Mid-to-Late Holocene Hydroclimate in the Southwest USA: Evidence from Lava Tube Ice



The southwestern United States has historically faced droughts and tough climate conditions, a situation predating the extensive effects of human-caused climate change. In Dr. Onac’s research, he focused on reconstructing the hydroclimate patterns of the Mid-to-Late Holocene period by analyzing the δ18O of perennial ice found in lava tubes located in the El Malpais National Monument, New Mexico. They recovered three ice cores (95 to 110 cm in length) from which subsamples were cut or drilled at 1-cm intervals. They, then, measured the δ18O isotopic composition of ice-melted water samples. Ice chronology relies on 14C-dated charcoal fragments and organic-rich layers, and U/Th dating of ice-melt water. From their observations and research, Dr. Onac inferred that future climatic conditions in the southwest could lean towards aridity, especially if dominated by La Niña-like dry winters, potentially intensified by the negative phase of the Pacific Decadal Oscillation (PDO).

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