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1. Scientific drilling of Lake Chalco, Basin of Mexico (MexiDrill)

   https://doi.org/10.5194/sd-26-1-2019  

   Brown, Erik T.; Caballero, Margarita; Cabral Cano, Enrique; Fawcett, Peter J.; Lozano-García, Socorro; Ortega, Beatriz; Pérez, Liseth; Schwalb, Antje; Smith, Victoria; Steinman, Byron A.; et al (January 2019, Scientific Drilling)

   Abstract. The primary scientific objective of MexiDrill, the Basin of MexicoDrilling Program, is development of a continuous, high-resolution∼400 kyr lacustrine record of tropical North Americanenvironmental change. The field location, in the densely populated,water-stressed Mexico City region gives this record particular societalrelevance. A detailed paleoclimate reconstruction from central Mexico willenhance our understanding of long-term natural climate variability in theNorth American tropics and its relationship with changes at higher latitudes.The site lies at the northern margin of the Intertropical Convergence Zone(ITCZ), where modern precipitation amounts are influenced by sea surfacetemperatures in the Pacific and Atlantic basins. During the Last GlacialMaximum (LGM), more winter precipitation at the site is hypothesized to have beena consequence of a southward displacement of the mid-latitude westerlies. Itthus represents a key spatial node for understanding large-scalehydrological variability of tropical and subtropical North America and isat an altitude (2240 m a.s.l.), typical of much of western North America. In addition, its sediments contain a rich record of pre-Holocene volcanichistory; knowledge of the magnitude and frequency relationships of thearea's explosive volcanic eruptions will improve capacity for riskassessment of future activity. Explosive eruption deposits will also be usedto provide the backbone of a robust chronology necessary for fullexploitation of the paleoclimate record. Here we report initial resultsfrom, and outreach activities of, the 2016 coring campaign. 

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2. US Gulf Coast tropical cyclone precipitation influenced by volcanism and the North Atlantic subtropical high

   https://doi.org/10.1038/s43247-022-00494-7  

   Bregy, Joshua C.; Maxwell, Justin T.; Robeson, Scott M.; Harley, Grant L.; Elliott, Emily A.; Heeter, Karen J. (July 2022, Communications Earth & Environment)

   Abstract Understanding the response of tropical cyclone precipitation to ongoing climate change is essential to determine associated flood risk. However, instrumental records are short-term and fail to capture the full range of variability in seasonal totals of precipitation from tropical cyclones. Here we present a 473-year-long tree-ring proxy record comprised of longleaf pine from excavated coffins, a historical house, remnant stumps, and living trees in southern Mississippi, USA. We use cross-dating dendrochronological analyses calibrated with instrumental records to reconstruct tropical cyclone precipitation stretching back to 1540 CE. We compare this record to potential climatic controls of interannual and multidecadal tropical cyclone precipitation variability along the Gulf Coast. We find that tropical cyclone precipitation declined significantly in the two years following large Northern Hemisphere volcanic eruptions and is influenced by the behavior of the North Atlantic subtropical high-pressure system. Additionally, we suggest that tropical cyclone precipitation variability is significantly, albeit weakly, related to Atlantic multidecadal variability. Finally, we suggest that we need to establish a network for reconstructing precipitation from tropical cyclones in the Southeast USA if we want to capture regional tropical cyclone behavior and associated flood risks. 

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3. Pacific Interannual and Multidecadal Variability Recorded in δ ¹⁸ O of South American Summer Monsoon Precipitation

   https://doi.org/10.1029/2024JD040999  

   Orrison, R; Vuille, M; Rodrigues, J C; Stríkis, N M; Cruz, F; Rodriguez‐Caton, M; Andreu‐Hayles, L (September 2024, Journal of Geophysical Research: Atmospheres)

   Abstract The South American summer monsoon (SASM) generates important hydroclimatic impacts in (sub‐)tropical South America and isotopic tracers recorded in paleoclimatic archives allow for assessing its long‐term response to Pacific variability prior to modern observations. Stable oxygen isotopes in precipitation integrate hydroclimatic changes during the SASM mature phase from December to February (DJF) in response to the Interdecadal Pacific Oscillation (IPO) and El Niño—Southern Oscillation (ENSO), respectively. Here, results from the isotope‐enabled Community Atmosphere Model v.5 are compared with highly resolved and precisely dated isotopic records from speleothems, tree rings, lake and ice cores during the industrial era (1880–2000 CE) and validated against observations from the International Atomic Energy Agency (IAEA) network. Pacific sea surface temperatures (SSTs) are coupled to the isotopic composition of SASM precipitation through perturbations in the Walker circulation associated with low‐ (IPO) and high‐frequency (ENSO) variability, impacting convective activity over tropical South America and the tropical Atlantic. Changes in convection over this monsoon entrance region ultimately control the downstream oxygen isotopic composition of precipitation recorded in paleoclimate archives. Overall, model results, paleoclimate records and IAEA data agree on the isotopic response to Pacific SST forcing. These results highlight the potential for long isotopic paleoclimate records to reconstruct Pacific climate variability on both high‐ and low‐frequency timescales. Furthermore, the isolation of the IPO signal in a diverse set of isotopic archives invites the reinterpretation of other paleoclimate proxies for identifying this historically overlooked forcing. 

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4. ENSO’s Response to Volcanism in a Data Assimilation‐Based Paleoclimate Reconstruction Over the Common Era

   https://doi.org/10.1029/2021PA004290  

   Dee, Sylvia G.; Steiger, Nathan J. (March 2022, Paleoceanography and Paleoclimatology)

   Abstract The tropical response to explosive volcanism remains underconstrained in the paleoclimate record. While the atmosphere cools due to aerosol forcing following volcanic eruptions, modeling evidence suggests that the tropical Pacific responds with compensatory warming. Given the rarity of large volcanic eruptions and the short instrumental record, these modeling results require independent verification. Here, we test for links between volcanism and tropical Pacific dynamics using the newly developed Paleo Hydrodynamics Data Assimilation product (PHYDA), which spans the past 2,000 years. Using Pacific sea surface temperature fields from PHYDA and coincident volcanic eruptions, we test the response of the El Niño–Southern Oscillation (ENSO) to large, tropical volcanic eruptions. We identify a weak El Niño‐like response of the tropical Pacific in the year following sufficiently large, tropical volcanic eruptions. While the response is not significant at the 95% confidence level using superposed epoch analysis (SEA) and self‐organizing maps, a significant result does emerge when employing probability density functions. Our results indicate that the widely used SEA approach, based on composite averaging, may not be sufficiently sensitive to capture an ENSO response in the presence of large internal variability. We additionally conclude that inconsistencies in both the spatial patterns and magnitudes between climate models and PHYDA results indicate that current models overestimate the regional tropical response to volcanic forcing. 

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5. Global climate disruption and regional climate shelters after the Toba supereruption

   https://doi.org/10.1073/pnas.2013046118  

   Black, Benjamin A.; Lamarque, Jean-François; Marsh, Daniel R.; Schmidt, Anja; Bardeen, Charles G. (July 2021, Proceedings of the National Academy of Sciences)

   The Toba eruption ∼74,000 y ago was the largest volcanic eruption since the start of the Pleistocene and represents an important test case for understanding the effects of large explosive eruptions on climate and ecosystems. However, the magnitude and repercussions of climatic changes driven by the eruption are strongly debated. High-resolution paleoclimate and archaeological records from Africa find little evidence for the disruption of climate or human activity in the wake of the eruption in contrast with a controversial link with a bottleneck in human evolution and climate model simulations predicting strong volcanic cooling for up to a decade after a Toba-scale eruption. Here, we use a large ensemble of high-resolution Community Earth System Model (CESM1.3) simulations to reconcile climate model predictions with paleoclimate records, accounting for uncertainties in the magnitude of Toba sulfur emissions with high and low emission scenarios. We find a near-zero probability of annual mean surface temperature anomalies exceeding 4 °C in most of Africa in contrast with near 100% probabilities of cooling this severe in Asia and North America for the high sulfur emission case. The likelihood of strong decreases in precipitation is low in most of Africa. Therefore, even Toba sulfur release at the upper range of plausible estimates remains consistent with the muted response in Africa indicated by paleoclimate proxies. Our results provide a probabilistic view of the uneven patterns of volcanic climate disruption during a crucial interval in human evolution, with implications for understanding the range of environmental impacts from past and future supereruptions. 

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