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Sketch illustrating the relationship between obliquity, Southern Hemisphere subtropical front (STF), Agulhas leakage (AL), Atlantic meridional overturning circulation (AMOC), North Atlantic sea ice cover (SI) and Intertropical Convergence Zone (ITCZ). (a) High obliquity phase: the poleward shift of the STF causes increased AL, accompanied by strengthening of the AMOC that leads to contracted SI, further inducing the northward migration of the ITCZ; (b) Low obliquity phase: the equatorward shift of the STF causes decreased AL, accompanied by AMOC weakening that leads to expanded SI, further inducing the southward migration of the ITCZ. Symbols refer to the different proxy records used in this study. Golden star marks Core U1483 (this study). Colored filled circles mark Jingyuan Loess Section (Sun et al., 2019), Xifeng Loess Section (Li et al., 2017), Core MD96‐2080 (Mejía et al., 2014), Core MD96‐2081 (Peeters et al., 2004), Core 1063 (Böhm et al., 2015) and Core 929 (Howe & Piotrowski, 2017), respectively. Positions of the ITCZ in high and low obliquity references to modern positions of the ITCZ in July and January (Lutgens & Tarbuck, 2001). AC: Agulhas Current.
Source publication
Obliquity influences the latitudinal position of the Intertropical Convergence Zone (ITCZ). However, the specific forcing mechanism remains unclear due to scarcity of long‐term and high‐resolution precipitation records from the Indo‐Pacific region. Here, we present a new, extended, high‐resolution (∼2 kyr) precipitation record covering the past ∼41...
Citations
... First, there is controversy over which orbital parameter dominates climate change in the region. While most records exhibit obvious precessional cycles (Carolin et al., 2013;Carolin et al., 2016;Dang et al., 2015;Hollstein et al., 2020;Tachikawa et al., 2011;Wu et al., 2012), some records show significant glacialinterglacial cycles (Pico et al., 2020;Windler et al., 2021;Windler et al., 2019) and/or obliquity cycles Zhang et al., 2022;Zhang et al., 2020b). Second, the mechanism underlying these changes is controversial. ...
... only migrate to a relatively warmer hemisphere but also can contract/expand in the latitudinal range to modulate monsoonal rainfall changes on orbital-to millennial-scales (e.g., Broccoli et al., 2006;Chiang & Bitz, 2005;Sachs et al., 2009;Schmidt & Spero, 2011;Yan et al., 2015;Zhang et al., 2022). However, less is known about the long-term evolution of the ITCZ mean position and intensity, and its relation to the meridional SST gradient in the Quaternary. ...
Plain Language Summary
The Hadley circulation and westerlies have been revealed to strengthen and shift equatorward across the mid‐Pleistocene transition (MPT), yet how the ITCZ, the uplifting branches of the Hadley Circulation, changed remains elusive. As precipitation is a key indicator of the ITCZ, here we use the residual oxygen isotope (δ¹⁸O) of calcite, calculated from planktic foraminiferal δ¹⁸O and Mg/Ca, to reconstruct the sea surface salinity (SSS) change and track precipitation change in the central equatorial Pacific during the past ∼1,780 kyr. In contrast to the stable SSS condition in the far western part of the Western Pacific, our new SSS record shows a striking secular decreasing trend across the MPT and represents a hydrological transition from evaporation‐control to precipitation‐control state. We suggest that the long‐term hydrological reorganization was the result of the gradual southward migration and intensification of the North Pacific ITCZ across the MPT, which was closely related to the increased meridional sea surface temperature gradients and the enhancements of trade winds.
... Obliquity controls the seasonal distribution of solar radiation: when obliquity is high, the subsolar point in boreal summer moves farther north and middle-high latitude areas receive more insolation; when obliquity is low, the subsolar point in boreal summer makes limited movement northward (Hinnov, 2018). Studies show that the longitudinal migration of the Intertropical Convergence Zone (ITCZ) is also paced by obliquity (Liu et al., 2015;Zhang et al., 2022b). ITCZ and the subtropical high north of ITCZ migrate farther north in boreal summer during high obliquity period. ...
Middle Eocene saw several global warming events. However, the terrestrial climate linkage to the warming events is still enigmatic. Particularly, the paleoclimate of middle Eocene East Asia is unclear when the East Asian monsoons started to prevail. Here, we present a combination of high-resolution elemental, compositional and natural gamma-ray (GR) records and conduct an orbital-scale paleoclimate reconstruction for the middle Eocene lacustrine shale dated from 43.4 to 40.9 Ma in the Bohai Bay Basin, East Asia. The results show an obvious shift in orbital variability from obliquity- to eccentricity-dominated cycles and an evident humidification at ~41.9 Ma in the East Asia. Eccentricity maxima filtered from the terrestrial records coincide with the deep-sea temperature rises during ~41.9-41.5 Ma. The terrestrial climate transition at 41.9 Ma was most likely attributed to intensification of the East Asian monsoons responding to the elevated atmospheric pCO2 during the concurrent global warming.
Airborne mineral dust is sensitive to climatic changes, but its response to orbital forcing is still not fully understood. Here, we present a reconstruction of dust input to the Subarctic Pacific Ocean covering the past 190 kyr. The dust composition record is indicative of source moisture conditions, which were dominated by precessional variations. In contrast, the dust flux record is dominated by obliquity variations and displays an out‐of‐phase relationship with a dust record from the mid‐latitude North Pacific Ocean. Climate model simulations suggest precession likely drove changes in the aridity and extent of dust source regions. Additionally, the obliquity variations in dust flux can be explained by meridional shifts in the North Pacific westerly jet, driven by changes in the meridional atmospheric temperature gradient. Overall, our findings suggest that North Pacific dust input was primarily modulated by orbital‐controlled source aridity and the strength and position of the westerly winds.
