peninsula : Volume 5, Issue 6 (02/11/2011)  
Author: Zagorodnov, V.
Volume: Vol. 5, Issue 6
Language: English
Subject: Science, Cryosphere, Discussions
Collections: Periodicals: Journal and Magazine Collection, Copernicus GmbH
Historic
Publication Date:
2011
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications

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Nagornov, O., Muto, A., Scambos, T. A., Zagorodnov, V., Tyuflin, S., Mosley-Thompson, E., & Pettit, E. C. (2011). Borehole Temperatures Reveal Details of 20Th Century Warming at Bruce Plateau, Antarctic Peninsula : Volume 5, Issue 6 (02/11/2011). Retrieved from http://worldebookfair.com/


Description
Description: Byrd Polar Research Center, The Ohio State University, Columbus OH 43210, USA. Two ice core boreholes of 143.74 m and 447.65 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. 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.

Summary
Borehole temperatures reveal details of 20th century warming at Bruce Plateau, Antarctic Peninsula

Excerpt
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