1. Holocene climate change - facts and mysteries
IMSC11, Edinburgh
Tuesday, July 13, 2010
Heinz Wanner and Research Team
Oeschger Centre for Climate Change Research
University of Bern, Switzerland

2. Some facts first Holocene climate change 4. September 2019
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Holocene climate change
Some facts first
4. September 2019

3. Climate of Central Greenland
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Climate of Central Greenland
during the last 17‘000 years
Alley et
al. 1993 YD
Holocene
Last 11‘700 years
4. September 2019

4. The classical subdivision by Blytt-
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The classical subdivision by Blytt-
Sernander (Mangerud et al. 1974)
yr BP
„Preboreal“ and „Boreal“ chronozones
High Northern Hemisphere (NH)
summer insolation
Temperate, large continental ice sheets start to melt
8500-5/6000 yr BP
„Atlantic“ chronozone“, „Holocene Clim. Optim.“, „Hypsi- or „Altithermal“
NH summer in-
solation starts to decrease, ITCZ moves south
Strong sea level rise, reduced Arctic sea ice cover (?)
5/6000 yr BP – Preind.
„Subboreal“ and „Sub-
atlantic“ chronozones,
„Neoglacial“
Low values of
NH summer
insolation
Sea ice increa-
ses, selected
glaciers grow
4. September 2019

5. Last 6000 years: Global over- view on 17 selected timeseries
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Last 6000 years: Global over-
view on 17 selected timeseries
Fig. 3. Holocene glacier variations (horizontal scale is schematic, not to scale) of Norwegian glaciers/glacier regions [Northern Folgefonna (Bakke et al., 2005a,b), Hardangerjøkulen (Dahl and Nesje, 1994, 1996), Grovabreen (Seierstad et al., 2002) Jostedalsbreen (Nesje et al., 2001), Spørteggbreen (Nesje et al., 2006), southeastern Jotunheimen (Lie et al., 2004), western Jotunheimen (Karlén and Matthews, 1992; Matthews and Karlén, 1992), northern Jotunheimen (Matthews et al., 2000, 2005), Snøhetta massif, Dovre (Dahl et al., in prep.), and Lyngen, Troms (Bakke et al., 2005c)]. For location, see Figs. 1 and 2.
Wanner et al. 2008
4. September 2019

6. Holocene: Dynamical structure
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Holocene: Dynamical structure
Neoglacial
cooling
period
Warm
Holoce-
ne cli-
mate op-
timum
Temperate
NH ice
caps melt
4. September 2019

7. (quasi-equilibrium simul., orbital, GHGs, ice sheets
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JJAS SAT / precip.:
6000 ka BP – preind.
(quasi-equilibrium simul.,
orbital, GHGs, ice sheets
specified)
Braconnot et al. 2007
4. September 2019

8. Now the mysteries Holocene climate change 4. September 2019
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Holocene climate change
Now the mysteries
4. September 2019

9. When did rapid climate changes occur?
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Holocene climate change
When did rapid climate changes occur?
4. September 2019

10. Summer temperature anomalies N America: Rapid climate changes
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Summer temperature anomalies N America: Rapid climate changes
Viau et al. 2006
Viau et al 2006
4. September 2019

11. Change Point Analysis: West Pacific
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Change Point Analysis: West Pacific
4. September 2019

12. ? Change Point Analysis: Global Distribution Grob 2009
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Change Point Analysis: Global Distribution ?
Grob 2009
4. September 2019

13. Holocene cold relapses?
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Holocene climate change
What do we know about
Holocene cold relapses?
4. September 2019

14. Glacier dynamics during the last 6000 years: Cycles exist!
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Glacier dynamics
during the last
6000 years:
Cycles exist!
Wanner et al. 2008
4. September 2019

15. Analysis of cold relapses
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Analysis of cold relapses
4. September 2019

16. Cold relapses. Overview
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Cold relapses. Overview
Bond
cycles 10 8 6 4 2
Wanner et al., in prep.
4. September 2019

17. 8200 yr event Wanner et al., in prep. 4. September 2019
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8200 yr event
Wanner et
al., in prep.
4. September 2019

18. Little Ice Age Wanner et al., in prep. 4. September 2019
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Little Ice Age
Wanner et
al., in prep.
4. September 2019

19. Medieval climate anomaly
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Medieval climate anomaly
Wanner et
al., in prep.
4. September 2019

20. Holocene climate change
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Holocene climate change
What was the influence of
the internal variability, mainly
▪ ENSO
▪ North Atlantic Oscillation
4. September 2019

21. ENSO frequency Wanner et al. 2008 Rein et al. 2004 Clement et al. 2000
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ENSO frequency
Rein et al. 2004
Clement et al. 2000
Wanner et al. 2008
4. September 2019

22. - - ? NAO frequency + Model 6000 – preind. Wanner et al. 2008
IMSC11 Edinburgh 2010 -
Rimbu et al. 2003 ? +
NAO frequency
Model 6000 – preind. -
Wanner et al. 2008
4. September 2019

23. A few conclusions Holocene climate change 4. September 2019
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Holocene climate change
A few conclusions
4. September 2019

24. Millennial scale: Overview (preindustrial – 6000 yr BP)
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Millennial scale: Overview
(preindustrial – 6000 yr BP)
Wanner et al. 2008
4. September 2019

25. Cycles, rapid changes (e.g., Bond)
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Cycles, rapid changes (e.g., Bond) ?
~1470 yr cycle
Fig. 3. Holocene glacier variations (horizontal scale is schematic, not to scale) of Norwegian glaciers/glacier regions [Northern Folgefonna (Bakke et al., 2005a,b), Hardangerjøkulen (Dahl and Nesje, 1994, 1996), Grovabreen (Seierstad et al., 2002) Jostedalsbreen (Nesje et al., 2001), Spørteggbreen (Nesje et al., 2006), southeastern Jotunheimen (Lie et al., 2004), western Jotunheimen (Karlén and Matthews, 1992; Matthews and Karlén, 1992), northern Jotunheimen (Matthews et al., 2000, 2005), Snøhetta massif, Dovre (Dahl et al., in prep.), and Lyngen, Troms (Bakke et al., 2005c)]. For location, see Figs. 1 and 2.
Bond et al. 2001: „A prominent feature of the North Atlantic‘s Holocene cli- mate is a series of shifts in ocean surface hydrography during which drift ice and cooler surface waters in the Nordic and Labrador Seas were repeatedly advected southward and eastward, each time penetrating deep into the war- mer strands of the subpolar circulation.“
4. September 2019

26. Does the actual anthropo- prevent a Little Ice Age?
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CO2, CH4 and N2 variations (6000 years)
Does the actual anthropo-
genic climate change
prevent a Little Ice Age?
Wanner er al. 2008
4. September 2019

27. Thank you! Holocene climate change 4. September 2019
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Holocene climate change
Thank
you!
4. September 2019

28. mid-Holocene climate mode
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A possible multi-century scale
mid-Holocene climate mode ? ?
Intermittent system!
4. September 2019

29. Holocene glacier advances
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Holocene glacier advances
Wanner et
al., in prep.
4. September 2019

30. Holocene climate change
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Holocene climate change
A few conclusions
▪ At the millennial scale the summertime cooling of the NH led to a
southern ITCZ shift, a weakening of the NH monsoon systems, and
lower SSTs in the North Atlantic area.
▪ At the decadal to multicentury scale evidence for quasiperiodic
fluctuations or oscillations exist. They were likely synchronous in
the North Atlantic area. Some cold relapses (e.g. the Little Ice Age)
were probably global phenomena.
▪ Several processes are postulated, but no single process or theory
might be responsible. Examples migth be: Meltwater flux in case of
the 8.2 kyr event, high volcanic and low solar activity during the
Little Ice Age. To accept: Climate system reacts in an intermittent
manner!
▪ In any case the growth and retreat of Arctic sea ice and the
dynamics of the MOC might have played an important role.
4. September 2019

31. Laurentide ice sheet, sea level
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A more dynamical view:
Laurentide ice sheet, sea level
LIS topography 9 kyr BP
Sea ice dynamics?
Fleming et al. 2000,
Milne et al. 2005
Carlson et al. 2008
4. September 2019