Early Holocene cold snaps and their expression in the moraine record of the eastern European Alps
<p>Glaciers preserve climate variations in their geological and geomorphological records, which makes them prime candidates for climate reconstructions. Investigating the glacier–climate system over the past millennia is particularly relevant first because the amplitude and frequency of natura...
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| Autores principales: | , , , , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
Copernicus Publications
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/8938fb37ed7345e29ad4dd4ad51add7a |
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| Sumario: | <p>Glaciers preserve climate variations in their geological
and geomorphological records, which makes them prime candidates for climate
reconstructions. Investigating the glacier–climate system over the past
millennia is particularly relevant first because the amplitude and
frequency of natural climate variability during the Holocene provides the
climatic context against which modern, human-induced climate change must be
assessed. Second, the transition from the last glacial to the current
interglacial promises important insights into the climate system during
warming, which is of particular interest with respect to ongoing climate
change.</p>
<p>Evidence of stable ice margin positions that record cooling during the past
12 kyr are preserved in two glaciated valleys of the Silvretta Massif in the
eastern European Alps, the Jamtal (JAM) and the Laraintal (LAR). We mapped
and dated moraines in these catchments including historical ridges using
beryllium-10 surface exposure dating (<span class="inline-formula"><sup>10</sup></span>Be SED) techniques and
correlate resulting moraine formation intervals with climate proxy records
to evaluate the spatial and temporal scale of these cold phases. The new
geochronologies indicate the formation of moraines during the early Holocene (EH), ca. 11.0 <span class="inline-formula">±</span> 0.7 ka (<span class="inline-formula"><i>n</i></span> <span class="inline-formula">=</span> 19). Boulder ages along historical moraines (<span class="inline-formula"><i>n</i></span> <span class="inline-formula">=</span> 6) suggest at least two glacier advances during the Little Ice Age (LIA; ca. 1250–1850 CE) around 1300 CE and in the second half of the 18th century. An earlier advance to the same position may have occurred
around 500 CE.</p>
<p>The Jamtal and Laraintal moraine chronologies provide evidence that
millennial-scale EH warming was superimposed by centennial-scale cooling.
The timing of EH moraine formation coincides with brief temperature drops
identified in local and regional paleoproxy records, most prominently with
the Preboreal Oscillation (PBO) and is consistent with moraine deposition
in other catchments in the European Alps and in the Arctic region. This
consistency points to cooling beyond the local scale and therefore a
regional or even hemispheric climate driver. Freshwater input sourced from
the Laurentide Ice Sheet (LIS), which changed circulation patterns in the
North Atlantic, is a plausible explanation for EH cooling and moraine
formation in the Nordic region and in Europe.</p> |
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