Geothermal heat flux from measured temperature profiles in deep ice boreholes in Antarctica
<p>The temperature at the Antarctic Ice Sheet bed and the temperature gradient in subglacial rocks have been directly measured only a few times, although extensive thermodynamic modeling has been used to estimate the geothermal heat flux (GHF) under the ice sheet. During the last 5 decades, de...
| Main Authors: | , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-11-01
|
| Series: | The Cryosphere |
| Online Access: | https://tc.copernicus.org/articles/14/4021/2020/tc-14-4021-2020.pdf |
| Summary: | <p>The temperature at the Antarctic Ice Sheet bed and the
temperature gradient in subglacial rocks have been directly measured only a
few times, although extensive thermodynamic modeling has been used to
estimate the geothermal heat flux (GHF) under the ice sheet. During the last
5 decades, deep ice-core drilling projects at six sites – Byrd, WAIS
Divide, Dome C, Kohnen, Dome F, and Vostok – have succeeded in reaching or nearly reaching the bed at inland locations in Antarctica. When temperature
profiles in these boreholes and steady-state heat flow modeling are combined
with estimates of vertical velocity, the heat flow at the ice-sheet base is
translated to a geothermal heat flux of 57.9 <span class="inline-formula">±</span> 6.4 mW m<span class="inline-formula"><sup>−2</sup></span> at Dome
C, 78.9 <span class="inline-formula">±</span> 5.0 mW m<span class="inline-formula"><sup>−2</sup></span> at Dome F, and 86.9 <span class="inline-formula">±</span> 16.6 mW m<span class="inline-formula"><sup>−2</sup></span>
at Kohnen, all higher than the predicted values at these sites. This warm
base under the East Antarctic Ice Sheet (EAIS) could be caused by radiogenic
heat effects or hydrothermal circulation not accounted for by the models.
The GHF at the base of the ice sheet at Vostok has a negative value of
<span class="inline-formula">−</span>3.6 <span class="inline-formula">±</span> 5.3 mW m<span class="inline-formula"><sup>−2</sup></span>, indicating that water from Lake Vostok is
freezing onto the ice-sheet base. Correlation analyses between modeled and
measured depth–age scales at the EAIS sites indicate that all of them can be
adequately approximated by a steady-state model. Horizontal velocities and
their variation over ice-age cycles are much greater for the West Antarctic
Ice Sheet than for the interior EAIS sites; a steady-state model cannot
precisely describe the temperature distribution here. Even if the
correlation factors for the best fitting age–depth curve are only moderate
for the West Antarctic sites, the GHF values estimated here of 88.4 <span class="inline-formula">±</span> 7.6 mW m<span class="inline-formula"><sup>−2</sup></span> at Byrd and 113.3 <span class="inline-formula">±</span> 16.9 mW m<span class="inline-formula"><sup>−2</sup></span> at WAIS Divide can be
used as references before more precise estimates are made on the subject.</p> |
|---|---|
| ISSN: | 1994-0416 1994-0424 |