Stalagmite multi-proxy evidence of wet and dry intervals in northeastern Namibia: Linkage to latitudinal shifts of the Inter-Tropical Convergence Zone and changing solar activity from AD 1400 to 1950

Abstract

Multiple proxies using variation in δ18O, δ13C, mineralogy, and petrography in a newly generated high-resolution record of Stalagmite DP1 from Dante Cave indicate a linkage between changes in hydroclimate in northeastern Namibia and changes in solar activity and changes in global temperatures. The record suggests that during solar minima and globally cooler conditions (ca. 1660–1710 and ca. 1790–1830), wetter periods (reflecting longer summer seasons) in northeastern Namibia were linked to advances of the Inter-Tropical Convergence Zone (ITCZ) and the Inter-Ocean Convergence Zone (IOCZ) southwestward. A slight southward push of the Angola–Benguela Front (ABF) during such intervals could also be expected, bringing more rainfall inland. On the other hand, drier and warmer periods in northeastern Namibia, inferred from the increasing δ18O trend in Stalagmite DP1 after AD 1715, coincide with globally warmer conditions, and thus a northeastward migration of the ITCZ, specifically with more warming of the Northern Hemisphere (NH). This finding agrees with reducing precipitation observed in the summer rainfall zone of southern Africa since ca. 1900. Therefore, predictions of warming in high-latitude regions of the NH in the next century should suggest that the presently semi-arid climate of northern Namibia may become even drier.

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.…”

“…The Yok Balum, Forestry, and Dante Cave records are directly influenced by the mean position of the ITCZ8212223 (with the Forestry Cave record being influenced primarily by the South Pacific Convergence Zone, the most persistent spur of the ITCZ2324). Monsoonal systems, like the ASM, the SASM, the Australian-Indonesian Summer Monsoon (AISM), the Indian Summer Monsoon (ISM), and the West African Monsoon (WAM) are affected by the hemispheric migration of the ITCZ as a major moisture flux conduit and by hemispheric temperature, because land-sea temperature contrasts drive the monsoonal systems1725.…”

Three distinct Holocene intervals of stalagmite deposition and nondeposition revealed in NW Madagascar, and their paleoclimate implications

“…This may indicate a more southerly mean position of the ITCZ. Factors that could influence the mean position of the ITCZ include changes in insolation (e.g., Haug et al, 2001;Wang et al, 2005;Cruz et al, 2005;Fleitmann et al, 2003Fleitmann et al, , 2007Schefuß et al, 2005;Suziki, 2011;Kutzbach and Liu, 1997;Partridge et al, 1997;Verschuren et al, 2009;Voarintsoa et al, 2017a) and difference in temperature between the two hemispheres (e.g., Chiang and Bitz, 2005;Broccoli et al, 2006;Chiang and Friedman, 2012;Kang et al, 2008;McGee et al, 2014;Talento and Barreiro, 2016). In contrast, the depositional hiatuses during the MMHI could suggest overall drier conditions, and thus a northward migration of the mean ITCZ.…”

“…The link between stalagmite growthnongrowth, cave drip water, and soil CO 2 is broadly influenced by changes in climate. Major hiatuses in stalagmite deposition could be marked by a variety of features, including the presence of erosional surfaces, chalkification, dirt bands and/or detrital layers, offsetting of the growth axis, and/or sometimes by color changes (e.g., Holmgren et al, 1995;Dutton et al, 2009;Railsback et al, 2013Voarintsoa et al, 2017a). Railsback et al (2013) were able to identify significant features in stalagmites that allow distinction between nondeposition during extremely wet conditions (Type E surfaces) and non- deposition during extremely dry conditions (Type L surfaces; Fig.…”

“…The correction consists of subtracting 0.8 ‰ for δ 18 O (Kim and O'Neil, 1997;Tarutani et al, 1969;Kim et al, 2007;Zhang et al, 2014) and 1.7 ‰ for δ 13 C (Rubinson and Clayton, 1969;Romanek et al, 1992) for the aragonite, as has been carried out previously (e.g., Holmgren et al, 2003;Sletten et al, 2013;Liang et al, 2015;Railsback et al, 2016;Voarintsoa et al, 2017a), as shown in Eqs. (2) and (3) below (where R A/C is the aragonite percentage if not 100 %).…”