1 / 57

Pliocene , El Niño and Northern / Southern Hemisphere Glaciation

Pliocene , El Niño and Northern / Southern Hemisphere Glaciation. Mirjam Kosch Florian Suter Alexander Umbricht Andy Eigenmann. Questions. Will the present warm conditions terminate soon, to be followed by the next ice age?

palti
Download Presentation

Pliocene , El Niño and Northern / Southern Hemisphere Glaciation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Pliocene, ElNiñoand Northern / Southern HemisphereGlaciation Mirjam Kosch Florian Suter Alexander Umbricht Andy Eigenmann

  2. Questions • Will the present warm conditions terminate soon, to be followed by the next ice age? • Will the onset of the next ice age be inhibited by the current rise in the atmospheric concentration of GHG induced by humans? • Will that rise restore the warm conditions of the early Pliocene?

  3. Outline • Methods • Southern Hemisphere glaciation • Opening of the Drake Passage • Northern Hemisphere glaciation • Pliocene paradoxon • Hypotheses for Greenland glaciation • Questions and Discussion

  4. 1. Methods

  5. d18O • Terrestrial water enriched in light 16O • Seawater enriched in heavier 18O • Compare 18O/16O of sample with 18O/16O of standard (fossils) University of Vermont

  6. Neodymium Isotopes • eNd(143Nd/144Nd) • Oceanic basins with distinct eNd-values • Crusts and fossil fish teeth preserve eNd-values of bottom water • Bassin connections Wikipedia, 2009

  7. IceRaftedDebris (IRD) • Objects deposited on/within ice shield (Debris) • Iceberg calves • Drifting and melting • Debris deposited onto bottom of the water body Wikipedia, 2009

  8. 2. Southern HemisphereGlaciation

  9. The Drake Passage • Separation of South America and Antarctica • Estimated opening: 49 – 17 Ma • Enables Antarctic Circumpolar Current (ACC) Wikipedia, 2009

  10. The Drake Passage – Indications • Tracking Pacific Seawater • Neodymium ratio eNd • Pacific eNd: -3 to -5 • Atlantic eNd: approximately -9 • Fossil fish teeth gained from sediments • High resolution of benthic Nd signal

  11. The Drake Passage – other possible Influences • Weathering • In general not high enough • Exception: volcanic ash

  12. The Drake Passage – other possible Influences Scotia Sea

  13. The Drake Passage – other possible Influences • Weathering • In general not high enough • Exception: volcanic ashes • Water influx from the Indian Ocean • Water influx from the Panama Seaway

  14. The Drake Passage – otherpossibleInfluences

  15. The Drake Passage – other possible Influences • Weather • In general not high enough • Exception: volcanic ashes • Water influx from the Indian Ocean • Water influx from the Panama Seaway

  16. The Drake Passage – Feedbacks • Enhancement of nutrition upwelling • Stimulation of the biological pump • Lowering of the atmospheric CO2-concentration • Possible reduction of oceanic heat flux

  17. 3. Northern HemisphereGlaciation

  18. Pliocene Paradox • Early Pliocene (5-3 Ma) showed a very different climate state even though the external forcings were practically the same as today.

  19. Climate in early Pliocene (5-3 Ma) • Similarities with today’s climate: • Intensity of sunlight incident on Earth • Global geography • Atmospheric concentration of CO2 • Differences with today’s climate • Higher globally averaged temperatures • No continental glaciers on Northern Hemisphere • Sea level 25 m higher • Permanent El Niño

  20. Climate in late Pliocene (after 3 Ma) • Cooling in the globally averaged temperatures • Collapse of permanent El Niño • Decreasing in atmospheric concentration of CO2 • Appearance of continental glaciers in the Northern Hemisphere

  21. Hypotheses for the Climate Change • Panama Seaway hypothesis • ENSO hypothesis • Uplift hypothesis • CO2 hypothesis

  22. Panama Seaway Hypothesis I • Tectonically driven closure between 13 Ma and 2.5 Ma • Change in salinity gradient • Increase of northward heat transport • Warmer, more evaporative surface water • Increased atmospheric moisture • More snowfall • Increased ice volume in Greenland

  23. Panama Seaway Hypothesis II • Increased northward transport of warm water • Increased summer temperature • Increased evaporation • Significantly increased snowfall

  24. Panama Seaway Hypothesis III Open Panama Seaway • Reduction of ice volume • Warmer summer temperatures lead to an increased ablation • Increased snowfall only leads to a small increase in ice volume Closed Panama Seaway

  25. ENSO Hypothesis • Permanent El Niño state during early Pliocene retarded the onset of Northern Hemisphere glaciation • Loss of permanent El Niño state acted as positive forcing for the onset of glaciation

  26. Key Parameters of El Niño Normal Pacific pattern El Niño conditions NOAA

  27. Today’s SST patterns

  28. ConditionsduringearlyPliocene I

  29. ConditionsduringearlyPliocene II

  30. Correlationbetweenprecipitationand SST

  31. El Niño as contributor to warm conditions • More convective clouds over EEP • Increasing of atmospheric water vapour • Reduced area covered by stratus clouds • Decreasing albedo of the planet

  32. Tropical-Extratropical Coupling • In equilibriumthelossofheat in highlatitudesbalancesthegainofheat in lowlatitudeupwellingregions

  33. Increase in high latitude heat loss Increase in equatorial heat gain Shallower equatorial thermocline Changes in Oceanic Heat Transport • Decrease in high latitude heat loss • Decrease in equatorial heat gain • Deeper equatorial thermocline

  34. Collapse of Permanent El Niño I • Due to global cooling during Cenozoic the temperature of deep ocean decreased • Shoaling of the thermocline • At 3 Ma BP the thermocline became so shallow that wind could bring cold water to the surface in upwelling zones

  35. Collapse of Permanent El Niño II • Only small changes in summer temperature • Northward shift of the Atlantic storm track • Small increase in precipitation, especially in the south

  36. Collapse of Permanent El Niño III Permanent El Niño • Small reduction of ice volume Fluctuation El Niño

  37. Uplift Hypothesis I • Uplift of the Rocky Mountains and the Himalaya • Larger Rossby Wave amplitude • Jet-stream deflection • Cooler air masses www.daukas.com

  38. Uplift Hypothesis II • Cooling in Canada, North Atlantic and Greenland • Generally drier climate over Greenland • Northward deflection of Atlantic storm track leads to greater precipitation over southern Greenland

  39. Uplift Hypothesis III Before tectonic uplift • Increase in snow cover • Cooler summer temperatures lead to less ablation • More precipitation over southern Greenland After tectonic uplift

  40. CO2 Hypothesis I • Decreased radiative forcing • Lowered concentration of atmospheric CO2 • Cooler melt-season temperature • Decreased ablation • Net annual accumulation

  41. CO2 Hypothesis II • Global cooling of 1.3 °C • Decrease in Greenland summer temperatures • Great temperature response at high latitudes, due to albedo feedbacks • Decrease in precipitation (globally and in Greenland)

More Related