Persistent Link Between Caribbean Precipitation and Atlantic Ocean Circulation During the Last Glacial Revealed by a Speleothem Record From Puerto Rico

Abstract

The sensitivity of tropical Atlantic precipitation patterns to the mean position of the Intertropical Convergence Zone (ITCZ) at different time scales is well-known. However, recent research suggests a more complex behavior of the northern hemispheric tropical rain belt related to the ITCZ in the western tropical Atlantic. Here we present a precisely dated speleothem multi-proxy record from a well-monitored cave in Puerto Rico, covering the period between 46.2 and 15.3 ka. The stable isotope and trace element records document a pronounced response of regional rainfall to abrupt climatic excursions in the North Atlantic across the Last Glacial such as Heinrich stadials and Dansgaard/Oeschger events. The annual to multidecadal resolution of the proxy time series allows substructural investigations of the recorded events. Spectral analysis suggests that multidecadal to centennial variability persisted in the regional hydroclimate mainly during interstadial conditions but also during the Last Glacial Maximum. In particular, we observe a strong agreement between the speleothem proxy data and the strength of the Atlantic meridional overturning circulation, supporting a persistent link of oceanic forcing to regional precipitation. Comparison to other paleo-precipitation records enables the reconstruction of past changes in position, strength, and extent of the ITCZ in the western tropical Atlantic in response to millennial-and orbital-scale global climate change. Plain Language Summary It is important to understand the climatic circumstances of how rainfall in the western tropical Atlantic varies under a changing climate to better manage the water supply for millions of people. However, it is not well understood how rainfall varied in the past, especially during the Last Glacial period, a time of strong climate variability and abrupt climate changes. Here, we use a stalagmite from Puerto Rico to create a new record of past changes in rainfall in this region. For this purpose, we analyzed proxy data that reveal a series of wet and dry periods during the Last Glacial corresponding to rapid global climate shifts. Our rainfall-sensitive stalagmite record captured changes of the tropical rain belt on various timescales and shows that this variability in rainfall is closely connected to changes in the strength of the ocean circulation. This suggests that the link between the ocean and the atmosphere is more robust than previously assumed. The comparison of our record with other rainfall-sensitive records from Central America and the northern Caribbean allows for a detailed reconstruction of the spatial and temporal changes of the western tropical Atlantic rain belt.

Coupled atmosphere-ice-ocean dynamics during Heinrich Stadial 2

“… a NGRIP deuterium-excess record 69 on the GICC05 chronology and shifted by +320 years. b – g speleothem δ 18 O records from Yongxing Cave (YX-51, this study), Cherrapunji Cave (Cherrapunji, this study), Larga Cave (PA-LA-1 96 ), Marota Cave (MAG, this study), Paixão Cave (PX-07, this study), and Botuverá Cave (BTV-4C, this study), respectively. h Antarctica 5-core averaged d ln anomaly 16 .…”

Late Quaternary Abrupt Climate Change in the Tropics and Sub‐Tropics: The Continental Signal of Tropical Hydroclimatic Events (THEs)

“…A speleothem record from Cuba, spanning the last ∼96 ka, also suggests that generally cooler and drier conditions prevailed during HEs, as recorded by a reduction in growth rates and a slight enrichment in oxygen isotopes (Warken et al., 2019). This conclusion is reinforced by trace element and δ 18 O in a stalagmite from Larga Cave, Puerto Rico, which registered consistently dry conditions during the time of HEs 1–4 (Warken et al., 2020; Figure 6).…”

“… Oxygen isotope record from stalagmites in Santo Tomas Cave, Cuba (black) and Cueva Larga, Puerto Rico (red; Warken et al., 2019, 2020). Dashed blue lines indicate the timing of maximum IRD in the stacked record of 15 North Atlantic cores (from Lisiecki & Stern, 2016).…”

The impact of seasonal and event‐based infiltration on transition metals (Cu, Ni, Co) in tropical cave drip water

“…Analyses of the common conservative proxies such as Mg/Ca or δ 18 O values in Larga Cave drip waters and speleothems reveal that they trace interannual to multidecadal precipitation changes due to large reservoir effects 14,40,68 . In contrast, transition metal ratios in drip waters from this cave respond to seasonal but also interannual and even event‐based infiltration, with residence times of a few weeks to months (Section 4.2).…”