Process dominance shift in solute chemistry as revealed by long-term high-frequency water chemistry observations of groundwater flowing through weathered argillite underlying a steep forested hillslope

Kim, Hyojin; Bishop, James K. B.; Dietrich, W. E.; Fung, Inez

doi:10.1016/j.gca.2014.05.011

Cited by 53 publications

(75 citation statements)

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“…This saturation with respect to metastable alluminosilicate secondary clays is expected and has been observed in both stream/river waters (e.g., Gíslason and Eugster, 1987;Eiriksdottir et al, 2013) and soils White et al, 2009;Kim et al, 2014). Of the clay minerals, samples from both chemostatic and nonchemostatic catchments are closer to saturation (log(IAP/K = 0) with halloysite (and imogolite), and highly supersaturated with respect to kaolinite and the smectite endmembers.…”

Section: Saturation Indices Of Primary and Secondary Mineralssupporting

confidence: 54%

“…Of the clay minerals, samples from both chemostatic and nonchemostatic catchments are closer to saturation (log(IAP/K = 0) with halloysite (and imogolite), and highly supersaturated with respect to kaolinite and the smectite endmembers. Since halloysite and imogolite are thought to be metastable precursors Maher et al, 2009;White et al, 2009;Kim et al, 2014) and are closer to equilibrium compared to kaolinite or smectite (Fig. 8), this may justify the use of halloysite (or imogolite) in reaction path reactive transport modeling instead of kaolinite or smectite (e.g., ).…”

Section: Saturation Indices Of Primary and Secondary Mineralsmentioning

confidence: 99%

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Paleoclimate Constraints on Terrestrial Hydroclimate, Silicate Weathering, and the Carbon Cycle

Ibarra¹

2018

Preprint

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Maintenance of a habitable planet requires connections and balance among Earth’s biogeochemical cycles. Further, the strength of the feedbacks and couplings determines the stability of conditions in the surface climate system necessary for the evolution of life. Records of Earth’s past climate, paleoclimate records, provide constraints beyond the reach of the instrumental record on the directionality, strength and co-evolution of key Earth system cycles. This includes the geologic carbon cycle, the water cycle and the planet’s energy balance. Crucially, the geography, topography and lithology of Earth’s continents have two important features that are the focus of this dissertation. First, the continents provide boundary conditions that determine global circulation and hydroclimate patterns that couple Earth’s water and carbon cycles (Chapters 1 and 2). Second, the land surface provides a stabilizing negative feedback in the form of silicate weathering fluxes (Chapters 3 and 4, and Appendix E), balancing the long-term carbon cycle through alkalinity and solute delivery to the oceans, and subsequent carbonate burial. In this dissertation I use data, observations and modeling to place mechanistic constraints on how interactions between Earth’s surface and long-term biogeochemical cycles maintain balance and habitable conditions in our climate system conducive for the evolution of life. Fundamental to understanding our climate system is predicting the anticipated sign of terrestrial hydroclimate change during periods of climatic change. To this end I have investigated the regional response of hydroclimate change using paleoclimate records from mid-latitude lake systems. First, in Chapter 1, I have developed an inverse model to quantify how a mid-latitude lake system in Asia, the Songliao Basin, responded to a transient warming event during the Cretaceous. This model was also applied to a Holocene ostracod record from Lake Miragoane, Haiti. Second, in Chapter 2, I compile spatial distributions and size estimates of pluvial lake systems in western North America during the Pliocene-Pleistocene. By imposing mass and energy balance constraints (sensu Budyko) I forward modeled lake area distributions to demonstrate that now-arid western North America was wetter during both past colder and warmer periods during the Pliocene-Pleistocene, a result not predicted for future warming scenarios. Geologic observations primarily suggest wetter conditions globally during warmer-than-present periods. Importantly, this observation is a requirement for the operation of the stabilizing negative feedback between silicate weathering and climate. Understanding the factors that control silicate weathering rates is fundamental to constraining the evolution of Earth’s carbon cycle over geologic timescales. One challenge for reconstructing past weathering rates is determining the reactivity of Earth’s surface. In Chapter 3 I have quantified the reactivity of modern basalt and granite catchments using a process-based solute production model and concentration-discharge weathering relationships. This approach provides mechanisms that link runoff (i.e., terrestrial hydroclimate changes that were the focus of Chapters 1 and 2) with the distribution of global sub-aerial silicate lithologies. In Chapter 4 I utilize an emerging metal isotope system, lithium isotopes, to investigate the terrestrial weathering response to a large perturbation in the carbon cycle during the Cretaceous. We determine that the background-state of the Cretaceous weathering system was more congruent and, hence, more sensitive to perturbations in the carbon cycle than during the Neogene. Finally, in Appendix E I have quantified how step-wise geologic evolution of land plants strengthened the silicate weathering feedback over the Phanerozoic. I have developed a new reactive transport framework for evaluating the relative plant-controlled roles of hydrologic versus thermodynamic mechanisms that influence the coupling between the water cycle and silicate weathering fluxes on a continental scale. The results described in this dissertation constrain links between two connected portions of the exogenic Earth system. I have provided constraints for how the land surface records past changes in regional atmospheric circulation patterns, as well as regional water and energy balances. Further, using reactive transport modeling, I have placed new constraints on the role of plants and lithology in determining the coupling between terrestrial hydroclimate and weathering. Collectively these results suggest that the surface Earth system, our planet’s fluid envelope, has been progressively tuned by the advent of continents and the evolution of life. [Note: this is the non-embargoed portion of my dissertation]

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Section: Saturation Indices Of Primary and Secondary Mineralssupporting

confidence: 54%

Section: Saturation Indices Of Primary and Secondary Mineralsmentioning

confidence: 99%

Paleoclimate Constraints on Terrestrial Hydroclimate, Silicate Weathering, and the Carbon Cycle

Ibarra¹

2018

Preprint

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“…Representative elemental ratios taken from rivers draining exclusively silicate and carbonate lithology are shown for reference (Gaillardet et al 1999). Kim et al (2014) previously hypothesized that water entering the vadose zone quickly reacts with the regolith, resulting in increased solute concentrations. This reactivity is driven by the pCO 2 of infiltrating rainwater, and thus the rate at which water moves through the vadose zone relative to the rate at which it reacts with the solid phase dictates the depth into the subsurface that the fluid reaches before equilibrating (and thus no longer driving chemical weathering).…”

Section: Discussionmentioning

confidence: 99%

“…2 Calcium and magnesium normalized to sodium concentrations measured in all depths of the VMS with representative silicate and carbonate endmembers (Gaillardet et al 1999) illustrated. Ion ratios for average rainwater collected at the site, and groundwater measured in wells 1, 3, and 10 at high flow and low flow rates are taken from Kim et al (2014). Data are colored based on the sampling date, and span a range of time from February to November of 2016…”

Section: Discussionmentioning

confidence: 99%

Seasonal shifts in the solute ion ratios of vadose zone rock moisture from the Eel River Critical Zone Observatory

et al. 2017

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One of the greatest challenges in critical zone studies is to document the moisture dynamics, water flux, and solute chemistry of the unsaturated, fractured and weathered bedrock that lies between the soil and groundwater table. The central impediment to quantifying this component of the subsurface is the difficulty associated with direct observations. Here, we report solute chemistry as a function of depth collected over a full year across the shale-derived vadose zone of the Eel River Critical Zone Observatory using a set of novel sub-horizontal wellbores, referred to as the vadose zone monitoring system. The results of this first geochemical glimpse into the deep vadose zone indicate a dynamic temporal and depth-resolved structure. Major cation concentrations reflect seasonal changes in precipitation and water saturation, and normalized ratios span the full range of values reported for the world's largest rivers.

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“…Subsequent rain in the winter advances a wetting front through the weathered bedrock zone and delivers water to a dynamic, fractured controlled groundwater response system (Salve et al, 2012). Graduate student led research has been initiated on: (1) prediction of the Critical Zone develop ment (Rempe and Dietrich, 2014); (2) dynamics of runoff and rock moisture availability to the forest canopy (Oshun et al, 2012); (3) chemical evolution of water and gasses through the Critical Zone (Kim et al, 2012(Kim et al, , 2014; and (4) influence of vegetation on regional climate (Link et al, 2014).…”

Section: Figure 225 Location Of Rivendell Site On Elder Creek (Rightmentioning

confidence: 99%

The Role of Critical Zone Observatories in Critical Zone Science

White¹,

Brantley²,

Banwart³

et al. 2015

Developments in Earth Surface Processes

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Process dominance shift in solute chemistry as revealed by long-term high-frequency water chemistry observations of groundwater flowing through weathered argillite underlying a steep forested hillslope

Cited by 53 publications

References 52 publications

Paleoclimate Constraints on Terrestrial Hydroclimate, Silicate Weathering, and the Carbon Cycle

Paleoclimate Constraints on Terrestrial Hydroclimate, Silicate Weathering, and the Carbon Cycle

Seasonal shifts in the solute ion ratios of vadose zone rock moisture from the Eel River Critical Zone Observatory

The Role of Critical Zone Observatories in Critical Zone Science

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