Multi-decadal surface temperature trends in East Antarctica inferred from borehole firn temperature measurements and geophysical inverse methods

Muto, Atsuhiro

Graduate Thesis Or Dissertation

Multi-decadal surface temperature trends in East Antarctica inferred from borehole firn temperature measurements and geophysical inverse methods Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/td96k2585

Abstract

The climate trend of the Antarctic interior remains unclear relative to the rest of the globe because of a lack of long-term weather records. Recent studies by other authors utilizing sparse available records, satellite data, and models have estimated a significant warming trend in the near-surface air temperature in West Antarctica and weak and poorly constrained warming trend in East Antarctica for the past 50 years. In this dissertation, firn thermal profiling was used to detect multi-decadal surface temperature trends in the interior of East Antarctica where few previous records of any kind exist. The surface temperature inversion from firn temperature profiles provides a climate reconstruction independent of firn chemistry, sparse weather data, satellite data, or ice cores, and therefore may be used in conjunction with these data sources for corroboration of climate trends over the large ice sheets. During the Norwegian-U.S. IPY Scientific Traverse of East Antarctica, in the austral summers of 2007-08 and 2008-09, thermal-profiling telemetry units were installed at five locations. Each unit consists of 16 PRTs (Platinum Resistance Thermometers) distributed in a back-filled borehole of 80 to 90 m deep. The accuracy of the temperature measurement is 0.03 K. Geophysical inverse methods (linearized and Monte Carlo inversion) were applied to one full year of data collected from three units installed near the ice divide in the Dome Fuji/ Pole of Inaccessibility region and one on Recovery Lake B, situated >500 km south to south-west of and >1000 m lower in altitude than sites near the ice divide. Three sites near the ice divide indicate that the mean surface temperatures have increased approximately 1 to 1.5 K within the past ~50 years although the onset and the duration of this warming vary by site. On the other hand, slight cooling to no change was detected at the Recovery Lake B site. Although uncertainties remain due to limitations of the method, these results raise the possibility of an interesting recent climate pattern in East Antarctica; significant warming trend near the ice divide and cooling to no change off the divide.

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