The Holocene and

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The Holocene and Solar Variability
Longer Timescales
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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
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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 correlation to
  climate record into LGM

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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.

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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
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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

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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.