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Abstract The Malagasy Summer Monsoon is an important part of the larger Indian Ocean and tropical monsoon region. As the effects of global warming play out, changes to precipitation in Madagascar will have important ramifications for the Malagasy people. To help understand how precipitation responds to climate changes we present a long-term Holocene speleothem record from Anjohibe, part of the Andranoboka cave system in northwestern Madagascar. To date, it is the most complete Holocene record from this region and sheds light on the nature of millennial and centennial precipitation changes in this region. We find that over the Holocene, precipitation in northwestern Madagascar is actually in phase with the Northern Hemisphere Asian monsoon on multi-millennial scales, but that during some shorter centennial-scale events such as the 8.2 ka event, Anjohibe exhibits an antiphase precipitation signal to the Northern Hemisphere. The ultimate driver of precipitation changes across the Holocene does not appear to be the meridional migration of the monsoon. Instead, zonal sea surface temperature gradients in the Indian Ocean seem to play a primary role in precipitation changes in northwestern Madagascar. 

We present a continuous high-resolution precisely dated multiproxy record of hydroclimate variability at Anjohibe cave in northwestern Madagascar using speleothem AB13. The record spans from ~4484 y BP to ~2863 y BP. Stalagmite δ¹⁸O, δ¹³C and Sr/Ca ratios show very similar changes in hydroclimate. The mechanism controlling Sr/Ca changes, however, from prior calcite precipitation to degree of dolomite dissolution at about 4 ky BP. Our record is also in good agreement with previously published speleothem records from the same area. This agreement and multiproxy consensus indicate that AB13 provides a robust record of hydroclimate variability, including a continuous record of hydroclimate variability across the 4.2 ka event. This 4.2 ka event in Madagascar is marked by two distinct periods of drying between ~3900 y BP to 4300 y BP. A dry 4.2 ka event at this Southern Hemisphere site helps limit possible mechanisms for the event, indicating that a meridional shift to the south in the ITCZ is not responsible for the 4.2 ka event. In addition, the 4.2 ka event does not stand out as a unique dry period in our record. The longest and driest period of the record lasted ~300 years with peak dryness at ~3000 y BP. Our record differs significantly from a speleothem record from Rodrigues Island, located ~1800 km to the east of our study area in Madagascar suggesting different climatological controls on northwest Madagascar and more oceanic sites to the east. 

High-resolution records from past interglacial climates help constrain future responses to global warming, yet are rare. This dataset contains seasonally-resolved climate records from subarctic-Canada using micron-scale measurements of oxygen isotopes (δ18O) in speleothems with apparent annual growth bands from three interglacial periods – Marine Isotope Stages 11 (409-376 ka), 9 (336-305 ka) and MIS 5e (123-118 ka). Our study highlights the potential for high-latitude speleothems to yield detailed isotopic records of Northern Hemisphere interglacial climates beyond the reach of Greenland ice cores and offers a framework for interpreting them. Table S1 contains the Uranium-Thorium dates for six speleothems, or more specifically, flowstones, from a cave in Northwest Territories (NWT), Canada. It also contains constructed age models for each sample. Then, we applied a two-tiered methodological approach to reconstruct past subarctic climate. First, we produce an ultra-high-resolution δ18O record that, although not continuous, spans thousands of years for portions of these interglacials. This record was created using Secondary Ion Mass Spectrometry (SIMS) to measure δ18O approximately every 35-micrometer (µm) down each sample’s growth axis. This data is shown in Table S2. Second, we used Confocal Laser Fluorescence Microscopy (CLFM) to identify several fluorescent annual bands in each speleothem, which we then targeted for additional SIMS measurements. This data is shown in Table S3. Though these subarctic speleothems are small in size (most are less than 10 centimeter (cm) in length), the application of both CLFM and SIMS on these samples demonstrate their potential for providing ultra-high-resolution records of high-latitude Northern Hemisphere terrestrial climate outside of Greenland and provide insights into interpretive frameworks for future cold-region speleothem δ18O records. 

Abstract We reconstructed hydroclimate variability in the Yucatán Peninsula (YP) based on stalagmite oxygen and carbon isotope records from a well-studied cave system located in the northeastern YP, a region strongly influenced by Caribbean climate dynamics. The new stalagmite isotopic records span the time interval between 43 and 26.6 ka BP, extending a previously published record from the same cave system covering the interval between 26.5 and 23.2 ka BP. Stalagmite stable isotope records show dominant decadal and multidecadal variability, and weaker variability on millennial timescales. These records suggest significant precipitation declines in the broader Caribbean region during Heinrich events 4 and 3 of ice-rafted discharge into the North Atlantic, in agreement with the antiphase pattern of precipitation variability across the equator suggested by previous studies. On millennial timescales, the stalagmite isotope records do not show the distinctive saw-tooth pattern of climate variability observed in Greenland during Dansgaard–Oeschger (DO) events, but a pattern similar to North Atlantic sea surface temperature (SST) variability. We propose that shifts in the mean position of the Intertropical Convergence Zone (ITCZ), per se, are not the dominant driver of last glacial hydroclimate variability in the YP on millennial timescales but instead that North Atlantic SSTs played a dominant role. Our results support a negative climate feedback mechanism whereby large low latitude precipitation deficits resulting from AMOC slowdown would lead to elevated salinity in the Caribbean and ultimately help reactivate AMOC and Caribbean precipitation. However, because of the unique drivers of future climate in the region, predicted twenty-first century YP precipitation reductions are unlikely to be modulated by this negative feedback mechanism.