Stratigraphy of climate change
Download
1 / 30

Stratigraphy of climate change - PowerPoint PPT Presentation


  • 178 Views
  • Updated On :

Stratigraphy of climate change. Lecture 19. The predominant power in this spectrum is at about 100,000, 41,000 and 19-23,000 years. from Alley, 2000. The Milankovitch hypothesis: climate change results from changes in Earth’s orbital parameters. Barbados.

Related searches for Stratigraphy of climate change

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Stratigraphy of climate change' - finian


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.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript


Slide3 l.jpg

from Alley, 2000 41,000 and 19-23,000 years

The Milankovitch hypothesis: climate change results from changes in Earth’s orbital parameters


Slide4 l.jpg

Barbados 41,000 and 19-23,000 years


Slide5 l.jpg

Today we’ll look at examples of climate changes seen in the stratigraphic record that are NOT controlled by orbital parameters


Orbital forcing ice cores l.jpg
Orbital Forcing – Ice Cores the stratigraphic record that are NOT controlled by orbital parameters

  • Ice core 18O records temperature

  • Orbital frequencies are clearly dominant, but higher frequencies are present


Heinrich events l.jpg
Heinrich Events the stratigraphic record that are NOT controlled by orbital parameters

  • Discovered in 1988 in marine sediment cores

  • Recognized as distinct layers with significant increase in lithic fragments, and large clasts in some areas


Heinrich layer isopachs l.jpg
Heinrich Layer Isopachs the stratigraphic record that are NOT controlled by orbital parameters

  • Double maxima in isopachs

  • Layers thicken to NW into Labrador Sea


Source of heinrich events l.jpg
Source of Heinrich events the stratigraphic record that are NOT controlled by orbital parameters

  • Black areas are regions with large carbonate deposits

  • Sediment must have been ice-rafted


Heinrich layer 4 40 000 years bp l.jpg
Heinrich Layer 4 (~40,000 years BP) the stratigraphic record that are NOT controlled by orbital parameters

18O in polar planktonic foraminifera

Modeling shows about 250-year duration and 2-m rise in sea level

Nature, Roche et al., 2004



Heinrich events in context l.jpg
Heinrich Events in context level

  • Occur at times of coldest weather in N. Atlantic

  • Followed by a sharp warming

  • No clear periodicity

Bond 1993 figure


Summary of heinrich events l.jpg
Summary of Heinrich events level

  • Effects are global – signature of Heinrich events has been found around the world

  • Massive discharge of ice into N. Atlantic from the Laurentide ice sheet is well established

  • No clear explanation for such dynamics in the ice sheet


Dansgaard oeschger events l.jpg
Dansgaard-Oeschger Events level

  • Characterized by rapid warming in the N. Atlantic, followed by slower cooling

  • Quasi-Periodic, with a timescale of ~1400 years

  • Recorded by diverse climate proxies

  • Evidence for global climatic effects

(Data From ftp://ftp.ngdc.noaa.gov/paleo/icecore/greenland/summit/grip/isotopes/gripd18o.txt)


Greenland and d o events l.jpg
Greenland and D-O events level

  • Within the Greenland ice cores, several independent variables all show D-O events prominently

    • 18O – Temperature

    • Ca/Dust concentrations – varying weather in Asia?

    • Na/Cl concentrations – increased storminess in N. Atlantic

    • Etc…


Other evidence of d o events l.jpg
Other Evidence of D-O events level

  • Sediment cores from the Santa Barbara Basin (Hendy and Kennet, 1999)


Other evidence of d o events23 l.jpg
Other Evidence of D-O events level

  • Stalagmites from Eastern China (Wang et al., 2001)


Global map of d o records l.jpg
Global Map of D-O records level

http://www2.ocean.washington.edu/oc540/lec01-31/


Theories for rapid climate change l.jpg
Theories for rapid climate change level

  • Heinrich, D-O periods are too rapid for orbital frequencies

  • Some combination of the ocean/atmosphere/cryosphere must be responsible

  • Need a source with enough power to affect global climate


Atlantic circulation l.jpg

Deep water formation level

Atlantic Circulation

  • Deep Water is formed at the Northern and Southern extents of the Atlantic Ocean

  • This deep circulation has an overturning timescale of ~103 years

  • Surface currents strongly influence climate in many areas, as in the N. Atlantic

Deep water formation


Stratigraphic evidence l.jpg
Stratigraphic Evidence level

  • Recent work (April 2004) has investigated a proxy for Atlantic circulation using a marine sediment core from the Bermuda Rise

  • Th settles out of water faster than Pa, so the ratio between the two can provide information about the strength of flow away from source

  • Result – Atlantic circulation essentially shut down during Heinrich events


Summary l.jpg
Summary level

  • There is still no clear trigger for Heinrich or Dansgaard-Oeschger events, nor an explanation for their periods

  • However, changes in Atlantic circulation seem to account for many of the side effects of both processes

  • More stratigraphic records = more clues


Why it all matters l.jpg

End of Agriculture??? level

Why it all matters

Beginning of Agriculture

  • Late Pleistocene was not simply cold – it was totally chaotic

  • Even modern agricultural processes probably couldn’t overcome such variability


A few references l.jpg
A few references… level

  • Bradley, Raymond S. Paleoclimatology. Harcourt Press, 1999.

  • Siedov et al., Ed. The Oceans and rapid climate change. AGU, 2001.

  • Hesse, R. and Khodabakhsh, S. Depositional Facies of Late Pleistocene Heinrich Events I nthe Labrador Sea. Geology 26:2 103-106, 1998.

  • Dansgaard, W et al. Evidence for general instability of past climate from a 250kyr ice-core record. Nature 364, 15 July 1993.

  • Bond, G. et al. Evidence for massive discharges of icebergs into the North Atlantic Ocean during the last glacial period. Nature 360, 19 Nov. 1992.

  • Sarnthein, M. et al. Exploring Late Pleistocene Climate Variations. Eos. 81:51 2000.

  • Bond, G. et al. Correlations between climate records from North Atlantic sediments and Greenland ice. Nature 365, 9 Sept. 1993.

  • Bard, E. Climate Shock: Abrupt changes over Millennial time scales. Physics Today Dec. 2002.

  • Hendy and Kennett. Dansgaard-Oeschger cycles and the California Current System: Planktonic foraminiferal response to rapid climate change in Santa Barbara Basin, Ocean Drilling Program hole 893A. Paleoceanography, 15:1, 2000.

  • Phillips, FM. Climatic and hydrologic oscillations in the Owens Lake basin and adjacent Sierra Nevada, California. Science 274:5288, 1996.

  • Wang, YJ. A High-Resolution Absolute-Dated Late Pleistocene Monsoon Record from Hulu Cave, China. 294:5550, 2001.


ad