A low-latitude framework for climate variability over the last 60,000 years

Climate variability during the last 60,000 years exhibited pronounced fluctuations on glacial-interglacial to sub-orbital timescales, yet fundamental questions remain regarding the timing, phasing, and cyclical structure of global climate fluctuations. Here we present ASM-2026, a composite of multiple high-resolution speleothem oxygen isotope (δ¹⁸O) records from the Asian summer monsoon (ASM) domain spanning the last 60 ka. Anchored by a rigorously constrained U-Th chronology (XJTU-1.0), this record resolves monsoon variability at multidecadal to millennial scales and provides robust geochronological benchmarks for correlating inter-regional climate variability. Our analysis indicates that ASM dynamic variability is only weakly linked to high-latitude ice-sheet forcing in either hemisphere, but closely tracks changes in the Atlantic Meridional Overturning Circulation (AMOC). Terminations of Heinrich Stadials are consistently preceded by centennial-scale weakening of the South American monsoon, likely associated with a shift in the Antarctic Oscillation from positive to negative phase, implicating a low-latitude and/or Southern Hemisphere trigger for abrupt climate reorganization. The record contains pronounced ~4.5-ka cycle close to one-quarter of the precession period, consistent with the modulation by the equatorial insolation forcing. At multidecadal to centennial timescales, the amplitude and periodicity of variability in the ASM and Greenland climate records diminish from glacial to interglacial conditions, whereas Antarctic variability displays an opposing response, highlighting a fundamental reorganization of teleconnections and forcing pathways across climate states.