Abstract
The evolutionary dynamics of El Niño Southern Oscillation (ENSO) over the last glacial period remains understudied, despite its potential in providing a “cold case” for climate sensitivity studies. Here, we investigate SE Asian-Pacific paleoclimate records to decipher the dominant underlying mechanism that governed tropical Asian-Pacific hydrology during MIS 3. Our results suggest that the glacial emergence of the Sunda Shelf likely altered the atmospheric circulation pattern in Southeast (SE) Asia and led to the realignment of rainfall patterns between Thailand and Indonesia during the last glacial period. We also propose that the long-term hydrological regime change in the tropical Asian-Pacific region during MIS 3 was mainly influenced by an El Niño-like mechanism. An intense El Niño-like condition led to strong aridity in SE Asia during mid MIS 3. By late MIS 3, an enhanced seasonality dampened the intensity of the El Niño-like conditions, thus, leading to muted aridity in SE Asia. The alternating warm and wet summer months and droughts during winter favoured the proliferation of C4 plant types in Northern Thailand from mid MIS 3 to late MIS 3.
Highlights
Marine Isotope Stage 3 (MIS-3), a period that spans approximately 60 ka B.P. to 26 ka BP, was characterised by abrupt shifts between warm and cold climate states, the so-called Dansgaard–Oeschger (D-O) events (Dansgaard et al, 1993)
We propose that the long-term hydrological regime change in the tropical Asian-Pacific region during MIS-3 was mainly influenced by an El-Nino-like mechanism whose intensity fluctuated with global atmospheric CO2 concentrations
Since the Sunda Shelf was sub-aerially exposed to its maximum extent by mid-MIS-3 (~43 ka BP) (Bird et al, 2005), we suggest that the mean climatic state that governed the tropical Asian-Pacific during mid- to lateMIS-3 was largely modulated by El Niño
Summary
Marine Isotope Stage 3 (MIS-3), a period that spans approximately 60 ka B.P. to 26 ka BP, was characterised by abrupt shifts between warm and cold climate states, the so-called Dansgaard–Oeschger (D-O) events (Dansgaard et al, 1993). Related to some of the colder D-O events are six distinctive periods known as Heinrich (H) events (Heinrich, 1988) These millennial-scale events are both prominent in Greenland (Dansgaard et al, 1993; Johnsen et al, 1992) and Antarctic ice core records (Barbante et al, 2006) but offset in the latter (Veres et al, 2013), which has led to the concept of a bipolar seesaw between the Northern and Southern Hemispheres (see Landais et al, 2015). Conditions were normalised, allowing heat transport to drive ice melt in the Northern Hemisphere and a return to warmer conditions
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