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The Holocene and

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Cosmogenic Nuclides. Higher production - weaker solar winds and irradiance. 10Be from ice cores &14C from tree rings ... Centennial-scale cycles with high ... – PowerPoint PPT presentation

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Title: The Holocene and


1
The Holocene and Solar Variability
Longer Timescales
2
Holocene Observations
  • Shifts in surface ocean hydrography
  • Drift ice and cool waters penetrate southwards
    into sub-polar ocean
  • Occur within stable interglacial climate

Bond et al
3
Cosmogenic Nuclides
  • Higher production - weaker solar winds and
    irradiance
  • 10Be from ice cores 14C from tree rings
  • Centennial-scale cycles with high correlation to
    climate record into LGM

4
(No Transcript)
5
Impact at Tropical Latitudes
  • Most recent cycle (100-1100yrs ago) corresponds
    to temperature cycles in Sargasso Sea upwelling
    off W. Africa
  • Oman Record shows Teleconnective response.

6
Oman Record
  • Hoti cave
  • Mid-holocene pluvial period deposition of
    stalagmites
  • d18O record reflects rain fall intensity
  • Shift of ITCZ
  • Varying monsoon

http//www.geo.umass.edu/climate/images/speleofig1
.jpg
7
Oman Record
  • High corrolation between d18O ?14C
  • Likely response to same forcing.
  • Weaker summer monsoon increased Tibetan snow
    cover longer colder Eurasian winters
    decreased NADW formation

8
How Does it Work?
  • Cycles are associated with 0.25 irradiation
    variation
  • Must be internal amplifier
  • Cooler sea surface and ice drift lower surface
    salinity
  • Reduced density in convecting N Atlantic
  • Reduced NADW Formation
  • Solar-triggered reduction in North Atlantic
    thermohaline formation.
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