A5057911394- Geology and Paleoclimatology Research
- Paleontology and Stratigraphy of Fossils
- Methane Hydrates and Related Phenomena
- Isotope Analysis in Ecology
- Atmospheric and Environmental Gas Dynamics
- Oceanographic and Atmospheric Processes
- Geochemistry and Elemental Analysis
- Coral and Marine Ecosystems Studies
- Geological and Geochemical Analysis
- Hydrocarbon exploration and reservoir analysis
- Marine Biology and Ecology Research
- Marine and coastal ecosystems
- Astro and Planetary Science
- Climate variability and models
- Planetary Science and Exploration
- Groundwater and Isotope Geochemistry
- CO2 Sequestration and Geologic Interactions
- Geological and Geophysical Studies
- Atmospheric Ozone and Climate
- Marine and environmental studies
- Climate Change and Geoengineering
- Tree-ring climate responses
- Climate Change Policy and Economics
- Geological Studies and Exploration
- Carbon Dioxide Capture Technologies
Harvard University Press
2008-2024
Planetary Science Institute
2015-2024
Harvard University
2014-2024
Baldwin Wallace University
2021
McGill University
2015
University of Oxford
2015
Princeton University
1996-2010
Massachusetts Institute of Technology
2007-2010
University of Cambridge
2009
Arizona State University
2009
Negative carbon isotope anomalies in carbonate rocks bracketing Neoproterozoic glacial deposits Namibia, combined with estimates of thermal subsidence history, suggest that biological productivity the surface ocean collapsed for millions years. This collapse can be explained by a global glaciation (that is, snowball Earth), which ended abruptly when subaerial volcanic outgassing raised atmospheric dioxide to about 350 times modern level. The rapid termination would have resulted warming...
The gradual discovery that late Neoproterozoic ice sheets extended to sea level near the equator poses a palaeoenvironmental conundrum. Was Earth's orbital obliquity > 60° (making tropics colder than poles) for 4.0 billion years following lunar‐forming impact, or did climate cool globally some reason point at which runaway ice‐albedo feedback created `snowball' Earth? high‐obliquity hypothesis does not account major features of glacial record such as abrupt onsets and terminations...
Research Article| September 01, 2005 Toward a Neoproterozoic composite carbon-isotope record Galen P. Halverson; Halverson 1Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, Massachusetts 02138-2902, USA, Department Earth, Atmospheric, Institute Technology, Building 54-1126, 02139, USA Search for other works by this author on: GSW Google Scholar Paul F. Hoffman; Hoffman 2Department Daniel Schrag; Schrag Adam C. Maloof; Maloof A. Hugh N. Rice...
High-resolution carbon isotope measurements of multiple stratigraphic sections in south China demonstrate that the pronounced isotopic excursion at Permian-Triassic boundary was not an isolated event but first a series large fluctuations continued throughout Early Triassic before ending abruptly early Middle Triassic. The unusual behavior cycle coincides with delayed recovery from end-Permian extinction recorded by fossils, suggesting direct relationship between Earth system function and...
Studies of deeply buried, sedimentary microbial communities and associated biogeochemical processes during Ocean Drilling Program Leg 201 showed elevated prokaryotic cell numbers in sediment layers where methane is consumed anaerobically at the expense sulfate. Here, we show that extractable archaeal rRNA, selecting only for active community members these ecosystems, dominated by sequences uncultivated Archaea affiliated with Marine Benthic Group B Miscellaneous Crenarchaeotal Group, whereas...
We use pore fluid measurements of the chloride concentration and oxygen isotopic composition from Ocean Drilling Program cores to reconstruct salinity temperature deep ocean during Last Glacial Maximum (LGM). Our data show that temperatures Pacific, Southern, Atlantic oceans LGM were relatively homogeneous within error freezing point seawater at ocean's surface. glacial stratification was dominated by variations, in contrast with modern ocean, for which plays a primary role. During Southern...
The Neoproterozoic was an era of great environmental and biological change, but a paucity direct precise age constraints on strata from this time has prevented the complete integration these records. We present four high-precision U-Pb ages for rocks in northwestern Canada that constrain large perturbations carbon cycle, major diversification depletion microfossil record, onset Sturtian glaciation. A volcanic tuff interbedded with glacial deposits, dated at 716.5 million years ago, is...
Pore fluids from the upper 60 meters of sediment 3000 below surface tropical Atlantic indicate that oxygen isotopic composition (delta18O) seawater at this site during last glacial maximum was 0.8 ± 0.1 per mil higher than it is today. Combined with delta18O change in benthic foraminifera region, elevated ratio indicates temperature deep water Ocean 4°C colder maximum. Extrapolation to a global average suggests ice volume contribution 1.0 mil, which partially reconciles...
The Third Way Because organic carbon contains a larger fraction of the light isotope 12 C than inorganic carbonate, variations in isotopic record sedimentary rocks are thought to represent changes amount buried as sediments (and thus removed from rest cycle). Schrag et al. (p. 540 ; see Perspective by Canfield and Kump ) suggest that historically third component was important: authigenic carbonate. Authigenic carbonate is not produced any appreciable quantity today, but much more abundant...
Stabilizing the concentration of atmospheric CO 2 may require storing enormous quantities captured anthropogenic in near-permanent geologic reservoirs. Because subsurface temperature profile terrestrial storage sites, stored these reservoirs is buoyant. As a result, portion injected can escape if reservoir not appropriately sealed. We show that injecting into deep-sea sediments <3,000-m water depth and few hundred meters sediment provides permanent even with large geomechanical...
Carbon sequestration from large sources of fossil fuel combustion, particularly coal, is an essential component any serious plan to avoid catastrophic impacts human-induced climate change. Scientific and economic challenges still exist, but none are enough suggest that carbon capture storage will not work at the scale required offset trillions tons dioxide emissions over next century. The challenge whether technology be ready when society decides it time get going.
An active microbial assemblage cycles sulfur in a sulfate-rich, ancient marine brine beneath Taylor Glacier, an outlet glacier of the East Antarctic Ice Sheet, with Fe(III) serving as terminal electron acceptor. Isotopic measurements sulfate, water, carbonate, and ferrous iron functional gene analyses adenosine 5'-phosphosulfate reductase imply that consortium facilitates catalytic cycle. These metabolic pathways result from limited organic carbon supply because absence contemporary...
A method for rapid determination of high‐precision Sr/Ca ratios in scleractinian corals is presented. Using an inductively coupled plasma atomic emission spectrophotometer, samples are corrected instrument drift using a reference solution, similar to the approach used analysis stable isotopes gas‐source mass spectrometry. Further correction variation ratio with Ca concentration accomplished internal standards. The precision, once all corrections have been made, better than 0.1% (relative...
We explore the applicability of paired Mg/Ca and 18 O/ 16 O measurements on benthic foraminifera from Southern Ocean site 747 to paleoceanographic reconstructions pre‐Pleistocene timescales. focus late Oligocene through Pleistocene (27–0 Ma) history paleotemperatures evolution δ values seawater (δ sw ) at a temporal resolution ∼100–200 kyr. Absolute paleotemperature estimates depend assumptions how ratios have changed over past 27 Myr, but relative changes that occur geologically brief...
We present a 271-year record of Sr/Ca variability in coral from Rarotonga the South Pacific gyre. Calibration with monthly sea surface temperature (SST) satellite and ship measurements made grid measuring 1 degrees by over period 1981 to 1997 indicates that this is an excellent proxy for SST. Comparison SST since 1950 5 also shows data accurately decadal changes The entire back 1726 distinct pattern variability, repeated interdecadal regime shifts greater than 0. 75 C. climate North Pacific,...
The Snowball Earth hypothesis explains the development of glaciation at low latitudes in Neoproterozoic, as well associated iron formations and cap carbonates, terms a runaway ice‐albedo feedback leading to global followed by an extreme greenhouse climate. initiation snowball is linked variety unusual perturbations carbon cycle operating over different timescales, evidenced patterns isotopic composition marine carbonate. Thus theory for why multiple glaciations happened this time, not...
A review of the literature has found a factor 4 spread in estimated values energy penalty for post-combustion capture and storage CO2 from pulverized-coal (PC) fired power plants. We elucidate cause that by deriving an analytic relationship thermodynamic principles identifying which variables are most difficult to constrain. define CCS be fraction fuel must dedicated fixed quantity work output. That can manifest itself as either additional required maintain plant's output or loss constant...
Radiocarbon (14C) content of surface waters inferred from a coral record the Galapagos Islands increased abruptly during upwelling season (July through September) after El Nino event 1976. Sea-surface temperatures (SSTs) associated with also shifted The synchroneity shift in both 14C and SST implies that vertical thermal structure eastern tropical Pacific changed This change may be responsible for increase frequency intensity events since