See–saw relationship of the Holocene East Asian–Australian summer monsoon

Abstract

The East Asian-Indonesian-Australian summer monsoon (EAIASM) links the Earth's hemispheres and provides a heat source that drives global circulation. At seasonal and inter-seasonal timescales, the summer monsoon of one hemisphere is linked via outflows from the winter monsoon of the opposing hemisphere. Long-term phase relationships between the East Asian summer monsoon (EASM) and the Indonesian-Australian summer monsoon (IASM) are poorly understood, raising questions of long-term adjustments to future greenhouse-triggered climate change and whether these changes could 'lock in' possible IASM and EASM phase relationships in a region dependent on monsoonal rainfall. Here we show that a newly developed nonlinear time series analysis technique allows confident identification of strong versus weak monsoon phases at millennial to sub-centennial timescales. We find a see-saw relationship over the last 9,000 years-with strong and weak monsoons opposingly phased and triggered by solar variations. Our results provide insights into centennial-to millennial-scale relationships within the wider EAIASM regime.

Initial Expansion of C4 Vegetation in Australia During the Late Pliocene

“…Our record of C 4 expansion also coincides very closely with evidence of increased east Asian dust flux into marine sediments, at~3.5 Ma (Figure 3; Rea et al, 1993Rea et al, , 1998Snoeckx et al, 1995), widely interpreted as marking the initial intensification of the East Asian winter monsoon (EAWM) or Siberian High Guo et al, 2004;Rea et al, 1998;Sun et al, 1998;Zheng et al, 2004). The persistence of an east Asian-Australian precipitation teleconnection, in which northern cooling leads to southward migration of the Intertropical Convergence Zone, has been indicated at a range of Quaternary timescales from centennial-millennial (Denniston et al, 2013;Eroglu et al, 2016) to orbital (Y. Liu et al, 2003;Wyrwoll & Valdes, 2003), but are dominated by two opposed influences: within-hemisphere insolation forcing (Wyrwoll et al, 2007;Wyrwoll & Valdes, 2003), that is comparatively weak because of the relatively small, low relief land surface of northern Australia; and remote forcing driven by cross-equatorial thermal and pressure gradients between Australia and East Asia (An, 2000).…”

Tropical rainfall over the last two millennia: evidence for a low-latitude hydrologic seesaw

“…Monsoonal systems, like the ASM, the SASM, the Australian-Indonesian Summer Monsoon (AISM), the Indian Summer Monsoon (ISM), and the West African Monsoon (WAM) are affected by the hemispheric migration of the ITCZ as a major moisture flux conduit and by hemispheric temperature, because land-sea temperature contrasts drive the monsoonal systems1725. Although monsoonal variations might not necessarily be equivalent to ITCZ shifts, monsoons can be linked to ITCZ variations17262728. The SASM (Huagapo, Cascayunga, Curupira, and Pau d’Alho Caves, and Quelccaya Ice cap) and the AISM (Chillagoe Cave, KNI-51 Cave) records used here are all antiphased with respect to the NH records on decadal-centennial scales, indicating stronger SH monsoons when NH low latitudes are drier.…”

Multi-scale event synchronization analysis for unravelling climate processes: a wavelet-based approach

“…Synchronization is a widespread phenomenon that can be observed in numerous climate-related processes, such as synchronized climate changes in the northern and southern polar regions (Rial, 2012), see-saw relationships between monsoon systems (Eroglu et al, 2016), or coherent fluctuations in flood activity across regions (Schmocker-Fackel and Naef, 2010) and among El Niño and the Indian summer monsoon (Maraun and Kurths, 2005;Mokhov et al, 2011). Synchronous occurrences of climate-related events can be of great societal relevance.…”