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Stalagmite Mg/Ca and Sr/Ca ratios are commonly interpreted as proxies for past hydrologic conditions and are often used to supplement carbon and oxygen stable isotope records. While the processes that control these element ratios, including water-rock interaction, dripwater residence time, and upstream precipitation of calcite, are well understood in continental caves, there have been few investigations of dripwater Element/Ca (X/Ca) evolution in coastal marine caves where seasalt can have a strong influence on the incoming Mg/Ca ratio.We instrumented a marine cave on the remote South Pacific island of Niue to record daily cave microclimate, as well as weekly-integrated drip rates, dripwater oxygen and hydrogen isotopes, and dripwater chemistry over a period of twenty-two months. Using chloride as a conservative tracer for sea-spray, we calculate that seasalt input accounts for a large portion of dripwater Na, SO 4 , and Mg (89%, 93%, and 85% respectively) and a smaller portion of the Ca and Sr (19% and 17%). During the second year of this study a gradual decrease (by $18%) in dripwater chlorinity was observed, suggesting that an epikarsthosted seasalt aerosol inventory was being diluted over time. Minor element to calcium ratios for B, K, Cl, SO 4 , Mg, Na, Sr, and Fe all strongly covary over the observation period, suggesting that although sea-spray plays a significant role in modulating incoming drip chemistry, prior calcite precipitation (PCP) dominates chemical evolution within the epikarst. During a prolonged drought episode, evaporative enrichments in dripwater dD and d 18 O (+4‰ and 0.5‰, respectively) were observed to coincide with increased cation and anion concentrations, strong Ca removal via PCP, and increases in Sr/Ca and Mg/Ca ratios (28% and 34%, respectively), suggesting that concomitant enrichment in speleothem d 18 O and X/Ca ratios may be interpreted as multi-proxy evidence for dry climate conditions. We use modern dripwater chemistry and empirical water-calcite distribution coefficients to predict a range of stalagmite X/Ca ratios. We then forward model a number of scenarios that could modulate stalagmite chemistry, including increased/decreased seasalt input and changing dripwater flow path through calcite, dolomite, and aragonite bedrock. One major implication from this study is that even if PCP and flow path lithology remain constant over time, changing seasalt input can drive stalagmite Mg/Ca and Sr/Ca ratios away from PCP-controlled covariation, and lead to strongly varying http://dx. ScienceDirect Geochimica et Cosmochimica Acta 184 (2016) 289-310Sr/Mg ratios. Thus in order to interpret coastal cave stalagmite X/Ca records accurately, it is necessary to estimate seasalt input and analyze parent drip and bedrock chemistry to quantify the influence of each contributing process.

Long‐range water planning is complicated by factors that are rapidly changing in the 21st century, including climate, population, and water use. Here, we analyze climate factors and drought projections for Texas as an example of a diverse society straddling an aridity gradient to examine how the projections can best serve water stakeholder needs. We find that climate models are robust in projecting drying of summer‐season soil moisture and decreasing reservoir supplies for both the eastern and western portions of Texas during the 21st century. Further, projections indicate drier conditions during the latter half of the 21st century than even the most arid centuries of the last 1,000 years that included megadroughts. To illustrate how accounting for drought nonstationarity may increase water resiliency, we consider generalized case studies involving four key stakeholder groups: agricultural producers, large surface water suppliers, small groundwater management districts, and regional water planning districts. We also examine an example of customized climate information being used as input to long‐range water planning. We find that while stakeholders value the quantitative capability of climate model outputs, more specific climate‐related information better supports resilience planning across multiple stakeholder groups. New suites of tools could provide necessary capacity for both short‐ and long‐term, stakeholder‐specific adaptive planning.

We synthesize the interconnected impacts of Texas’ water and energy resources and infrastructure including the cascading effects due to Winter Storm Uri. The government’s preparedness, communication, policies, and response as well as storm impacts on vulnerable communities are evaluated using available information and data. Where knowledge gaps exist, we propose potential research to elucidate health, environmental, policy, and economic impacts of the extreme weather event. We expect that recommendations made here — while specific to the situation and outcomes of Winter Storm Uri — will increase Texas’ resilience to other extreme weather events not discussed in this paper. We found that out of 14 million residents who were on boil water notices, those who were served by very small water systems went, on average, a minimum of three days longer without potable water. Available county-level data do not indicate vulnerable communities went longer periods of time without power or water during the event. More resolved data are required to understand who was most heavily impacted at the community or neighborhood level. Gaps in government communication, response, and policy are discussed, including issues with identifying — and securing power to — critical infrastructure and the fact that the state’s Emergency Alert System was not used consistently to update Texans during the crisis. Finally, research recommendations are made to bolster weaknesses discovered during and after the storm including (1) reliable communication strategies, (2) reducing disproportionate impacts to vulnerable communities, (3) human health impacts, (4) increasing water infrastructure resilience, and (5) how climate change could impact infrastructure resilience into the future.

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The ventilation of carbon dioxide within subterranean caves regulates the growth of speleothems -mineral deposits found in caves that provide important clues about past climate. While previous studies have used internal temperature measurements to predict ventilation rates, such data would not be available for the task of climate reconstruction. Here, we develop a parsimonious model to predict ventilation rates from knowledge of outside temperatures and the cave's physical dimensions only. In the model, ventilation arises from buoyancy-driven flows created in passageways that connect to the outside. A few key simplifications leads to a system amenable to perturbation analysis, resulting in explicit expressions for ventilation rates. We compare these predictions to time-resolved, in-situ measurements of transported cave gases (carbon dioxide and radon). The theory accurately accounts for the timing and magnitude of seasonal and synoptic variations of these gases, and is therefore diagnostic of seasonal bias in speleothem growth.