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Billions of people rely upon groundwater for drinking water and agriculture, yet predicting how climate change may affect aquifer storage remains challenging. To gain insight beyond the short historical record, we reconstruct changes in groundwater levels in western North America during the last glacial termination (LGT, ~20 to 11 thousand years ago) using noble gas isotopes. Our reconstructions indicate remarkable stability of water table depth in a Pacific Northwest aquifer throughout the LGT despite increasing precipitation, closely matching independent Earth system model (ESM) simulations. In the American Southwest, ESM simulations and noble gas isotopes both suggest a pronounced LGT decline in water table depth in in response to decreasing precipitation, indicating distinct regional groundwater responses to climate. Despite the hydrologic simplicity of ESMs, their agreement with proxy reconstructions of past water table depth suggests that these models hold value in understanding groundwater dynamics and projecting large-scale aquifer responses to climate forcing. 

These data correspond to the article “Deep Nitrogen Fluxes and Sources Constrained by Arc Lava Phenocrysts” by Hudak et al. submitted to Geophysical Research Letters. Table S1 includes N-He-Ar data for FIs in phenocrysts from mafic are lavas and tephras. Table S2 contains the corrected N2/3He data used for volcanic arc N flux calculations and the arc-averaged mean N arc flux. Table S3 summarizes previous literature estimates of N fluxes and the data used for those calculations. Table S4 provides the N concentrations, He concentrations, N isotope compositions of the mantle, sediments, and altered oceanic crust, as well as sediment thicknesses. Finally, Table S5 gives information about the sources of the mineral separates used for these analyses. 

Gas exchange between the atmosphere and ocean interior profoundly impacts global climate and biogeochemistry. However, our understanding of the relevant physical processes remains limited by a scarcity of direct observations. Dissolved noble gases in the deep ocean are powerful tracers of physical air-sea interaction due to their chemical and biological inertness, yet their isotope ratios have remained underexplored. Here, we present high-precision noble gas isotope and elemental ratios from the deep North Atlantic (~32°N, 64°W) to evaluate gas exchange parameterizations using an ocean circulation model. The unprecedented precision of these data reveal deep-ocean undersaturation of heavy noble gases and isotopes resulting from cooling-driven air-to-sea gas transport associated with deep convection in the northern high latitudes. Our data also imply an underappreciated and large role for bubble-mediated gas exchange in the global air-sea transfer of sparingly soluble gases, including O 2 , N 2 , and SF 6 . Using noble gases to validate the physical representation of air-sea gas exchange in a model also provides a unique opportunity to distinguish physical from biogeochemical signals. As a case study, we compare dissolved N 2 /Ar measurements in the deep North Atlantic to physics-only model predictions, revealing excess N 2 from benthic denitrification in older deep waters (below 2.9 km). These data indicate that the rate of fixed N removal in the deep Northeastern Atlantic is at least three times higher than the global deep-ocean mean, suggesting tight coupling with organic carbon export and raising potential future implications for the marine N cycle. 

The Paradox Basin in the Colorado Plateau (USA) has some of the most iconic records of paleofluid flow, including sandstone bleaching and ore mineralization, and hydrocarbon, CO2, and He reservoirs, yet the sources of fluids responsible for these extensive fluid-rock reactions are highly debated. This study, for the first time, characterizes fluids within the basin to constrain the sources and emergent behavior of paleofluid flow resulting in the iconic rock records. Major ion and isotopic (δ18Owater; δDwater; δ18OSO4; δ34SSO4; δ34SH2S; 87Sr/86Sr) signatures of formation waters were used to evaluate the distribution and sources of fluids and water-rock interactions by comparison with the rock record. There are two sources of salinity in basinal fluids: (1) diagenetically altered highly evaporated paleo-seawater-derived brines associated with the Pennsylvanian Paradox Formation evaporites; and (2) dissolution of evaporites by topographically driven meteoric circulation. Fresh to brackish groundwater in the shallow Cretaceous Burro Canyon Formation contains low Cu and high SO4 concentrations and shows oxidation of sulfides by meteoric water, while U concentrations are higher than within other formation waters. Deeper brines in the Pennsylvanian Honaker Trail Formation were derived from evaporated paleo-seawater mixed with meteoric water that oxidized sulfides and dissolved gypsum and have high 87Sr/86Sr indicating interaction with radiogenic siliciclastic minerals. Upward migration of reduced (hydrocarbon- and H2S-bearing) saline fluids from the Pennsylvanian Paradox Formation along faults likely bleached sandstones in shallower sediments and provided a reduced trap for later Cu and U deposition. The distribution of existing fluids in the Paradox Basin provides important constraints to understand the rock record over geological time.