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| Titel |
Modelled glacier equilibrium line altitudes during the mid-Holocene in the southern mid-latitudes |
| VerfasserIn |
C. Bravo, M. Rojas, B. M. Anderson, A. N. Mackintosh, E. Sagredo, P. I. Moreno |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 11, no. 11 ; Nr. 11, no. 11 (2015-11-26), S.1575-1586 |
| Datensatznummer |
250117461
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| Publikation (Nr.) |
 copernicus.org/cp-11-1575-2015.pdf |
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| Zusammenfassung |
Glacier behaviour during the mid-Holocene (MH, 6000 years BP) in the
Southern Hemisphere provides observational data to constrain our
understanding of the origin and propagation of palaeoclimate signals. In this
study we examine the climatic forcing of glacier response in the MH by
evaluating modelled glacier equilibrium line altitudes (ELAs) and climatic
conditions during the MH compared with pre-industrial time (PI, year 1750).
We focus on the middle latitudes of the Southern Hemisphere, specifically
Patagonia and the South Island of New Zealand. Climate conditions for the MH
were obtained from PMIP2 model simulations, which in turn were used to
force a simple glacier mass balance model to simulate changes in ELA. In
Patagonia, the models simulate colder conditions during the MH in
austral summer (−0.2 °C), autumn (−0.5 °C), and winter
(−0.4), and warmer temperatures (0.2 °C) during spring. In the
Southern Alps the models show colder MH conditions in autumn (−0.7 °C) and winter (−0.4 °C), warmer conditions in spring
(0.3 °C), and no significant change in summer temperature.
Precipitation does not show significant changes but exhibits a seasonal
shift, with less precipitation from April to September and more precipitation
from October to April during the MH in both regions. The mass balance model
simulates a climatic ELA that is 15–33 m lower during the MH compared with
PI conditions. We suggest that the main causes of this difference are driven
mainly by colder temperatures associated with the MH simulation. Differences
in temperature have a dual effect on glacier mass balance: (i) less energy
is available for ablation during summer and early autumn and (ii) lower
temperatures cause more precipitation to fall as snow rather than rain in
late autumn and winter, resulting in more accumulation and higher surface
albedo. For these reasons, we postulate that the modelled ELA changes,
although small, may help to explain larger glacier extents observed by 6000 years BP in South America and New Zealand. |
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