Influence of Large‐Scale Atmospheric Dynamics on Precipitation Seasonality of the Tibetan Plateau and Central Asia in Cold and Warm Climates During the Late Cenozoic

Abstract

The hydroclimate of the Tibetan Plateau (TP) and Central Asia (CA) plays a crucial role in sustaining surface water reservoirs and thus water resources in the respective regions. In this study, we investigate the changes in Asian hydroclimate and its driving forces during specific time intervals in the last 3 Ma. We conduct high‐resolution (∼0.75° per grid cell) general circulation model ECHAM‐5 experiments with boundary conditions for the mid‐Pliocene (∼3 Ma), the Last Glacial Maximum (LGM; ∼21 ka), the mid‐Holocene (∼6 ka), and the pre‐industrial. Results suggest that seasonally relatively high precipitation rates (>1 mm day−1) were longer in the mid‐Pliocene and shorter in the LGM, relative to the pre‐industrial. We calculate different monsoon indices to detect changes in the intensity, strength and duration of the East Asian summer monsoon (EASM), South Asian summer monsoon (SASM), and the Indian summer monsoon (ISM), and construct climatologies of mid‐latitude high‐level westerly jet (WJ) stream occurrences based on the ECHAM5 wind fields. Our results suggest that in warm periods (e.g., mid‐Pliocene or interglacial), the WJ migrates northward earlier in the year (April) and reaches higher latitudes than in the pre‐industrial, resulting in a wetter TP and CA. During cooler periods (e.g., LGM or glacial), the WJ migrates northward later in the year (June) and remains over lower latitudes, resulting in a drier TP and CA. Increased/decreased local precipitation in TP and CA for the mid‐Pliocene/LGM experiments correlates strongly with (a) intensity, strength and duration of the EASM, SASM, and the ISM and (b) WJ latitudinal position.

South Asian summer monsoon enhanced by the uplift of Iranian Plateau in Middle Miocene

“…al., 2012;Botsyun et al, 2022b). For instance, the mid-latitude westerly Jet migrated earlier (in the year) and reached higher latitude during warm climate periods than in the pre-industry (Botsyun et al, 2022b). Our Miocene experiments likely confirm this point (not shown) but investigation in depth needs to be done in the future.…”

“…The evolution of the SASM is also largely determined by large scale circulation (Wu et. al., 2012;Botsyun et al, 2022b). For instance, the mid-latitude westerly Jet migrated earlier (in the year) and reached higher latitude during warm climate periods than in the pre-industry (Botsyun et al, 2022b).…”

West African Monsoon Dynamics and Its Control on the Stable Oxygen Isotopic Composition of Precipitation in the Late Cenozoic

“…(2018) and Botsyun et al. (2022). We build on those by simulating and analyzing the isotopic compositions for all paleoclimates.…”

“…Given the study's aim to understand the WAM response to the diverse paleoenvironmental conditions, the different experimental set-ups accounting for variations in orbital parameters, greenhouse gases concentration, SSTs, sea ice concentrations (SICs), and land surface cover (e.g., ice sheet and vegetation) were devised for the different climates. The prescribed boundary conditions for the experiments are similar to the Late Cenozoic simulations presented by Mutz et al (2018) and Botsyun et al (2022). We build on those by simulating and analyzing the isotopic compositions for all paleoclimates.…”

Impact of Quaternary Glaciations on Denudation Rates in North Pamir—Tian Shan Inferred From Cosmogenic 10Be and Low‐Temperature Thermochronology

“…The Tian Shan has interacted with the westerlies since the late Oligocene (X. Wang et al., 2020). In the mid‐Pliocene and during Quaternary interglacial periods, northerly migration of the westerlies induced higher precipitation, whereas their southward migration during Quaternary glacial periods led to drier climate conditions (Botsyun et al., 2022).…”