Tropical rainfall variability is closely linked to meridional shifts of the Intertropical Convergence Zone (ITCZ) and zonal movements of the Walker circulation. The characteristics and mechanisms of tropical rainfall variations on centennial to decadal scales are, however, still unclear. Here, we reconstruct a replicated stalagmite-based 2,700-y-long, continuous record of rainfall for the deeply convective northern central Indo-Pacific (NCIP) region. Our record reveals decreasing rainfall in the NCIP over the past 2,700 y, similar to other records from the northern tropics. Notable centennial- to decadal-scale dry climate episodes occurred in both the NCIP and the southern central Indo-Pacific (SCIP) during the 20th century [Current Warm Period (CWP)] and the Medieval Warm Period (MWP), resembling enhanced El Niño-like conditions. Further, we developed a 2,000-y-long ITCZ shift index record that supports an overall southward ITCZ shift in the central Indo-Pacific and indicates southward mean ITCZ positions during the early MWP and the CWP. As a result, the drying trend since the 20th century in the northern tropics is similar to that observed during the past warm period, suggesting that a possible anthropogenic forcing of rainfall remains indistinguishable from natural variability.
|Original language||English (US)|
|Number of pages||6|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - Aug 27 2019|
Bibliographical noteFunding Information:
ACKNOWLEDGMENTS. We gratefully acknowledge the grants from National Key Research and Development Program of China (2017YFA0603401 to L.T. and Y.C.), Shaanxi Science Fund for Distinguished Young Scholars (2018JC-023 to L.T.), and Youth Innovation Promotion Association of Chinese Academy of Sciences (2012295 to L.T.). This study was mainly supported by the Science Vanguard Research Program of the Ministry of Science and Technology (107-2119-M-002-051 to C.-C.S.), the National Taiwan University (105R7625 to C.-C.S.), and the Higher Education Sprout Project of the Ministry of Education (107L901001 and 108L901001 to C.-C.S.). This study was partially supported by grants from Swedish Research Council (621-2008-2855, 348-2008-6071, and 621-2011-4684 to B.W.); NSF (NSF 1702816, EAR-0908792, and EAR-1211299 to R.L.E. and H.C.); Thailand Research Fund
(MRG5980080 to S.C.) and Development and Promotion of Science and Technology Talents Project (042/2558 to S.C.); and European Union’s Horizon 2020 Research and Innovation Programme under the Marie Skłodowska-Curie Grant Agreement (691037 to S.F.M.B.).
- Central Indo-Pacific