Expansion and Contraction of the Indo-Pacific Tropical Rain Belt over the Last Three Millennia

Abstract

The seasonal north-south migration of the intertropical convergence zone (ITCZ) defines the tropical rain belt (TRB), a region of enormous terrestrial and marine biodiversity and home to 40% of people on Earth. The TRB is dynamic and has been shown to shift south as a coherent system during periods of Northern Hemisphere cooling. However, recent studies of Indo-Pacific hydroclimate suggest that during the Little Ice Age (LIA; AD 1400–1850), the TRB in this region contracted rather than being displaced uniformly southward. This behaviour is not well understood, particularly during climatic fluctuations less pronounced than those of the LIA, the largest centennial-scale cool period of the last millennium. Here we show that the Indo-Pacific TRB expanded and contracted numerous times over multi-decadal to centennial scales during the last 3,000 yr. By integrating precisely-dated stalagmite records of tropical hydroclimate from southern China with a newly enhanced stalagmite time series from northern Australia, our study reveals a previously unidentified coherence between the austral and boreal summer monsoon. State-of-the-art climate model simulations of the last millennium suggest these are linked to changes in the structure of the regional manifestation of the atmosphere’s meridional circulation.

Speleothem Paleoclimatology for the Caribbean, Central America, and North America

“…A number of precipitation-based records suggest that the seasonal extremes of the ITCZ rainbelt respond to local summer insolation, and consequently the rainbelt seasonal range undergoes latitudinal migrations [10,[132][133][134][135][136]. Other evidence suggests that the ITCZ rainbelt contracted/expanded around its mean position [120,[137][138][139]. According to this argument, asymmetric extratropical forcings like ice sheets or freshwater hosing produce meridional shifts in the zonal mean rainbelt, but orbital variations produce expansion/contractions in terms of the global zonal mean [120].…”

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

“…A – Stalagmites HY1 and HY2 from Huangye cave, China51; B – Stalagmite WX42B from Wanxiang cave, China52; C – Stalagmite DY1 from Dayu Cave, China53; D – Stalagmites SAH-A and SAH-B from Sahiya Cave, India54; E – Stalagmite A1 from Lianhua Cave, China55; F – Stalagmite YOK-I from Yok Balum cave, Belize8; G – Tree ring reconstruction from Bidoup Nui Ba National Park, Vietnam56; H – Sediment record from Bosumtwi Lake, Ghana57; I – Stalagmite CAS-D from Cascayunga cave, Peru58; J – Stalagmites 10FC-02 and 05FC-04 from Forestry Cave, Guadalcanal, Solomon Islands23; K – Stalagmites P00-H1 and P09-H2 from Huagapo cave, Peru59; L – Ice core from the Quelccaya ice cap, Peru60; M – Stalagmites from Curupira and Pau d’Alho Caves, Brazil61; N – Stalagmite CH-1 from Chillagoe, Australia62; O – Stalagmites KNI-51 F, G, I, O, P, and 11 from KNI-51 Cave, Australia63; P –Stalagmite DP1 from Dante cave, Namibia2122; Q – Stalagmite SU-96-7 from Uamh-an-Tartair cave, Scotland11. Winter wind vectors in the background are derived from 1950–2000 reanalysis data provided by the 20 th Century Reanalysis Composites from the NOAA Earth System Research Laboratory, Physical Science Division.…”

Wave-driven geomorphology of Pacific carbonate coastlines: from landscape to wavelength scale

“…However, the lack of inter-model agreement in the equatorial region for GPI and its individual components suggests that the anomalies there may not be a robust response to consistent forcing. South China Sea (Yu et al, 2009), Jaluit Atoll (this study), Tahaa, French Polynesia (Toomey et al, 2013(Toomey et al, , 2016b, and cave KNI-51, northwestern Australia (Denniston et al, 2015(Denniston et al, , 2016.…”

“…that then lasted to c. 1750 CE (Fig. 5-4e, Denniston et al, 2016). Simultaneously, multiple precipitation proxies in the deep tropical IPWP and South China Sea indicate the rapid onset of wetter climate (Yan et al, 2011(Yan et al, , 2015a.…”

“…Simultaneously, multiple precipitation proxies in the deep tropical IPWP and South China Sea indicate the rapid onset of wetter climate (Yan et al, 2011(Yan et al, , 2015a. These shifts have been attributed to a contraction of the Intertropical Convergence Zone (ITCZ) (Yan et al, 2015a;Denniston et al, 2016) (Fig. 2e), and a westward shift in the Pacific Walker Circulation (PWC) (Yan et al, 2011).…”