Estimates of late Cenozoic climate change relevant to Earth surface processes in tectonically active orogens

Abstract

Abstract. 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.

Detection and explanation of spatiotemporal patterns in Late Cenozoic palaeoclimate change relevant to Earth surface processes

“…The preferential cooling in higher latitudes during the LGM and enhanced meridional temperature gradient (e.g. Otto-Bliesner et al, 2006;Bracannot et al, 2007;Mutz et al, 2018) can be expected to result in more pronounced seasonality and thus higher variation in near-surface temperature amplitude. Inversely, the accentuated warming in higher latitudes during the (Late) Pliocene (e.g.…”

How steady are steady-state mountain belts? A reexamination of the Olympic Mountains (Washington state, USA)

“…Minor sedimentary rocks of Eocene age (Eddy et al, 2017;Tabor and Cady, 1978) are contained within the Coast Range Terrane besides the predominant ∼ 50 Ma marine and subaerial basaltic rocks (Eddy et al, 2017). Exhumation of the range commenced at 18 Ma and since 14 Ma, the orogen is presumed to be in flux steady state (Batt et al, 2001;Brandon et al, 1998;Pazzaglia and Brandon, 2001).…”

Quaternary Aeolian Landscape Development in Thar Desert and its drivers

“…3). Superimposition of the simulated past wind vectors from Mutz et al (2018) over it did not show appreciable change over the time.…”

“…One of the GCMs that adequately replicated the present wind pattern over the Thar Desert was Max Planck Institute's ECHAM5 model (Kar, 2012). Mutz et al (2018) and Mutz and Ehlers (2019) used the ECHAM5 model to simulate the climate during PLIO, LGM, MH and PI. We used their mean monthly zonal and meridional wind data at 0.75º grids (https:// esdynamics.geo.uni-tuebingen.de/wiki/), to map the mean winter, spring and pre-monsoon summer wind speed in the Thar-Megathar region during PLIO, LGM and MH as percentage of the PI distribution.…”