Water Isotope Records of Past Climate: Insights from a Greenland Ice Core and a Japanese Stalagmite

Abstract

Oxygen and hydrogen isotopes of water preserved in natural archives are fundamental proxies for reconstructing past climate. This study presents two examples. First, the Greenland core, obtained by a Japanese team, was dated by aligning oxygen isotope data with an isotope-enabled climate model, resulting in a near-monthly age scale. High snow accumulation preserved sub-seasonal signals, providing a basis for investigating atmospheric processes, such as the transport and deposition of volcanic aerosols. Second, isotopic measurements of fluid inclusions (liquid water trapped within the calcite of stalagmites) were used to examine mid-Holocene hydroclimate responses to volcanic forcing. A speleothem from Okinawa, Japan, recorded cooling or sustained cooling phases during periods of clustered volcanic eruptions, suggesting that such events likely contributed to multi-decadal variability. These examples demonstrate how traditional water isotope data, when integrated with advanced analytical techniques and climate model outputs, can unlock previously inaccessible insights into the mechanisms of climate forcing.