Estimates of late Cenozoic climate change relevant to Earth surface processes in tectonically active orogens
The denudation history of active orogens is often interpreted in the context of modern climate gradients. Here we address the validity of this approach and ask what are the spatial and temporal variations in palaeoclimate for a latitudinally diverse range of active orogens? We do this using high...
Main Authors: | , , , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2018-04-01
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Series: | Earth Surface Dynamics |
Online Access: | https://www.earth-surf-dynam.net/6/271/2018/esurf-6-271-2018.pdf |
Summary: | The denudation history of active orogens is often interpreted in the context
of modern climate gradients. Here we address the validity of this approach
and ask what are the spatial and temporal variations in
palaeoclimate for a latitudinally diverse range of active orogens? We do this
using high-resolution (T159, ca. 80 × 80 km at the Equator) palaeoclimate
simulations from the ECHAM5 global atmospheric general circulation model and
a statistical cluster analysis of climate over different orogens (Andes,
Himalayas, SE Alaska, Pacific NW USA). Time periods and boundary conditions
considered include the Pliocene (PLIO, ∼ 3 Ma), the Last
Glacial Maximum (LGM, ∼ 21 ka), mid-Holocene (MH,
∼ 6 ka), and pre-industrial (PI, reference year 1850). The
regional simulated climates of each orogen are described by means of cluster
analyses based on the variability in precipitation, 2 m air temperature, the
intra-annual amplitude of these values, and monsoonal wind speeds where
appropriate. Results indicate the largest differences in the PI climate
existed for the LGM and PLIO climates in the form of widespread cooling and
reduced precipitation in the LGM and warming and enhanced precipitation
during the PLIO. The LGM climate shows the largest deviation in annual
precipitation from the PI climate and shows enhanced precipitation in the
temperate Andes and coastal regions for both SE Alaska and the US Pacific
Northwest. Furthermore, LGM precipitation is reduced in the western Himalayas
and enhanced in the eastern Himalayas, resulting in a shift of the wettest
regional climates eastward along the orogen. The cluster-analysis results
also suggest more climatic variability across latitudes east of the Andes in
the PLIO climate than in other time slice experiments conducted here. Taken
together, these results highlight significant changes in late Cenozoic
regional climatology over the last ∼ 3 Myr. Comparison of
simulated climate with proxy-based reconstructions for the MH and LGM reveal
satisfactory to good performance of the model in reproducing precipitation
changes, although in some cases discrepancies between neighbouring proxy
observations highlight contradictions between proxy observations themselves.
Finally, we document regions where the largest magnitudes of late Cenozoic
changes in precipitation and temperature occur and offer the highest
potential for future observational studies that quantify the impact of
climate change on denudation and weathering rates. |
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ISSN: | 2196-6311 2196-632X |