Where is the 1-million-year-old ice at Dome A?
Ice fabric influences the rheology of ice, and hence the age–depth profile at ice core drilling sites. To investigate the age–depth profile to be expected of the ongoing deep ice coring at Kunlun station, Dome A, we use the depth-varying anisotropic fabric suggested by the recent polarimetric meas...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-05-01
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| Series: | The Cryosphere |
| Online Access: | https://www.the-cryosphere.net/12/1651/2018/tc-12-1651-2018.pdf |
| _version_ | 1819095098380517376 |
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| author | L. Zhao L. Zhao J. C. Moore J. C. Moore J. C. Moore B. Sun X. Tang X. Guo |
| author_facet | L. Zhao L. Zhao J. C. Moore J. C. Moore J. C. Moore B. Sun X. Tang X. Guo |
| author_sort | L. Zhao |
| collection | DOAJ |
| description | Ice fabric influences the rheology of ice, and hence the age–depth profile at
ice core drilling sites. To investigate the age–depth profile to be expected
of the ongoing deep ice coring at Kunlun station, Dome A, we use the depth-varying anisotropic fabric suggested by the recent polarimetric measurements
around Dome A along with prescribed fabrics ranging from isotropic through
girdle to single maximum in a three-dimensional, thermo-mechanically coupled
full-Stokes model of a 70 × 70 km<sup>2</sup> domain around Kunlun
station. This model allows for the simulation of the near basal ice temperature and
age, and ice flow around the location of the Chinese deep ice coring site.
Ice fabrics and geothermal heat flux strongly affect the vertical advection
and basal temperature which consequently control the age profile.
Constraining modeled age–depth profiles with dated radar isochrones to 2∕3
ice depth, the surface vertical velocity, and also the spatial variability of
a radar isochrones dated to 153.3 ka BP, limits the age of the deep ice at
Kunlun to between 649 and 831 ka, a much smaller range than previously inferred. The
simple interpretation of the polarimetric radar fabric data that we use
produces best fits with a geothermal heat flux of 55 mW m<sup>−2</sup>. A heat
flux of 50 mW m<sup>−2</sup> is too low to fit the deeper radar layers, and 60 mW m<sup>−2</sup> leads to unrealistic surface velocities. The
modeled basal temperature at Kunlun reaches the pressure melting point with a
basal melting rate of 2.2–2.7 mm a<sup>−1</sup>. Using the spatial distribution
of basal temperatures and the best fit fabric suggests that within 400 m of
Kunlun station, 1-million-year-old ice may be found 200 m above the bed, and that
there are large regions where even older ice is well above the bedrock within
5–6 km of the Kunlun station. |
| first_indexed | 2024-12-21T23:37:54Z |
| format | Article |
| id | doaj.art-db21c11404f74b74a47a4596f570356b |
| institution | Directory Open Access Journal |
| issn | 1994-0416 1994-0424 |
| language | English |
| last_indexed | 2024-12-21T23:37:54Z |
| publishDate | 2018-05-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | The Cryosphere |
| spelling | doaj.art-db21c11404f74b74a47a4596f570356b2022-12-21T18:46:19ZengCopernicus PublicationsThe Cryosphere1994-04161994-04242018-05-01121651166310.5194/tc-12-1651-2018Where is the 1-million-year-old ice at Dome A?L. Zhao0L. Zhao1J. C. Moore2J. C. Moore3J. C. Moore4B. Sun5X. Tang6X. Guo7College of Global Change and Earth System Science, Beijing Normal University, Beijing 100875, ChinaJoint Center for Global Change Studies (JCGCS), Beijing 100875, ChinaCollege of Global Change and Earth System Science, Beijing Normal University, Beijing 100875, ChinaJoint Center for Global Change Studies (JCGCS), Beijing 100875, ChinaArctic Centre, University of Lapland, P.O. Box 122, 96101 Rovaniemi, FinlandPolar Research Institute of China, Shanghai 200129, ChinaPolar Research Institute of China, Shanghai 200129, ChinaCollege of Global Change and Earth System Science, Beijing Normal University, Beijing 100875, ChinaIce fabric influences the rheology of ice, and hence the age–depth profile at ice core drilling sites. To investigate the age–depth profile to be expected of the ongoing deep ice coring at Kunlun station, Dome A, we use the depth-varying anisotropic fabric suggested by the recent polarimetric measurements around Dome A along with prescribed fabrics ranging from isotropic through girdle to single maximum in a three-dimensional, thermo-mechanically coupled full-Stokes model of a 70 × 70 km<sup>2</sup> domain around Kunlun station. This model allows for the simulation of the near basal ice temperature and age, and ice flow around the location of the Chinese deep ice coring site. Ice fabrics and geothermal heat flux strongly affect the vertical advection and basal temperature which consequently control the age profile. Constraining modeled age–depth profiles with dated radar isochrones to 2∕3 ice depth, the surface vertical velocity, and also the spatial variability of a radar isochrones dated to 153.3 ka BP, limits the age of the deep ice at Kunlun to between 649 and 831 ka, a much smaller range than previously inferred. The simple interpretation of the polarimetric radar fabric data that we use produces best fits with a geothermal heat flux of 55 mW m<sup>−2</sup>. A heat flux of 50 mW m<sup>−2</sup> is too low to fit the deeper radar layers, and 60 mW m<sup>−2</sup> leads to unrealistic surface velocities. The modeled basal temperature at Kunlun reaches the pressure melting point with a basal melting rate of 2.2–2.7 mm a<sup>−1</sup>. Using the spatial distribution of basal temperatures and the best fit fabric suggests that within 400 m of Kunlun station, 1-million-year-old ice may be found 200 m above the bed, and that there are large regions where even older ice is well above the bedrock within 5–6 km of the Kunlun station.https://www.the-cryosphere.net/12/1651/2018/tc-12-1651-2018.pdf |
| spellingShingle | L. Zhao L. Zhao J. C. Moore J. C. Moore J. C. Moore B. Sun X. Tang X. Guo Where is the 1-million-year-old ice at Dome A? The Cryosphere |
| title | Where is the 1-million-year-old ice at Dome A? |
| title_full | Where is the 1-million-year-old ice at Dome A? |
| title_fullStr | Where is the 1-million-year-old ice at Dome A? |
| title_full_unstemmed | Where is the 1-million-year-old ice at Dome A? |
| title_short | Where is the 1-million-year-old ice at Dome A? |
| title_sort | where is the 1 million year old ice at dome a |
| url | https://www.the-cryosphere.net/12/1651/2018/tc-12-1651-2018.pdf |
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