Browsing by Author "Baldini, LM"

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    A climate-isotope regression model with seasonally-varying and time-integrated relationships
    (Springer, 2011-12-01) Fischer, MJ; Baldini, LM
    This study investigates multivariable and multiscalar climate-delta(18)O relationships, through the use of statistical modeling and simulation. Three simulations, of increasing complexity, are used to generate time series of daily precipitation delta(18)O. The first simulation uses a simple local predictor (daily rainfall amount). The second simulation uses the same local predictor plus a larger-scale climate variable (a daily NAO index), and the third simulation uses the same local and non-local predictors, but with varying seasonal effect. Since these simulations all operate at the daily timescale, they can be used to investigate the climate-delta(18)O patterns that arise at daily-interannual timescales. These simulations show that (1) complex links exist between climate-delta(18)O relationships at different timescales, (2) the short-timescale relationships that underlie monthly predictor-delta(18)O relationships can be recovered using only monthly delta(18)O and daily predictor variables, (3) a comparison between the simulations and observational data can elucidate the physical processes at work. The regression models developed are then applied to a 2-year dataset of monthly precipitation delta(18)O from Dublin and compared with event-scale data from the same site, which illustrates that the methodology works, and that the third regression model explains about 55% of the variance in delta(18)O at this site. The methodology introduced here can potentially be applied to historic monthly delta(18)O data, to better understand how multiple-integrated influences at short timescales give rise to climate-delta(18)O patterns at monthly-interannual timescales. © 2011, Springer.
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    Global analysis reveals climatic controls on the oxygen isotope composition of cave drip water
    (Springer Nature, 2019-07-05) Baker, AA; Hartmann, A; Duan, WH; Hankin, SI; Comas-Bru, L; Cuthbert, MO; Treble, PC; Banner, J; Genty, D; Baldini, LM; Bartolomé, M; Moreno, A; Pérez-Mejías, C; Werner, M
    The oxygen isotope composition of speleothems is a widely used proxy for past climate change. Robust use of this proxy depends on understanding the relationship between precipitation and cave drip water δ18O. Here, we present the first global analysis, based on data from 163 drip sites, from 39 caves on five continents, showing that drip water δ18O is most similar to the amount-weighted precipitation δ18O where mean annual temperature (MAT) is < 10 °C. By contrast, for seasonal climates with MAT > 10 °C and < 16 °C, drip water δ18O records the recharge-weighted δ18O. This implies that the δ18O of speleothems (formed in near isotopic equilibrium) are most likely to directly reflect meteoric precipitation in cool climates only. In warmer and drier environments, speleothems will have a seasonal bias toward the precipitation δ18O of recharge periods and, in some cases, the extent of evaporative fractionation of stored karst water. © 2019, The Author(s)
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    Global distribution and controls on cave drip water oxygen isotope composition
    (Australasian Quaternary Association Inc, 2018-12-10) Baker, AA; Hartmann, A; Duan, WH; Hankin, SI; Comas-Bru, L; Cuthbert, MO; Treble, PC; Banner, J; Genty, D; Baldini, LM; Bartolomé, M; Moreno, A; Pérez-Mejías, C
    The oxygen isotope composition of speleothems is a widely utilised paleoclimate proxy that is responsible for the current state-of-knowledge of past Asian monsoon dynamics, the timing of glacial-interglacial cycles, and the insolation control on inter-tropical convergence zone position, among other climate processes. Because speleothems are deposited by cave drip water, and this is derived from meteoric precipitation, it is critical to understand the empirical relationship between precipitation and cave drip water d18O. Here, we present the first global analysis, based on data from 148 drip sites, 38 caves, and five continents. Globally, drip water d18O is most similar to the amount-weighted precipitation d18O where mean annual temperature (MAT) is < 10 °C. For seasonal climates with MAT > 10 °C and < 16 °C, we demonstrate that drip water d18O records the recharge-weighted d18O. Our analysis implies that speleothems (formed in near isotopic equilibrium) are most likely to have d18O that directly reflect meteoric precipitation only in cool climates. In warmer and drier environments, speleothems will have a seasonal bias toward the precipitation d18O of recharge periods and, in some cases, the extent of evaporative fractionation of stored karst water. We highlight the implications of our analysis for the interpretation of oxygen isotope records in Australasian speleothems. © The Authors
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    Global distribution and controls on cave drip water oxygen isotope composition
    (International Union for Quaternary Research (INQUA), 2019-07-30) Baker, AA; Comas-Bru, L; Hartmann, A; Duan, WH; Hankin, SI; Cuthbert, MO; Treble, PC; Banner, J; Gentry, D; Baldini, LM; Bartolomé, M; Moreno, A; Pérez-Mejías, C
    The oxygen isotope composition of speleothems is a widely utilised paleoclimate proxy that is responsible for the current state-of-knowledge of past Asian monsoon dynamics, the timing of glacial-interglacial cycles, and the insolation control on inter-tropical convergence zone position, among other climate processes. Because speleothems are deposited by cave drip water, and this is derived from meteoric precipitation, it is critical to understand the empirical relationship between precipitation and cave drip water δ18O. Here, we present the first global analysis, based on data from 148 drip sites, 38 caves, and five continents. Globally, drip water δ18O is most similar to the amount-weighted precipitation δ18O where mean annual temperature (MAT) is < 10 °C. For seasonal climates with MAT > 10 °C and < 16 °C, we demonstrate that drip water δ18O records the recharge-weighted δ18O. Our analysis implies that speleothems (formed in near isotopic equilibrium) are most likely to have δ18O that directly reflect meteoric precipitation only in cool climates. In warmer and drier environments, speleothems will have a seasonal bias toward the precipitation δ18O of recharge periods and, in some cases, the extent of evaporative fractionation of stored karst water.
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    An investigation of the controls on Irish precipitation δ18O values on monthly and event timescales.
    (Springer, 2010-11) Baldini, LM; McDermott, F; Baldini, JUL; Fischer, MJ; Mollhoff, M
    This two-year study investigates the relative influence of meteorological variables (precipitation amount and temperature), atmospheric circulation, air mass history, and moisture source region on Irish precipitation oxygen isotopes (δ18Op) on event and monthly timescales. Single predictor correlations reveal that on the event scale, 20% of δ18Op variability is attributable to the amount effect and 7% to the temperature effect while on the monthly timescale the North Atlantic Oscillation accounts for up to 20% of δ18Op variability and the amount and temperature effects are not significant. In comparison, multivariate linear regression reveals that the interaction of temperature and precipitation amount explains up to 40% of δ18Op variance at event and monthly timescales. Five-day kinematic back trajectories suggest that the amount-weighted mean δ18Op value of southerly- and northerly-derived events are lower by 2‰ relative to events derived from the west. Because air mass history and atmospheric circulation appear to influence δ18Op in Ireland, Irish paleo-δ18Op proxy records are best interpreted as reflecting a combination of parameters, not just paleotemperature or paleorainfall. © 2010, Springer.