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Global overturning circulation – distributing heat and carbon on centennial to millennial timescales

Christo Buizert

Kathleen Wendt

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Global Overturning Circulation

Talley 2013

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Global circulation – the 3D view

Talley 2013

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The Atlantic Meridional Overturning Circulation

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In Hollywood:

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Dansgaard Oeschger Events

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Atlantic Meridional Overturning Circulation

[Rahmstorf 2002]

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Dansgaard Oeschger Events

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Global ocean temperature

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Global Ocean Temperature oscillations

Time

Greenland / N-Atlantic

Antarctica / Mean Ocean Temperature

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Energy flow

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Energy flow part 2

DO event energy balance

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DO warm minus DO cold

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Energy flow part 2

Southern Ocean energy balance

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SO warm minus SO cold

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Can models capture this? – YES!

Planktic

Benthic

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What about the carbon cycle?

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Heinrich Events

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Heinrich Events – CO2 release from the oceans

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Kathleen Wendt PNAS cover

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Questions?

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Methane

Debriefing the methane lab activity, discuss rate of change

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Step 1: Gas extraction

  • How do we ensure we don’t contaminate sample with lab air?
  • What other types of extraction exist?

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Step 2: Gas chromatography

  • How does a gas chromatograph work?
  • How do we calculate a concentration?

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Step 2: Gas chromatography

  • How does a gas chromatograph work?
  • How do we calculate a concentration?

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Step 3: Sample analysis

Sample

Pressure (torr)

Peak Area

Methane concentration

SDMF (91 m)

First expansion

 

 

 

SDMF (91 m)

Second expansion

 

 

 

SDMF (93 m)

First expansion

 

 

 

SDMF (93 m)

Second expansion

 

 

 

SDMF (95 m)

First expansion

 

 

 

SDMF (95 m)

Second expansion

 

 

 

  • What concentrations did we get?
  • How do we calculate precision?
  • What are some corrections we make to the measurement?

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Step 4: Determining sample age

  • What ages did you assign for yesterday’s samples?
  • What are other methods for determining the chronology of a paleo record?

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Calculating a rate of change

Period

Approximate CH4 concentration (ppb)

Rate of change (ppb/yr)

Early part of modern rise (average of today’s samples)

 

 

Late Holocene (latest data point at 36 years before 1950)

 

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Methane cycle

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Methane pause

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Recent ice core evidence

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Your results from yesterday’s exercise