Showing papers by "Ellen Thomas published in 2020"
Yale University1, Institute for Geosciences and Natural Resources2, University of Potsdam3, University of California, San Diego4, National Oceanography Centre, Southampton5, Texas A&M University6, University of Zaragoza7, University of Rennes8, University College London9, Pennsylvania State University10, Aix-Marseille University11, University of Minnesota12, University of Münster13, University of Bremen14, Heidelberg University15, Leipzig University16, University of Edinburgh17, University of Utah18, Max Planck Society19, Waseda University20, Baylor University21, University of Hawaii22, ConocoPhillips23, Institute of Arctic and Alpine Research24, Open University25, Harvard University26, Geological Survey of Denmark and Greenland27, Massachusetts Institute of Technology28, Wesleyan University29, University of California, Santa Cruz30
TL;DR: Carbon cycle modeling and paleotemperature records are used to constrain the timing of volcanogenic outgassing and found support for major out gassing beginning and ending distinctly before the impact, with only the impact coinciding with mass extinction and biologically amplified carbon cycle change.
Abstract: The cause of the end-Cretaceous mass extinction is vigorously debated, owing to the occurrence of a very large bolide impact and flood basalt volcanism near the boundary. Disentangling their relative importance is complicated by uncertainty regarding kill mechanisms and the relative timing of volcanogenic outgassing, impact, and extinction. We used carbon cycle modeling and paleotemperature records to constrain the timing of volcanogenic outgassing. We found support for major outgassing beginning and ending distinctly before the impact, with only the impact coinciding with mass extinction and biologically amplified carbon cycle change. Our models show that these extinction-related carbon cycle changes would have allowed the ocean to absorb massive amounts of carbon dioxide, thus limiting the global warming otherwise expected from postextinction volcanism.
169 citations
TL;DR: It is found that high-latitude temperatures were almost as warm after the initiation of Antarctic glaciation as before, challenging basic understanding of how climate works, and of the development of climate and ice volume through time.
Abstract: Falling atmospheric CO2 levels led to cooling through the Eocene and the expansion of Antarctic ice sheets close to their modern size near the beginning of the Oligocene, a period of poorly documented climate. Here, we present a record of climate evolution across the entire Oligocene (33.9 to 23.0 Ma) based on TEX86 sea surface temperature (SST) estimates from southwestern Atlantic Deep Sea Drilling Project Site 516 (paleolatitude ∼36°S) and western equatorial Atlantic Ocean Drilling Project Site 929 (paleolatitude ∼0°), combined with a compilation of existing SST records and climate modeling. In this relatively low CO2 Oligocene world (∼300 to 700 ppm), warm climates similar to those of the late Eocene continued with only brief interruptions, while the Antarctic ice sheet waxed and waned. SSTs are spatially heterogenous, but generally support late Oligocene warming coincident with declining atmospheric CO2. This Oligocene warmth, especially at high latitudes, belies a simple relationship between climate and atmospheric CO2 and/or ocean gateways, and is only partially explained by current climate models. Although the dominant climate drivers of this enigmatic Oligocene world remain unclear, our results help fill a gap in understanding past Cenozoic climates and the way long-term climate sensitivity responded to varying background climate states.
47 citations
01 May 2020
45 citations
01 Feb 2020
TL;DR: Harper, DT; Honisch, B; Zeebe, RE; Shaffer, G; Haynes, LL; Thomas, E; and Zachos, JC as mentioned in this paper.
Abstract: Author(s): Harper, DT; Honisch, B; Zeebe, RE; Shaffer, G; Haynes, LL; Thomas, E; Zachos, JC
29 citations
TL;DR: In this paper, high-resolution scanning electron microscopy was used to study the sedimentary record of the aftermath of the Cretaceous-Paleogene (K-Pg) impact at 31 sites globally, with records ranging from the deep ocean to the Chicxulub impact crater, over intervals ranging from a few centimeters to more than seventeen meters.
26 citations
Syracuse University1, University of Oxford2, Heriot-Watt University3, California State University, Bakersfield4, Oklahoma State University–Stillwater5, Royal Holloway, University of London6, Alfred Wegener Institute for Polar and Marine Research7, University of Bremen8, British Antarctic Survey9, Rutgers University10, Wesleyan University11, Yale University12
TL;DR: In this paper, the authors use Holocene benthic foraminifera to explore I/Ca in Cibicidoides spp. as a bottom water oxygen proxy.
23 citations
TL;DR: In this article, the authors used foraminifers from Holocene core-tops (Southeast Atlantic Ocean) to document planktic I/Ca across a range of oceanographic conditions.
21 citations
TL;DR: It is demonstrated that planktic foraminifera reproduce both sexually and asexually and demonstrate extensive phenotypic plasticity in response to nonheritable factors, which fundamentally explain the rapid spatial and temporal response of even imperceptibly low populations of planktic to optimal conditions.
Abstract: Marine protists are integral to the structure and function of pelagic ecosystems and marine carbon cycling, with rhizarian biomass alone accounting for more than half of all mesozooplankton in the oligotrophic oceans. Yet, understanding how their environment shapes diversity within species and across taxa is limited by a paucity of observations of heritability and life history. Here, we present observations of asexual reproduction, morphologic plasticity, and ontogeny in the planktic foraminifer Neogloboquadrina pachyderma in laboratory culture. Our results demonstrate that planktic foraminifera reproduce both sexually and asexually and demonstrate extensive phenotypic plasticity in response to nonheritable factors. These two processes fundamentally explain the rapid spatial and temporal response of even imperceptibly low populations of planktic foraminifera to optimal conditions and the diversity and ubiquity of these species across the range of environmental conditions that occur in the ocean.
20 citations
30 Sep 2020
TL;DR: The I/Ca tracer as discussed by the authors is a proxy for dissolved oxygen in seawater, and its recent applications and some potential future research directions are discussed in detail in a recent review.
Abstract: How oxygen levels in Earth's atmosphere and oceans evolved has always been a central question in Earth System Science. Researchers have developed numerous tracers to tackle this question, utilizing geochemical characteristics of different elements. Iodine incorporated in calcium carbonate (including biogenic) minerals, reported as I/Ca, is a proxy for dissolved oxygen in seawater. Here we review the rationale behind this proxy, its recent applications and some potential future research directions.
7 citations