Chapter 11 - Orbital Scale Changes in CO2 and Methane Flashcards

1
Q

Why are steep edges avoided when drilling ice cores?

A

As ice here flows quickly to margins and melts

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2
Q

When does CO2 dissolve more readily?

A

In cold seawater. This would lower atmospheric levels.
This was offset by higher salinity in high latitude oceans thus net drop of atmospheric CO2 was 14ppm

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3
Q

Where does high productivity occur?

A
  1. Coastal areas - due to rivers and upwelling
  2. Narrow regions of upwelling near equator
    High latitudes
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4
Q

Why do methane minima not match insolation minima amplitudes?

A

This is because some wetlands persist through extreme drying, most likely near the equator. Also, emergence of Australian wetlands when SL drops during minima

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5
Q

How are ice cores dated?

A

By counting annual rings, carrying out the ice flow model or dating air bubbles trapped by sintering.

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6
Q

Why are air bubbles in ice cores younger than the ice in which they are sealed?

A

Air bubbles are older than the overlying atmosphere but younger than the ice in which they are trapped as the ice was deposited many years prior. Difference in age depends on rate of deposition (fast deposition, small age gap)

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7
Q

To what extent does a cooler glacial ocean explain lower CO2 in the glacial atmosphere?

A

Not particularly well; although cooler ocean temperatures would allow co2 to more easily dissolve, thus removing it from the atmosphere, this is offset by increased salinity. Ocean salinity increased during glacial periods due to salt rejection.

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8
Q

Where did the carbon removed from the atmosphere go during glaciation?

A

Carbon was stored in the deep ocean. Enhanced carbon pumping increased deep ocean co2 levels by 2.7%. This value comprises all missing atmospheric carbon however is little in comparison to the large amount already stored here.

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9
Q

What effect does fractionation have on carbon isotope values?

A

Fractionation occurring during photosynthesis increases 13C values in surface waters as inorganic carbon is converted to organic carbon, and plants more easily incorporate 12C to their tissues. This discrimination causes enrichment of 12C in organic matter.

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10
Q

Explain how carbon isotope changes trace shifts of carbon from land to ocean?

A

An increase of carbon from land to ocean would bring an influx of 12C, thus reducing 13C levels. Comparing isotope concentrations will evidence land-brought carbon

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11
Q

How does the oceanic carbon pump reduce co2 levels in the atmosphere?

A

The carbon pump refers to the situation of inorganic carbon in surface water sinking to the deep ocean following photosynthesis. A reduced concentration of carbon in surface waters means it cannot escape to the atmosphere. Furthermore, carbon which has sunk can be converted to CO3-2, which rises to the surface and draws down co2 to from the bicarbonate ion

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12
Q

What evidence indicates a different glacial deep-water flow pattern in the N Atlantic?

A

Positive 13C values are observed in the North Atlantic while low values are seen in the South Pacific. Water flows from these regions combine in the equatorial Atlantic seafloor; relative contributions of each flow can be determined by isotope concentration

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13
Q

How could a change in deep water circulation in the Atlantic ocean alter atmospheric CO2?

A

Intermediate waters could deliver more nutrients to the surface, thus increasing carbon pumping. Furthermore there could be increased bicarbonate ion concentration

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14
Q

What characteristics of 18O and greenhouse gas records tell us if gases act as ice sheet forcing or feedback?

A

Gases act as a forcing at the 23,000 cycle and feedback at 41,000 cycle

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