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Abstract Describing the processes that regulate the flows and exchanges of water within the atmosphere and between the atmosphere and Earth’s surface is critical for understanding environmental change and predicting Earth’s future accurately. The heavy-to-light hydrogen and oxygen isotope ratios of water provide a useful lens through which to evaluate these processes due to their innate sensitivity to evaporation, condensation, and mixing. In this review, we examine how isotopic information advances our understanding about the origin and transport history of moisture in the atmosphere and about convective processes—including cloud mixing and detrainment, precipitation formation, and rain evaporation. Moreover, we discuss how isotopic data can be used to benchmark numerical simulations across a range of scales and improve predictive skill through data assimilation techniques. This synthesis of work illustrates that, when paired with air mass thermodynamic properties that are commonly measured and modeled (such as specific humidity and temperature), water’s isotope ratios help shed light on moist processes that help set the climate state. 

Abstract Stable isotopes of oxygen (δ¹⁸O) in seawater reflect the combined influences of ocean circulation and atmospheric moisture balance. However, it is difficult to disentangle disparate ocean and atmosphere influences on modern seawater δ¹⁸O values, partly because continuous time series of seawater δ¹⁸O are rare. Here we present a nearly nine‐year, continuous record of seawater δ¹⁸O values from the Galápagos. Seawater δ¹⁸O values faithfully track sea surface salinity and salinity along the equator at 50 m depth. Zonal current velocity within the Equatorial Undercurrent (EUC), directly west of the Galápagos, is strongly correlated with Galápagos surface seawater δ¹⁸O values with a 1‐month lag. Reconstructions of Galápagos seawater δ¹⁸O values could thus provide a window into past variations in the strength of the EUC, an important influence on large‐scale tropical Pacific climate. 

ABSTRACT The Rocks loess section, in unglaciated western Kentucky, provides a high‐resolution environmental record during the last glacial maximum onset. The Peoria Silt (9 m thick) contains 26 terrestrial gastropod species, with up to 15 species within a single 5 cm interval. Thirteen radiocarbon ages, using shells or charcoal, range between 30 and 24.5 cal ka; younger loess has been leached or eroded. Stratigraphic shifts in gastropod assemblages imply significant cooling, particularly ~27 cal ka, as solar insolation was decreasing and the southern Laurentide Ice Sheet rapidly advancing. Midwestern to southern species (e.g.Anguispira kochi,Gastrocopta pentodon,Hawaii miniscula,Helicodiscus parallelus,Vallonia perspectiva) occur only in the lowermost Peoria Silt (~30–27 cal ka). In contrast, cold‐tolerant species (Columella alticola,Vertigo modesta, Vallonia gracilicosta)occur only in full glacial Peoria Silt (27–24.5 cal ka). Inferred mean July temperatures, from mutual climatic range methods, range from ~23 °C at 30 cal ka, cooling to ~18 °C by 26 cal ka; about 3–8 °C cooler than today (~26 °C). Superimposed on this cooling trend are multi‐centennial variations in detrital carbonate, fossil shell concentrations, palaeotemperature estimates, and oxygen isotope values (Vertigo,Discus, Helicodiscus). The finer‐scale variations imply relatively synchronous fluctuations in glacial sediment supply, loess sedimentation, and climate.