Rainfall variations in central Indo-Pacific over the past 2,700 y

Abstract

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.

Meridional ITCZ shifts modulate tropical/subtropical Asian monsoon rainfall

“…Such meridional movements of the ITCZ could have led to changes in precipitation trend, e.g., relatively drier MWP and CWP but wetter LIA and DACP hydroclimatic conditions. The hydroclimatic patterns identified by Tan et al [9] also support our previous findings [5]. As shown in Fig.…”

“…1). Whereas Tan et al [9] provide us a new point that the meridional ITCZ shift could also have potentially influenced the tropical/subtropical MWP and LIA monsoon precipitation.…”

“…Recently, Tan et al [9], for the first time, developed a 2000-a long ITCZ shifting index in the central Indo-Pacific region, based on stalagmite d 18 O differences (D 18 O) between well-dated stalagmites in the Klang Cave (southern Thailand) and those in Indonesia. The most notable feature in Tan et al's ITCZ shifting index is that the north-south movement of the ITCZ, on centennial scale, is broadly synchronous with the north-south hemisphere temperature gradient [9,10], which further supports the point that the north-south hemisphere temperature gradient leads to the shifts of the atmospheric circulation, affecting water vapor and heat transfer, and subsequently modulating regional hydroclimatic changes. This is therefore an important contribution to the understanding of hydroclimatic changes, regional differences, and the dynamics in tropical/subtropical Asian monsoon areas.…”

“…The D 18 O-based ITCZ shifting index by Tan et al [9] shows an overall southward movement trend over the past two millennia, a southward displacement during the early Medieval Warm Period (MWP;~950-1150 CE) and the Current Warm Period (CWP), and a relative northward displacement during the Little Ice Age (LIA) and Dark Ages Cold Period (DACP). Such meridional movements of the ITCZ could have led to changes in precipitation trend, e.g., relatively drier MWP and CWP but wetter LIA and DACP hydroclimatic conditions.…”

Multi‐Centennial‐Scale Variations of South American Summer Monsoon Intensity in the Southern Central Andes (24–27°S) During the Late Holocene

“…Whereas we observe drier conditions (reduced SASM) and a negative SOI‐phase (El Niño‐like) for the Medieval Climate Anomaly, common interpretations associate the Medieval Climate Anomaly with La Niña‐like conditions, while the LIA is often associated with El Niño‐like conditions (e.g., Cobb et al, ; Denniston et al, ; Mann et al, ). However, interpretations are still subject to scientific discussions, and even contrary results have been published (Conroy et al, ; Lüning et al, ; Moy et al, ; Martel‐Cea et al, ; Rustic et al, ; Tan et al, ; Yan et al, ; see Figure S3). Barr et al () stated that differences in interpretation arise due to heterogenic relationship between terrestrial hydroclimate proxies, oceanic sea surface temperature proxies, and theoretical and physical models of predicted responses to global temperature changes.…”