Heinrich Events:

1
Heinrich Events

• Massive late pleistocene detritus layers of the
  North Atlantic and their global climate imprint.

- Sidney R. Hemming
2
How to spot a Heinrich event

• Hartmut Heinrich (1988)
• High lithic percentages
• Ratio of lithic to total grains in 180micron-3mm
  fraction
• Abrupt change
• High detrital carbonate in correlative intervals

http//www.ncdc.noaa.gov/paleo/slides/slideset/ind
ex19.htm
3
When and where?
4
When (again)?
S.R Hemming, 2004

• 7Kyr intervals
• 500yrs duration
• H0?

5
Geological provenance

• Where does the IRD originate?
• Used K/Ar, Nd, Sm, and Pb isotopes
• Organic geochemistry
• Originate near the Hudson Strait
• H3 and H6 from elsewhere?
• H3 and H6 low foram intervals rather than ice
  rafting.

6

• Surface and deep water changes

Ahhh the Heinrich events.I remember them
well. There was a drop in T and S in the IRD
belts, I was living there at the time. Maslin et
al said my dO18 dropped up to 2 permil!
Miss N. pachyderma
7
Surface and deep water changes

• Dinoflagellate low salinity and sea ice around
  margins of N Atlantic.
• But sea ice free Nordic seas at LGM
• Heinrich 10month sea ice cover and sea surface
  salinity decrease further.
• Lower dO18 transferred to deep ocean brine
  rejection.

8
Surface and deep water changes

• Changes in NADW
• Dramatic reduction proposed based on dC13 of
  benthic forams
• Changes in thermohaline circulation could be
  trigger for abrupt climate change.

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At the same time.

• Correlate with Heinrich events, most thought to
  be wind related.
• Stronger trade winds in tropics
• Stronger winter monsoon winds in China and
  Arabian sea
• Stronger Northerly winds in W Med.

10
Mechanisms

• 3 proposed mechanisms
• - Catastrophic ice sheet purging
• - Jokulhlaup activity
• - Ice sheet build up/collapse

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MacAyeal (1993) and the Binge Purge Model

• Large Ice sheet builds up gradually binge
  dependent on air and moisture supply.
• Combination of geothermal heat, advection of heat
  from surface, internal friction..
• Destablises rapid purge phase or heinrich
  events.
• Alternative ice load induced earthquakes,
  timing?

12
MacAyeal (1993) and the Binge Purge Model

• Binge model has interval 7kyrs
• Very close to Heinrich timing.
• 1.25x106km3 freshwater -gt 3.5m sea level rise

13
Johnson and Lauritzen (1995) in an adventure with
the Jökulhlaups
Definition 1 Jökulhlaup is a hard-to-pronounce
Icelandic word meaning glacier burst English
speakers say it "yokel-lowp" and people from
Iceland know what we mean.

• Definition 2 (possibly more useful)
• A jökulhlaup is a massive flood that occurs
  when the height of a dam is exceeded by lake
  level because of the rising lake level or reduced
  flow of glacial ice into the dam

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Johnson and Lauritzen (1995) in an adventure with
the Jokulhlaups

• Repetative Jökulhlaups freshwater pulses into N
  Atlantic when Ice dams at mouth of Hudson Strait
  failed.
• Very rapid
• Accounts for precusor fine carbonate near hudson
  strait brought by meltwater not icebergs
• Sea level change 0.2m, instantaneous.
• Propose Hudson Bay is filled with water,
  surounded by ice flowing into it.
• Early phases of ice sheet build up possible,
  but
• LGM unlikely
• Large lakes under ice sheet? meltwater plus
  destabilisation of ice sheet (J. Andrews)

15
The model of Hulbe (1997)

• Hudson Strait ice flows from Hudson Bay dome into
  Labrador sea.
• Operate under extreme cold
• Grounded ice flows into sea and floats forming
  ice shelves
• Sediment enriched in basal ice sheets by basal
  freezing due to large slopes in basal topography.
• BUT, not Heinrich event for every cold interval
  in Greenland.
• BUT, they do occupy long cold intervals time
  for ice sheet to build up? (1000yrs cooling)
• No, or little sea level rise.

16
Hulbe revises his model, 2004

• Fringing ice sheet margin
• Not extending across Labrador sea
• Events due to explosive disintegration of ice
  shelf.

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Conclusions

• Abrupt climatic events freshwater input and
  large deposits of IRD in N Atlantic.
• Occurred during cold periods in N. Atlantic, and
  followed by abrupt warming.
• IRD due to ice armadas from Laurentide ice
  sheet through Hudson Strait. 3 Mechanisms.
• Freshwater input decreases (shuts down?) NADW.
• Coincident with other climatic changes seen
  elsewhere in the world.
• Further work to see if global or N. Hemisphere
  wide events.