Sidney Hemming

Last updated

Sidney Ann Rasbury Hemming
Alma mater State University of New York at Stony Brook
Scientific career
Institutions Lamont–Doherty Earth Observatory
Thesis Pb isotope studies of sedimentary rocks and detrital components for provenance analysis  (1994)
Doctoral advisor Scott McLennan

Sidney Hemming is an analytical geochemist known for her work documenting Earth's history through analysis of sediments and sedimentary rocks. She is a professor of earth and environmental sciences at Columbia University.

Contents

Education and career

Hemming earned a BS from Midwestern University in 1983 and an MS from Tulane University in 1986. [1] In 1994 she earned her PhD from Stony Brook where she studied lead isotopes in sedimentary rocks. [2] In 1994, Hemming started a postdoc with Wally Broecker at Lamont–Doherty Earth Observatory. [3] [4] As of 2021, Hemming is a professor of earth and environmental sciences at Lamont–Doherty Earth Observatory.

In 2018, Hemming was named a fellow of the American Geophysical Union who cited her "for the development of geochemical and isotopic tracers for sediments to reveal geological processes and events through Earth's history". [5] In 2021, Hemming received a Guggenheim Fellowship which she plans to use to study the time period between the Pliocene and the Pleistocene. [4]

Research

Hemming's research documents changes in Earth's history using the chemical signals in sedimentary rocks and sediments. She uses geochronology to obtain age estimates of events occurring in the ocean thereby tracking changes in water circulation, winds, and glaciers. She has used neodymium isotopes to track rapid changes in Antarctic Intermediate Water [6] and changes in North Atlantic Deep Water. [7] In the southern Ocean, Hemming has used strontium isotopes in sediments to track changes in the strength of the Agulhas current during the Last Glacial Maximum [8] and constrained the location of the Antarctic Circumpolar Current. [9] In California, her research on past climate conditions at Mono Lake [10] [11] revealed chemical signatures in the sediments recorded the Laschamp event, a global geomagnetic shift. [12] [13] [14] In the North Atlantic Ocean, Hemming's research on Heinrich events [15] has constrained the amount of ice-rafted debris moved by icebergs into the North Atlantic Ocean. [16]

Selected publications

Awards and honors

Related Research Articles

<span class="mw-page-title-main">Ice age</span> Period of long-term reduction in temperature of Earths surface and atmosphere

An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and greenhouse periods, during which there are no glaciers on the planet. Earth is currently in the Quaternary glaciation. Individual pulses of cold climate within an ice age are termed glacial periods, and intermittent warm periods within an ice age are called interglacials or interstadials.

<span class="mw-page-title-main">Snowball Earth</span> Worldwide glaciation episodes during the Proterozoic eon

The Snowball Earth hypothesis proposes that, during one or more of Earth's icehouse climates, the planet's surface became entirely or nearly entirely frozen. It is believed that this occurred sometime before 650 myr during the Cryogenian period. Proponents of the hypothesis argue that it best explains sedimentary deposits that are generally believed to be of glacial origin at tropical palaeolatitudes and other enigmatic features in the geological record. Opponents of the hypothesis contest the geological evidence for global glaciation and the geophysical feasibility of an ice- or slush-covered ocean, and they emphasize the difficulty of escaping an all-frozen condition. A number of unanswered questions remain, including whether Earth was a full snowball or a "slushball" with a thin equatorial band of open water. The snowball-Earth episodes are proposed to have occurred before the sudden radiation of multicellular bioforms known as the Cambrian explosion. The most recent snowball episode may have triggered the evolution of multicellularity.

The Younger Dryas, which occurred circa 12,900 to 11,700 years BP, was a return to glacial conditions which temporarily reversed the gradual climatic warming after the Last Glacial Maximum (LGM), which lasted from circa 27,000 to 20,000 years BP. The Younger Dryas was the last stage of the Pleistocene epoch that spanned from 2,580,000 to 11,700 years BP and it preceded the current, warmer Holocene epoch. The Younger Dryas was the most severe and long lasting of several interruptions to the warming of the Earth's climate, and it was preceded by the Late Glacial Interstadial, an interval of relative warmth that lasted from 14,670 to 12,900 BP.

<span class="mw-page-title-main">Agulhas Current</span> Western boundary current of the southwest Indian Ocean that flows down the east coast of Africa

The Agulhas Current is the western boundary current of the southwest Indian Ocean. It flows south along the east coast of Africa from 27°S to 40°S. It is narrow, swift and strong. It is suggested that it is the largest western boundary current in the world ocean, with an estimated net transport of 70 sverdrups, as western boundary currents at comparable latitudes transport less — Brazil Current, Gulf Stream, Kuroshio.

<span class="mw-page-title-main">Heinrich event</span> Large groups of icebergs traverse the North Atlantic.

A Heinrich event is a natural phenomenon in which large groups of icebergs break off from the Laurentide Ice Sheet and traverse the Hudson Strait into the North Atlantic. First described by marine geologist Hartmut Heinrich, they occurred during five of the last seven glacial periods over the past 640,000 years. Heinrich events are particularly well documented for the last glacial period but notably absent from the penultimate glaciation. The icebergs contained rock mass that had been eroded by the glaciers, and as they melted, this material was dropped to the sea floor as ice rafted debris forming deposits called Heinrich layers.

The Older Dryas was a stadial (cold) period between the Bølling and Allerød interstadials, about 14,000 years Before Present, towards the end of the Pleistocene. Its date is not well defined, with estimates varying by 400 years, but its duration is agreed to have been around 200 years.

Paleoceanography is the study of the history of the oceans in the geologic past with regard to circulation, chemistry, biology, geology and patterns of sedimentation and biological productivity. Paleoceanographic studies using environment models and different proxies enable the scientific community to assess the role of the oceanic processes in the global climate by the re-construction of past climate at various intervals. Paleoceanographic research is also intimately tied to paleoclimatology.

The environmental isotopes are a subset of isotopes, both stable and radioactive, which are the object of isotope geochemistry. They are primarily used as tracers to see how things move around within the ocean-atmosphere system, within terrestrial biomes, within the Earth's surface, and between these broad domains.

Professor Henry "Harry" Elderfield, was Professor of Ocean Chemistry and Palaeochemistry at the Godwin Laboratory in the Department of Earth Sciences at the University of Cambridge. He made his name in ocean chemistry and palaeochemistry, using trace metals and isotopes in biogenic carbonate as palaeochemical tracers, and studying the chemistry of modern and ancient oceans - especially those of the glacial epoch and the Cenozoic.

<span class="mw-page-title-main">Maureen Raymo</span> American paleoclimatologist and marine geologist

Maureen E. "Mo" Raymo is an American paleoclimatologist and marine geologist. She is the Co-Founding Dean of the Columbia Climate School, Director of the Lamont–Doherty Earth Observatory of Columbia University, the G. Unger Vetlesen Professor of Earth & Environmental Sciences, and Director of the Lamont–Doherty Core Repository at the Lamont–Doherty Earth Observatory of Columbia University. She is the first female climate scientist and first female scientist to head the institution.

<span class="mw-page-title-main">Giant current ripples</span> Depositional forms in channeled scablands

Giant current ripples, Giant gravel bars, Gravel dunes or GCR's, are a form of subaqueous dune. They are active channel topographic forms up to 20 m high, which occur within near-thalweg areas of the main outflow routes created by glacial lake outburst floods. Giant current ripple marks are large scale analogues of small current ripples formed by sand in streams. Giant current ripple marks are important features associated with scablands. As a landscape component, they are found in several areas that were previously in the vicinity of large glacial lakes.

Provenance in geology, is the reconstruction of the origin of sediments. The Earth is a dynamic planet, and all rocks are subject to transition between the three main rock types: sedimentary, metamorphic, and igneous rocks. Rocks exposed to the surface are sooner or later broken down into sediments. Sediments are expected to be able to provide evidence of the erosional history of their parent source rocks. The purpose of provenance study is to restore the tectonic, paleo-geographic and paleo-climatic history.

Ouki was an ancient lake in the Bolivian Altiplano. Its existence was postulated in 2006 by a group of scientists which had subdivided the Lake Minchin lake cycle in several subcycles. The Lake Minchin cycle had been previously identified in 1904 as a now disappeared lake in the central Altiplano. Sediments attributed to Lake Minchin may be part of Ouki instead. The dating is uncertain, with radiocarbon and uranium-thorium dating yielding different dates spanning the time between 28,200 and 125,990 ± 9,580 years ago.

Jean Lynch-Stieglitz is a paleoceanographer known for her research on reconstructing changes in ocean circulation over the last 100,000 years.

Catherine Chauvel is a geochemist at the Institut de Physique du Globe de Paris known for her research on the impact of volcanic activity on the chemistry of the mantle, continental crust, and island arc geochemistry.

Delia Wanda Oppo is an American scientist who works on paleoceanography where she focuses on past variations in water circulation and the subsequent impact on Earth's climate system. She was elected a fellow of the American Geophysical Union in 2014.

<span class="mw-page-title-main">Geological event</span> Earth

A geological event is a temporally and spatially heterogeneous and dynamic (diachronous) happening in Earth history that contributes to the transformation of Earth system and the formation of geological strata. Event stratigraphy was first proposed as a system for the recognition, study and correlation of the effects of important physical or biological events on the broader stratigraphical record.

Global paleoclimate indicators are the proxies sensitive to global paleoclimatic environment changes. They are mostly derived from marine sediments. Paleoclimate indicators derived from terrestrial sediments, on the other hand, are commonly influenced by local tectonic movements and paleogeographic variations. Factors governing the earth climate system include plate tectonics, which controls the configuration of continents, the interplay between the atmosphere and the ocean, and the earth's orbital characteristics. Global paleoclimate indicators are established based on the information extracted from the analyses of geologic materials, including biological, geochemical and mineralogical data preserved in marine sediments. Indicators are generally grouped into three categories; paleontological, geochemical and lithological.

The Agulhas Leakage is an inflow of anomalously warm and saline water from the Indian Ocean into the South Atlantic due to the limited latitudinal extent of the African continent compared to the southern extension of the subtropical super gyre in the Indian Ocean. The process occurs during the retroflection of the Agulhas Current via shedding of anticyclonic Agulhas Rings, cyclonic eddies and direct inflow. The leakage contributes to the Atlantic Meridional Overturning Circulation (AMOC) by supplying its upper limb, which has direct climate implications.

<span class="mw-page-title-main">Offshore freshened groundwater</span> Water located in the sub-seafloor

Offshore freshened groundwater(OFG) is water that contains a Total Dissolved Solid (TDS) concentration lower than sea water, and which is hosted in porous sediments and rocks located in the sub-seafloor. OFG systems have been documented all over around the world and have an estimated global volume of around 1 × 106 km3. Their study is important because they may represent an unconventional source of potable water for human populations living near the coast, especially in areas where groundwater resources are scarce or facing stress

References

  1. ↑ "sidney | Lamont–Doherty Earth Observatory". www.ldeo.columbia.edu. Retrieved August 14, 2021.
  2. ↑ Hemming, Sidney Ann Rasbury (1994). Pb isotope studies of sedimentary rocks and detrital components for provenance analysis (Thesis). OCLC   31235173.
  3. 1 2 "John Simon Guggenheim Foundation | Sidney R. Hemming" . Retrieved August 15, 2021.
  4. 1 2 3 "Sidney Hemming, Paleoclimate Detective, Wins Guggenheim Fellowship". State of the Planet. April 13, 2021. Retrieved August 15, 2021.
  5. 1 2 "Hemming". Honors Program. Retrieved August 14, 2021.
  6. ↑ Pahnke, Katharina; Goldstein, Steven L.; Hemming, Sidney R. (2008). "Abrupt changes in Antarctic Intermediate Water circulation over the past 25,000 years". Nature Geoscience. 1 (12): 870–874. Bibcode:2008NatGe...1..870P. doi:10.1038/ngeo360. ISSN   1752-0894.
  7. ↑ Rutberg, Randye L.; Hemming, Sidney R.; Goldstein, Steven L. (2000). "Reduced North Atlantic Deep Water flux to the glacial Southern Ocean inferred from neodymium isotope ratios". Nature. 405 (6789): 935–938. Bibcode:2000Natur.405..935R. doi:10.1038/35016049. ISSN   1476-4687. PMID   10879531. S2CID   205007120.
  8. ↑ Franzese, Allison M.; Hemming, Sidney R.; Goldstein, Steven L. (2009). "Use of strontium isotopes in detrital sediments to constrain the glacial position of the Agulhas Retroflection". Paleoceanography. 24 (2): n/a. Bibcode:2009PalOc..24.2217F. doi:10.1029/2008PA001706. ISSN   1944-9186.
  9. ↑ Hemming, S. R.; Flierdt, T. van de; Goldstein, S. L.; Franzese, A. M.; Roy, M.; Gastineau, G.; Landrot, G. (2007). "Strontium isotope tracing of terrigenous sediment dispersal in the Antarctic Circumpolar Current: Implications for constraining frontal positions". Geochemistry, Geophysics, Geosystems. 8 (6): n/a. Bibcode:2007GGG.....8.6N13H. doi: 10.1029/2006GC001441 . ISSN   1525-2027. S2CID   13915405.
  10. ↑ "Climate change and the future of Mono Lake". phys.org. December 13, 2013. Retrieved August 15, 2021.{{cite web}}: CS1 maint: url-status (link)
  11. ↑ Colman, S. M.; Hemming, S. R.; Stine, S.; Zimmerman, S. R. H. (2014). "The effects of recent uplift and volcanism on deposition in Mono Lake, California, from seismic-reflection (CHIRP) profiles: MONO LAKE CHIRP". Journal of Geophysical Research: Solid Earth. 119 (5): 3955–3970. doi: 10.1002/2013JB010726 .
  12. ↑ Kent, D.V.; Hemming, S.R.; Turrin, B.D. (April 2002). "Laschamp Excursion at Mono Lake?". Earth and Planetary Science Letters. 197 (3–4): 151–164. Bibcode:2002E&PSL.197..151K. doi:10.1016/S0012-821X(02)00474-0. ISSN   0012-821X.
  13. ↑ Zimmerman, Susan H.; Hemming, Sidney R.; Kent, Dennis V.; Searle, Stephanie Y. (2006). "Revised chronology for late Pleistocene Mono Lake sediments based on paleointensity correlation to the global reference curve". Earth and Planetary Science Letters. 252 (1–2): 94–106. Bibcode:2006E&PSL.252...94Z. doi:10.1016/j.epsl.2006.09.030. S2CID   53422433.
  14. ↑ Cox, Stephen E.; Farley, Kenneth A.; Hemming, Sidney R. (2012). "Insights into the age of the Mono Lake Excursion and magmatic crystal residence time from (U‐Th)/He and 230Th dating of volcanic allanite". Earth and Planetary Science Letters. 319–320: 178–184. Bibcode:2012E&PSL.319..178C. doi:10.1016/j.epsl.2011.12.025.
  15. ↑ Hemming, Sidney R. (2004). "Heinrich events: Massive late Pleistocene detritus layers of the North Atlantic and their global climate imprint". Reviews of Geophysics. 42 (1). Bibcode:2004RvGeo..42.1005H. doi: 10.1029/2003RG000128 . ISSN   1944-9208. S2CID   53526029.
  16. ↑ Downing, Greg E.; Hemming, Sidney R.; Jost, Anne; Roy, Martin (September 30, 2013). "40Ar/39Ar hornblende provenance clues about Heinrich event 3 (H3)". Geological Society, London, Special Publications. 378 (1): 245–263. doi:10.1144/sp378.18. ISSN   0305-8719. S2CID   128891292.
  17. ↑ "GSA Fellowship". www.geosociety.org. Retrieved August 15, 2021.
  18. ↑ "About the Geochemistry Fellow Honor" . Retrieved August 15, 2021.{{cite web}}: CS1 maint: url-status (link)
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.