Papers by Jihong Cole-Dai
Geophysical Research Letters
Perchlorate has been observed in many environments on Earth and Mars but its sources remain poorl... more Perchlorate has been observed in many environments on Earth and Mars but its sources remain poorly quantified. In this study, we use a global three‐dimensional chemical transport model to simulate perchlorate's gas‐phase photochemical production, atmospheric transport, and deposition on Earth's surface. Model predictions are compared to newly compiled observations of atmospheric concentrations, deposition flux, and oxygen isotopic composition of perchlorate. We find that the modeled gas‐phase production of perchlorate is consistent with reported stratospheric observations. Nevertheless, we show that this mechanism alone cannot explain the high levels of perchlorate observed at many near‐surface sites (aerosol concentrations >0.1 ng m−3 and deposition fluxes >10 g km−2 yr−1) or the low 17O‐excess observed in perchlorate sampled from pristine environments (<+18.4‰). We discuss four hypotheses to explain the model‐observation discrepancies and recommend laboratory and ...
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Atmospheric Chemistry and Physics
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AGU Fall Meeting Abstracts, Dec 1, 2019
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Geophysical Research Letters, 2021
Variability in sea ice is a critical climate feedback, yet the seasonal behavior of Southern Hemi... more Variability in sea ice is a critical climate feedback, yet the seasonal behavior of Southern Hemisphere sea ice and climate across multiple timescales remains unclear. Here, we develop a seasonally resolved Holocene sea salt record using major ion measurements of the South Pole Ice Core (SPC14). We combine the SPC14 data with the GEOS‐Chem chemical transport model to demonstrate that the primary sea salt source switches seasonally from open water (summer) to sea ice (winter), with wintertime variations disproportionately responsible for the centennial to millennial scale structure in the record. We interpret increasing SPC14 and circum‐Antarctic Holocene sea salt concentrations, particularly between 8 and 10 ka, as reflecting a period of winter sea ice expansion. Between 5 and 6 ka, an anomalous drop in South Atlantic sector sea salt indicates a temporary sea ice reduction that may be coupled with Northern Hemisphere cooling and associated ocean circulation changes.
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The West Antarctic Ice Sheet (WAIS) Divide deep ice core WD2014 chronology, consisting of ice age... more The West Antarctic Ice Sheet (WAIS) Divide deep ice core WD2014 chronology, consisting of ice age, gas age, delta-age and uncertainties therein. The West Antarctic Ice Sheet Divide (WAIS Divide, WD) ice core is a newly drilled, high-accumulation deep ice core that provides Antarctic climate records of the past ~68 ka at unprecedented temporal resolution.The upper 2850 m (back to 31.2 ka BP; Sigl et al., 2015, Sigl et al., 2016) have been dated using annual-layer counting based on counting of annual layers observed in the chemical, dust and electrical conductivity records. The measurements were interpreted manually and with the aid of two automated methods. We validated the chronology by comparing of the cosmogenic isotope records of 10Be from WAIS Divide and 14C for IntCal13. We demonstrated that over the Holocene WD2014 was consistently accurate to better than 0.5% of the age.The chronology for the deep part of the core (below 2850m; 67.8-31.2 ka BP; Buizert et al., 2015) is based ...
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Atmospheric Environment, 2019
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Melter-based continuous chemical analysis of ice cores has been increasingly employed in ice core... more Melter-based continuous chemical analysis of ice cores has been increasingly employed in ice core research for fast, high resolution measurements of the chemical impurities in snow and ice. In continuous flow analysis (CFA), a heated melter generates uncontaminated flowing streams of ice core meltwater which are channeled directly into measurement devices, such as spectrophotometers, mass spectrometers and flow injection analyzers.
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We examined the solid fraction of melt water from a depth of 361.45-361.55 meters in the GISP2 ic... more We examined the solid fraction of melt water from a depth of 361.45-361.55 meters in the GISP2 ice core. This subbottom depth covers the time from 536.15 to 536.66 A.D. roughly from February 24th to August 28th, 536 A.D.[1,2]. Earlier work measured a Cl value of 64 ppb from 535.9 to 536.2 A.D. roughly from November 24th, 535 A.D. to
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Published data on melt water from the Siple Dome ice core show distinct anomalies at 1443.16 A.D.... more Published data on melt water from the Siple Dome ice core show distinct anomalies at 1443.16 A.D. The Ca value is 111 ppb, over 9 times the next highest Ca value between 850-1760 A.D. The K value is 20 ppb, about 1.4 times the next highest K value. The Ca anomaly may be due to partial dissolution of CaCO3 microfossils
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Sulfur dioxide from natural and anthropogenic sources is oxidized in the atmosphere to form sulfu... more Sulfur dioxide from natural and anthropogenic sources is oxidized in the atmosphere to form sulfuric acid aerosols. These aerosols contribute to acid rain, global climate variations, and are a health hazard to humans. Sulfuric acid aerosols in the stratosphere may also affect ozone levels. Volcanic eruptions are a natural source of sulfur dioxide, but depending on the height of the eruption plume, an eruption can be either tropospheric or stratospheric. It has been found in Antarctic ice cores that sulfate from a stratospheric eruption contains sulfur-33 MIF anomaly, while there is no anomaly when sulfur dioxide is oxidized in the troposphere. The unique sulfur MIF signature for stratospheric eruptions could be a valuable tool to identify large, climate-impacting stratospheric eruptions in ice core records. Modeling studies suggest that the main cause of this sulfur MIF is photochemical reactions induced by high-energy UV light below 310 nm. This is consistent with the Antarctica ic...
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Science, 1998
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ACS Symposium Series, 2015
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Annals of Glaciology, 1999
A 36C1 peak has been found at about 37 ka BP in the Guliya ice core, drilled from the Qinghai-Tib... more A 36C1 peak has been found at about 37 ka BP in the Guliya ice core, drilled from the Qinghai-Tibetan Plateau. This peak is indicative of enhanced cosmogenic isotope production in the atmosphere, rather than a change in accumulation rate. Comparison with the records of 10Be and 36C1 in ice cores from Antarctica and Greenland indicates that peaks of the cosmogenic isotopes are global, and that they can be used as time markers for dating ice cores. Interestingly, the 37 ka BP global event coincided with a cold period.
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Atmospheric Environment
Abstract Surface snow along a 1250-km transect from the coast to the East Antarctic ice sheet sum... more Abstract Surface snow along a 1250-km transect from the coast to the East Antarctic ice sheet summit Dome Argus are used to investigate factors influencing spatial variability of perchlorate (ClO4−) production and deposition, and to explore contributions from tropospheric and stratospheric sources to ClO4− in Antarctic snow. The average ClO4− concentration of 104.3 ± 33.3 ng kg−1 is in the range of previously reported ClO4− concentrations in Antarctic snow, and one to two orders of magnitude higher than those in Arctic snow. The transect profile of ClO4− concentration shows relatively small spatial variability and no single consistent trend, with apparently high concentrations at locations with low accumulation rate. In the coastal region, strong correlation between ClO4− and troposphere-produced nitrate (NO3−) is observed. This may indicate that ClO4− in the coastal region is formed predominantly in the troposphere during summer, and the contribution from the stratosphere may be negligibly small. The lack of apparent correlation between ClO4− and NO3− in snow in interior East Antarctica suggests that a significant amount of ClO4− may be of stratospheric origin, with some tropospheric production. No significant correlation is found between sea-salt chloride (Cl−) and ClO4− in the coastal region, suggesting that tropospheric sea-salt Cl− is probably not an important precursor of ClO4− in snow in this region. In the inland Dome A region, part of Cl− might be converted into ClO4−.
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Chinese Science Bulletin
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Papers by Jihong Cole-Dai