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| Titel |
A novel method of determining accumulation rates during the last glacial period at Berkner Island, West Antarctica |
| VerfasserIn |
Ashleigh Massam, Sharon Sneed, Robert Mulvaney, Paul Mayewski, Pippa Whitehouse |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250103025
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| Publikation (Nr.) |
 EGU/EGU2015-2424.pdf |
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| Zusammenfassung |
| Current standard laboratory methods offer a relatively coarse resolution for trace element
analysis of deep ice cores (around 10mm). Sub-annual measurements, which reveal
a seasonal profile of ions trapped within the ice matrix of a core, are principally
reserved for the upper depths of ice cores where compaction due to vertical strain has
not reduced the annual layer thickness to values smaller than the typical sampling
resolution. Recent improvements in the resolution of direct elemental analysis were
demonstrated during a pilot experiment undertaken at the WM Keck Laser Ice Facility
using a prototype Sayre CellTM combined with a laser ablation inductively-coupled
plasma mass spectrometer (LA ICP-MS), which was used to carry out ultra-high
resolution trace element analysis of ice. As part of this study, this technique was used to
obtain a sub-annual view of the onset of the current interglacial period, at circa
11.6 ka BP, as recorded in the Greenland Ice Sheet Project II (GISP2) ice core.
Results demonstrated the viability of this method as a technique to extract ultra-high
resolution, sub-annual signals of multiple trace elements along an ice core with minimal
damage.
We have extended the remit of these studies by undertaking ultra-high resolution
analysis of ice originally deposited during the Holocene and the last glacial period
at the low-accumulation site at Berkner Island, in the Weddell Sea, Antarctica.
Sections of ice, taken from two depths (494-498m; 694-696m) from the Berkner Island
ice core, were analysed in order to assess the viability of the LA ICP-MS method
on ice from a low-accumulation site. A full climate profile has been obtained at
sub-annual view for both Holocene and glacial conditions, where layer thickness is
estimated to be ~5mm and hence beyond the current limit of standard chemical
analysis.
One potential outcome of this development in direct elemental analysis is the ability to
directly determine layer thicknesses at greater depths within the ice sheet – a particular issue
in Antarctica where accumulation rates can be very low. In addition, this is the only
study so far that is able to evaluate the empirical relationships used in modelled
reconstructions of glacial conditions, by comparing modelled glaciological profiles with the
profiles derived from the ultra-high resolution trace element analysis. The ultimate
outcome of this research is the construction of a more robust age-depth profile which
will enable better insight and comprehension of past climate conditions including
palaeoaccumulation.
The authors acknowledge funding from a NERC DTG studentship, with support from the
Antarctic Science bursary, the WM Keck Foundation and the US National Science
Foundation. |
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