A5059555811- Geology and Paleoclimatology Research
- Cryospheric studies and observations
- Isotope Analysis in Ecology
- Atmospheric and Environmental Gas Dynamics
- Polar Research and Ecology
- Atmospheric chemistry and aerosols
- Atmospheric Ozone and Climate
- Chemical Analysis and Environmental Impact
- Methane Hydrates and Related Phenomena
- Groundwater and Isotope Geochemistry
- Water Treatment and Disinfection
- Aeolian processes and effects
- Climate variability and models
- Tree-ring climate responses
- Pleistocene-Era Hominins and Archaeology
- Climate change and permafrost
- Planetary Science and Exploration
- Arctic and Antarctic ice dynamics
- Atmospheric aerosols and clouds
- Geophysics and Gravity Measurements
- Winter Sports Injuries and Performance
- Radioactivity and Radon Measurements
- Mass Spectrometry Techniques and Applications
- Electrochemical Analysis and Applications
- Marine and coastal ecosystems
South Dakota State University
2015-2024
Avera Health
2018-2023
University of California, San Diego
2003
The Ohio State University
1995-1999
An ice core record from the Guliya cap on Qinghai-Tibetan Plateau provides evidence of regional climatic conditions over last glacial cycle. 36 Cl data suggest that deepest 20 meters may be more than 500,000 years old. The δ 18 O change across Termination I is ∼5.4 per mil, similar to in Huascarán (Peru) and polar cores. Three interstadials (Stages 3, 5a, 5c) are marked by increases values Holocene Eemian (∼124,000 ago). similarity this pattern CH 4 records cores indicates global levels...
Two ice cores from the col of Huascarán in north-central Andes Peru contain a paleoclimatic history extending well into Wisconsinan (Würm) Glacial Stage and include evidence Younger Dryas cool phase. stage conditions at high elevations tropics appear to have been as much 8° 12°C cooler than today, atmosphere contained about 200 times dust, Amazon Basin forest cover may less extensive. Differences both oxygen isotope ratio δ 18 O (8 per mil) deuterium excess (4.5 Late Holocene are comparable...
Abstract. We present the WD2014 chronology for upper part (0–2850 m; 31.2 ka BP) of West Antarctic Ice Sheet (WAIS) Divide (WD) ice core. The is based on counting annual layers observed in chemical, dust and electrical conductivity records. These are caused by seasonal changes source, transport, deposition aerosols. measurements were interpreted manually with aid two automated methods. validated comparing to high-accuracy, absolutely dated chronologies. For Holocene, cosmogenic isotope...
Abstract. The injection of sulfur into the stratosphere by volcanic eruptions is dominant driver natural climate variability on interannual to multidecadal timescales. Based a set continuous sulfate and records from suite ice cores Greenland Antarctica, HolVol v.1.0 database includes estimates magnitudes approximate source latitudes major stratospheric (VSSI) events for Holocene (from 9500 BCE or 11 500 years BP 1900 CE), constituting an extension previous record 7000 years. incorporates...
Sulfuric acid aerosols produced in the stratosphere following massive volcanic eruptions possess a mass‐independent sulfur isotopic signature, acquired when SO 2 experiences UV photooxidation. The data are consistent with laboratory photooxidation experiments using light at 248 nm (maximum absorption of ozone), whereas anomalies previously observed Archean samples photodissociation 190–220 nm. A mechanism photooxidation, occurring early stage stratospheric plume, range 220–320 (weak band ),...
Climate records indicate that the decade of AD 1810–1819 including “the year without a summer” (1816) is probably coldest during past 500 years or longer, and cause climatic extreme has been attributed primarily to 1815 cataclysmic Tambora eruption in Indonesia. But cold temperatures early part timing call into question real impact volcanic eruptions. Here we present new evidence, based on sulfur isotope anomaly (Δ 33 S), unique indicator sulfuric acid produced stratosphere preserved polar...
Abstract Of the natural forcings causing short‐term climatic variations, volcanism, along with its impact, is perhaps best understood. The primary net result of impact reduced receipt solar energy at Earth's surface due to scattering incoming radiation by secondary sulfate aerosols formed from volcanic sulfur. quantitative effects can be measured in energy‐balance‐based climate models, which require validation using high‐quality paleoclimatic and paleovolcanic data. An important advancement...
Significance Cold and dry glacial-state climate conditions persisted in the Southern Hemisphere until approximately 17.7 ka, when paleoclimate records show a largely unexplained sharp, nearly synchronous acceleration deglaciation. Detailed measurements Antarctic ice cores document exactly at that time unique, ∼192-y series of massive halogen-rich volcanic eruptions geochemically attributed to Mount Takahe West Antarctica. Rather than coincidence, we postulate halogen-catalyzed stratospheric...
Significance The specific cause of the long-term decrease in stable nitrogen isotope ratio ( 15 N/ 14 N) ice core nitrate beginning ∼1850 is a subject debate, hindering efforts to understand changes global cycle. Our high-resolution record N combined with model calculations suggests that mainly caused by equilibrium shift gas−particle partitioning atmospheric due increasing acidity resulting from anthropogenic emissions and sulfur oxides. also reveals leveling off ∼1970, synchronous sulfate...
Abstract A comprehensive record (WHV2020) of explosive volcanic eruptions in the last 11,000 years is reconstructed from West Antarctica Ice Sheet Divide deep ice core (WDC). The chronological list 426 large Southern Hemisphere and low latitudes during Holocene are highest quality all records cores, owing to high‐resolution chemical measurement exceptionally accurate WDC timescale. No apparent trend found frequency (number per millennium) eruptions, number most recent millennium (1,000–2,000...
Extensive archives of volcanic history are available from ice cores recovered the Antarctic and Greenland sheets that receive preserve sulfuric acid fallout explosive eruptions. The continuous, detailed (average 1.2 samples per year) sulfate measurements a 200‐m core remote East Antarctica site (Plateau Remote) provide record Southern Hemisphere volcanism over last 4100 years. This extends beyond 1000 years covered by previous cores. An average 1.3 eruptions century is recorded in snow...
The continuous sulfate analysis of two Antarctic ice cores, one from the Peninsula region and West Antarctica, provides an annually resolved proxy history southern semisphere volcanism since early in 15th century. dating is accurate within ±3 years due to high rate snow accumulation at both core sites small sample sizes used for analysis. records are consistent with each other. A systematic objective method separating outstanding events background flux proposed identify all volcanic signals....
The reconstruction of past volcanism from glaciological archives is based on the measurement sulfate concentrations in ice. This method does not allow a proper evaluation climatic impact an eruption owing to uncertainty classifying event between stratospheric or tropospheric. work develops new method, using anomalous sulfur isotope composition volcanic order identify eruptions over last millennium. advantages and limits this are established with examination 10 largest signals ice cores Dome...
Abstract The WAIS (West Antarctic Ice Sheet) Divide deep ice core was recently completed to a total depth of 3405 m, ending 50 m above the bed. Investigation visual stratigraphy and grain characteristics indicates that column at drilling location is undisturbed by any large-scale overturning or discontinuity. climate record developed from this therefore likely be continuous robust. Measured grain-growth rates, recrystallization characteristics, grain-size response transitions fit within...
A primary goal of the SCAR (Scientific Committee for Antarctic Research) initiated AntClim21 (Antarctic Climate in 21st Century) Scientific Research Programme is to develop analogs understanding past, present and future climates Southern Hemisphere. In this contribution we provide a framework achieving that includes: description basic climate parameters; comparison existing reanalyses; ice core sodium records as proxies frequencies marine air mass intrusion spanning past ∼2000 years. The...
Abstract Variability in sea ice is a critical climate feedback, yet the seasonal behavior of Southern Hemisphere and across multiple timescales remains unclear. Here, we develop seasonally resolved Holocene salt record using major ion measurements South Pole Ice Core (SPC14). We combine SPC14 data with GEOS‐Chem chemical transport model to demonstrate that primary source switches from open water (summer) (winter), wintertime variations disproportionately responsible for centennial millennial...
Decades of research have focused on establishing the exact year and climatic impact Minoan eruption Thera, Greece (c.1680 to 1500 BCE). Ice cores offer key evidence resolve this controversy, but attempts been hampered by a lack multivolcanic event synchronization between records. In study, Antarctic Greenland ice-core records are synchronized using double bipolar sulfate marker, calendar dates assigned each revealed within 'Thera period'. From global-scale sequence volcanic loading, we...
Measurement of trace chemical impurities in ice cores contributes to the reconstruction records atmospheric environment and climate system. Ion chromatography (IC) is an effective analytical technique for ionic species but has been used on discretely prepared samples, resulting extensive slow sample preparation potential contamination. A new developed that utilizes IC as online detection a melter-based continuous flow system quantitative determination major impurities. The system, called...
[1] A record of explosive eruptions over the last 1830 years reconstructed from a South Pole, Antarctica, ice core extends coverage volcanic history to start first millennium A.D. The dating by annual layer counting carries an uncertainty ±2% number time markers, with largest error ±20 at bottom 182 m core. Several aspects methodology detecting and quantifying sulfate signals in cores are examined developing this record. new is remarkably consistent previous Pole records. A comparison...
Abstract A detailed history of volcanism covering the last 2840 years is reconstructed from top 100.42 m a 109.91 ice core Dome (DA2005 core), East Antarctica. Using two known volcanic stratigraphic markers, mean accumulation rate during period AD 1260-1964 found to be 23.2 mmw.e. -1 , consistent with previously reported at A. This used date entire core. Volcanic eruptions in 840 BC-AD1998 are detected as outstanding sulphate events. Seventy-eight identified, 2.7 per century. Comparisons...
Abstract. Sulfate is an important component of global atmospheric aerosol, and has partially compensated for greenhouse gas-induced warming during the industrial period. The magnitude direct indirect radiative forcing aerosols since preindustrial times a large uncertainty in climate models, which been attributed largely to uncertainties environment. Here, we report observations oxygen isotopic composition (Δ17O) sulfate aerosol collected remote marine boundary layer (MBL) spring summer order...
Abstract. The South Pole Ice Core (SPICEcore) was drilled in 2014–2016 to provide a detailed multi-proxy archive of paleoclimate conditions East Antarctica during the Holocene and late Pleistocene. Interpretation these records requires an accurate depth–age relationship. Here, we present SPICEcore (SP19) timescale for age ice SPICEcore. SP19 is synchronized WD2014 chronology from West Antarctic Sheet Divide (WAIS Divide) core using stratigraphic matching 251 volcanic events. These events...
Abstract The Arctic is warming at almost four times the global rate. An estimated sixty percent of greenhouse‐gas‐induced has been offset by anthropogenic aerosols, but contribution aerosols to radiative forcing (RF) represents largest uncertainty in estimating total RF, largely due unknown preindustrial aerosol abundance. Here, sulfur isotope measurements a Greenland ice core show that passive volcanic degassing contributes up 66 ± 10% sulfate years without major eruptions. A...