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Ice Free World??. Presented by: Akindele Balogun. The Earth is warmer today than it has been in many millennia. Questions: How warm has the earth been in the past? What caused the warming? How would the world be different if this was the case?. Was it always this way??.
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Ice Free World?? Presented by: Akindele Balogun.
The Earth is warmer today than it has been in many millennia. Questions: • How warm has the earth been in the past? • What caused the warming? • How would the world be different if this was the case?
LPTM/PETM(~55mya) • Paleocene- Eocene Thermal Maximum (also referred to as Late Paleocene Thermal Maximum). • Onset of both the thermal maximum and the Carbon Isotope Excursion (CIE) • Short-term biotic and paleoenvironmental changes
LPTM vs. PETM? • Late Paleocene Thermal Maximum • Paleocene-Eocene Thermal Maximum
LPTM vs. PETM? • Late Paleocene Thermal Maximum • Paleocene-Eocene Thermal Maximum
Cause of warming (Greenhouse Effect) • Release of CO2, CH4 and H2O into the atmosphere. • Dissociation of methane hydrates -Volcanism - Comet Impact • Failure of Carbon reservoir i.e. continental slopes
Evidence in Support of Ice Free World. • Warm-adapted vegetation (preserved at poles) • Global Sea level rise • Isotope data (Oxygen and Carbon)
High resolution records of the LPTM and circum-Caribbean volcanism: is there a casual link? Brawler et. al. (1997) • Rapid and changes in stable carbon isotope is due to volcanism • Volcanic activity in the Caribbean warmed high latitude waters – causing deep water supply from low latitude. • Dissociation of Methane hydites from warming deep waters. • Problem- Climate model and observed tropical warming in the LPTM are at odds with volcanic CO2 induced warming Mechanism.
Case for tropical warming • δ13C excursion at PETM coincides with small but significant decrease in δ18O - Indicating rise in SST. • Diminished CaCO3 at sites reflect shoaling of lysocline and CCD – CaCO3 dissolution is consistent with addition of massive amounts of carbon from the oxidized methane hydrates (Acidic Condition) • Lack of evidence of observed tropical warming is attributed to circum-Caribbean eruptions – Stratospheric sulfate aerosols (e.g. Pinatubo (1991). • Tephra (volcaniclasts) layers are more abundant in the PETM indicating lots of volcanic activity.
Benthic foraminifera extinction in the PETM, carbonate shift due to carbon isotope depletion during claystone diagenesis; formation of sulphides
Carbon cycling and chronology of climate warming during the Paleocene/Eocene transition.Norris and Rohl(1999) • Suggests that large shifts in δ13C at the PETM is due to dissociation of Methane hydrates – injection of 1,200-2000 gtons of Carbon into Ocean & atmosphere • Used magnetochronology to establish that timing of –ive CIE coincides with extinction of benthic forams • Methane or another source supplied carbon into the atmosphere & oceans faster than it could be removed by burial. • Residence time of Carbon=120kyrs – similar to modeled response after massive input of methane • CO2 induced greenhouse warming due to collapse of hydrate reservoir and slope failure under warm water.
A case for comet impact trigger for the Paleocene/Eocene thermal maximum and carbon isotope excursion Kent et. al. (2003) • Hypothesize rapid CIE and dissociation of sea floor methane hydrate is as a result of comet impact
Evidence • Indirect evidence of impact- abundance of magnetic nanoparticles in Kaolinite rich shelf sediments • Sudden increase in kaolinite is thought to represent the redeposition on the marine shelf of rapidly weathered impact ejecta • Supporting evidence - Iridium anomaly at Paleocene/Eocene boundary • Anomalously high magnetized sediment were found at CIE