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Early history of Earth in 1 slide

Early history of Earth in 1 slide. Halliday- Nature 409,2001. Impact hypothesis of Moon origin. 5 hours. 1 hour. Moon contains no volatile elements H,C,N. Moon has much less iron, object impacted differentiated Earth. 1000 years. Oxygen isotope relative abundance same for Earth and Moon.

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Early history of Earth in 1 slide

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  1. Early history of Earth in 1 slide Halliday- Nature 409,2001

  2. Impact hypothesis of Moon origin 5 hours 1 hour • Moon contains no volatile elements H,C,N • Moon has much less iron, object impacted differentiated Earth 1000 years • Oxygen isotope relative abundance same for Earth and Moon 4.1 Ga-oldest rocks on Moon, stabilized by by 3 Ga What about the origin of the oceans? Likely DEGASSED, with some Addition from chondrites and comets. :Website that discusses both. http://www.oceansonline.com/ocean_form.htm

  3. Paleoclimate Overview Longest instrumental climate record: Central England Air Temp From 1659 to the present Peter_Almasi/Spring_2003/Orals_Study_Group

  4. Climate history of the Earth • Solar output has decreased as CO2 increased • Temperature has remained suitable for liquid water over most of • Earth history

  5. Climate: Tertiary to Present

  6. Magnitudes of Climate Variability

  7. History of Pleistocene Study Observations of: climatically displaced faunas Sedimentary processes no longer occurring Moraines, DILUVIALISTS: Biblical Noachian deluge. Poles flooded icebergs rafted boulders "CATASTROPHIST" abrupt, unique event "DRIFT” implies water transport for sediments: till, erratics GLACIALISTS: Glacial Expansion. Emphasis on Uniformitarianism (James Hutton). Called on existing natural processes. Louis Agassiz - Swiss zoologist-paleontologist July 24, 1837 Presidential address, Swiss Society of Natural Science.

  8. European Environmental Sequence Penck and Brueckner, 1909

  9. North American Environmental Sequence Pollen diagrams Function of Production, Dispersion, Preservation, Identification Surface samples provide calibration of pollen-climate relationship

  10. Southwestern US

  11. Ocean Sediment Cores Cores at Deep Sea Sample Repository at Lamont

  12. Ocean Sediment Cores2 • Accumulation rate ranges from 0.21 to 40 cm/ka in open ocean • Low sed rate in deep Pacific, high in Atlantic and on margins • 1872 H.M.S Challenger: first oceanographic expedition • 1950s Maurice Ewing at Lamont: “A core a day.” • Composed of clays (~95%), biogenic tests, volcanic ash, dust and ice-rafted debris (IRD)

  13. Methods of Dating Marine Records • Radiocarbon 0-~45,000 years, calibrated by 14C in tree rings (to 13ka) • and U-Th in annually-banded corals • d18O correlation with ice cores GISP2 or GRIP (very common) • Tuning a d18O record assuming periodic orbital forcing of climate • (Milankovitch cyclicity). SPECMAP chronology of Doug Martinson • et al. (1987) of Lamont-Doherty • Paleomagnetic reversal chronology: Bruhnes-Matuyama at 730 ka • Volcanic Ash Layers (Vedde Ash in North Atlantic at 9.8 ka (14C)

  14. Oxygen isotopes in foraminifera 99.7% 16O 0.2% 18O 0.04% 17O (18O/16O) sample - (18O/16O) SMOW del 18O = \--------------------------------------------x 1000‰ (18O/16O) SMOW • Controlled by Temperature, Salinity, and Global ice volume • Temperature control on fractionation during calcite precipitation • d18O increases 0.22 ‰ per degree C cooling • d18O of ocean water increased 1.2 per mil during glaciations due to • 16O sequestration in continental ice sheets • Formation of sea ice only mildly fractionates oxygen isotopes, • but does increase Salinity of water, so d18O/Salinity varies • T=16.9-4.30(d18Oc-d18Ow)

  15. d18O-Salinity relationship is variable What if it also varies with time? Schmidt, GRL 2002

  16. Oxygen isotope stratigraphy I,II,III Glacial terminations 1-9 Marine isotope stages (MIS) and a-d (substages) Emiliani, 1955 Classic Paper Doug Martinson at Lamont, Quaternary Research (1987)

  17. Insolation at 65 degrees N Constructed using the calculations of Laskar, 1993

  18. Onset of glaciation 2.57 Ma Cooling begins at 3 Ma, but ice-rafted debris appears in North Atlantic by 2.57 Ma. Raymo, 1992

  19. Foraminiferal Transfer Functions Group living fauna into assemblages A-tropical B-subtropical C-subpolar D-polar X-gyre margin assemblage Multivariate Regression Tw = 23.6A + 10.4B + 2.7C + 3.7D + 2.0K (K=constant)

  20. CLIMAP and COHMAP Reconstruction of LGM climate using d 18O and faunal transfer functions CLIMAP-1970s, 1980s comparison of LGM and present climate from COHMAP models climate LGM to the present and compares with proxy data CLIMAP SST data CLIMAP conclude that tropical cooling during LGM was 0-2 degrees. This is in conflict with MOST modern proxy reconstructions

  21. Mg/Ca Paleothermometry Measured in planktic and benthic foraminifera Provides the planktic or benthicwater temperature to calculate salinity changes using d 18O As with d18O, small analytical error

  22. Mg/Ca complications • Insensitive at low temperatures • Calcification depth may vary for planktic • forams; also an issue for d18O • Foram population varies seasonally • Heterogeneous Mg/Ca within foram test • Post-depositional dissolution DECREASES • Mg/Ca resulting in T too COLD

  23. Mg/Ca calibration Lab culture or core top calibrations ElderfieldNature 2000

  24. Paleothermometer comparison Xfer functions Nurnberg Paleoceanography, 2000

  25. Alkenone Paleothermometry Linear realationship between Uk37 and T (Prahl et al. 1988) Uk37 index based on ratio of certain saturated vs. unsaturated ketones found in organic matter of coccolithophores. (E. huxleyi) Alkenones support small cooling of tropics during the glacial. Issues: Coccoliths are very small (~15-30 µm) and may be transported If season of their bloom changes, they will record different T.

  26. Thermohaline Circulation and North Atlantic Deep Water • North Atlantic climate • experiences such strong • variability relative to other • regions because of variable • ocean heat transport. • This transport may be affected • within decades, causing abrupt • jumps in Greenland ice and • North Atlantic climate records.

  27. Great Ocean Conveyor • Thermohaline circulation transports heat and salt to North Atlantic, • warming eastern North America and northern Europe. Gordon (1986) • Involvement in abrupt climate change recognized by Wallace Broecker • of Lamont-Doherty in the late-eighties (1987,1991)

  28. Benthic 13C distribution as water mass tracer Charles and Fairbanks, 1992

  29. 13C/PO4 relationship in forams Atmospheric d13C is -8.5, so invasion of atmospheric CO2 with a temperature decrease lowers d13C of water before isotopic equilibrium, which will eventually raise d13C. Lynch-Stieglitz et al. 1994

  30. Cd/Ca ratio as a nutrient tracer Cd/Ca is promising because it decoupled from the air-sea effects which strongly affect 13C McIntyre GBC 1997

  31. Uncertainties with foram proxies Paleotemperature: Calcification depth may vary with climate. Forams calcify while sinking to ocean floor Paleonutrients: Air-sea exchange high and variable in Nordic Seas affect d13C. Cd/Ca is subject to contamination, requiring large samples and involved sample preparation Vital effects: Calcification rate can vary with light, nutrients, salinity and temperature. This is species and environment specific. Foraminifera may be transported by fast ocean currents, sea ice

  32. Ice-Rafted Detritus (IRD) Concentration of IRD in sediment is related to amount of drifting ice. Generally, MORE IRD in core = COLDER • Grain size 63 microns and above • Can trace iceberg or sea ice provenance • Drifting ice responds to winds and • temperature • The 1500-year cycle in North Atlantic • defined by specific IRD grain • percentages • Largest down-core variations are in • Heinrich events of the North Atlantic Bond et al. (1997)

  33. Terrestrial Climate Records Ice Cores-paleotemperature and atmospheric gases Uplifted marine terraces-sea level Loess-atmospheric response to climate change, vegetation changes Varves-alluviation, productivity, vegetation changes Speleothems-cave deposited calcite-paleotemperature

  34. Ice Cores Records available: d18O (precipitation temperature), CO2, CH4 Sea salt Na (local storminess), non sea-salt K (terrestrial dust), cosmogenic 36Cl, 10Be (solar magnetic activity) • Caveats: • Dating is an issue • (layer counts and • flow modeling) • Gas bubble • inclusion depth • complicates • correlation between • different ice cores

  35. Hemisphericcomparisons in ice core records • GHG positive feedback likely • responsible for climate • connection between the • hemispheres • Glacial-interglacial climate • changes are synchronous, while • higher frequency events appear • ANTIPHASED. This is the • “bipolar seesaw” idea of • Broecker (1998)

  36. Ice core record of greenhouse gases Raynaud QSR 19 2000 GHGs are associated with climate changes. Do they force or respond? Most believe it is an ocean carbon cycle positive feedback to externally-forced climate changes.

  37. YD and ACRappear anti-phased The bi-polar seesaw: If poleward heat transport is shut down in North Atlantic, heat builds up in tropics, southern ocean deep water and thus local climate are warmed. Broecker, 1998

  38. Sea Level Reconstructions BarbadosTerraces, Chappell et al. EPSL (1996) Huon Pensinsula, New Guinea; Esat et al.,Science (1999)

  39. Chinese Loess (wind transported silt) • Climate Sensitive Parameters • Maximum Grain Size • Magnetic Susceptibility George Kukla of Lamont found glacial-interglacial cycles in Czech loess in the 1970s Kukla (1970)

  40. Varves Annually-deposited sediment MECHANICAL- coarse layers/fine layers -sediment color Used in Paleo ENSO reconstructions BIOLOGICAL- Diatoms and Foraminifera

  41. Bog and Lake Pollen Records

  42. Oxygen Isotopes in Speleothems(Cave deposited Calcite) Timing of interglacial events raised questions of accuracy of ocean core d 18O and ice core dating methods.

  43. Lichenometry Lichen grow slowly. Growth curves are developed with local calibration. • Used in surface exposure dating • Dating moraines and flood • deposits Rhizocarpon geographicum

  44. Tree ring width Esper et al., Science 2002 used better de-trending techniques to reveal larger variability for MWP and LIA than before. Solar minima obvious, especially the Maunder Minimum from 1650-1710 AD. Red curve is the Mann et al. Nature 1999 reconstruction used by IPCC

  45. Particular Events in Paleoclimate

  46. The Little Ice Age • Cooling in Europe of • around 1 degree C. • Marked by large climate • extremes both cold and warm • Associated with solar minima Winter market on the Thames, London Grove, 1988

  47. Dansgaard-Oeschger Events in MIS 3 GRIP members, Nature 1993 Caused by a threshold thermohaline circulation responsein the glacial. Distinctive ramping structure to a strong cooling, then rapid warming. (“Bond cycles”)

  48. Climate Impact of Heinrich and D-O events Broecker and Hemming, 2001

  49. Tropical Climate during LGM • COHMAP: Climatic change in tropics was minimal: 0 - 2 C • Current thinking: 3 - 6 oC colder in tropics, 12-16 C at poles • snow lines 1000 m lower in tropics (Rind & Peteet, 1985) • tropical glaciers 18O/16O indicate 8 - 12 C colder (Thompson et al., 1995) • vegetation zones lower in Brasil (Clapperton, 1993) • ocean coral Sr/Ca ratios indicate 6 C colder (Stiute et al., 1995) • heat transport by oceans (8.2-4.6 C) colder (Webb et al 1997)

  50. Paleo ENSO reconstructions

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