1. The Origin of the Atmosphere
Intro to Atmospheric Physics
08/26/15
Dr. Chris Moore

2.
Atmosphaerenphysik/WS1011/01_Physics_of_the_Atm-WS2010_Intro_tl.pdf

3. How did our atmosphere develop?

4. Geologic time scales
Understanding the evolution of the atmosphere involves looking at the development of Earth and planets in general
The development of the Earth’s atmosphere is still a hot topic of research with new breakthroughs happening all the time
There are two processes governing the development of Earth and the early atmosphere:
1) Accretion
2) Outgassing

5. Accretion
Earth formed from the Solar Nebula (swirling disk of interstellar dust and hydrogen surrounding the earliest form of the sun) about 4.6 billion years ago
Iron and nickel core forms first due to cooling and they solidify at the highest temperature
Then continued collisions and differentiation separates areas due to different densities

6. Outgassing Process where gases trapped in interior get released
Early oceans of hot magma existed on the surface overturning planetary material
Volatile gases released from interior
CO2 CO H2 N2
H2O
Gases remained trapped in a surface layer by gravity
Still occurs today through volcano eruptions
Following accretion into a large planet-sized object during the early years of the solar system, Earth’s first major atmosphere was formed by the release of gases trapped in the restless interior, a process that still goes on today in volcanoes (Figure 8.1). These early years are marked by swirling oceans of hot magma that no longer exists today on any planet in our solar system. Extreme volcanism in Earth’s early history occurred in response to this energetic motion of then-molten mantle material. As planetary material violently overturned, volatile gases from the interior, especially Carbon dioxide (CO2), Carbon monoxide (CO), Hydrogen (H2), Nitrogen (N2) and water vapor (H2O), were released, and accumulated in a gaseous surface layer that was trapped by gravitational forces. Radiation from the nearby Sun swept lighter gases as H and He away, leaving only heavier molecules in this early atmosphere. Chemical reactions in the hot surface layer formed other simple atmospheric compounds, such as methane (CH4) and ammonia (NH3). While far less abundant, the latter compounds are highlighted as they are key components of amino acids, which are the fundamental building blocks of life’s proteins. Note also that Oxygen (O2), key to the survival of many forms of modern life, was not present in the early atmosphere.

7. Early Atmosphere The early atmosphere was devoid of oxygen (reducing)
There is still debate about when the current oxidizing atmospheric composition developed
Traditionally this was thought to have occurred around 400 million years ago driven entirely by O2 produced from photosynthetic activity

8. Recent developments
Atmosphere as we know it (oxidizing) may have actually started forming 4 billion years ago
This has large implications for our understanding of the development of life as the current understanding is that life developed during the reducing atmospheric conditions
Very interesting area of on-going research…

9. Evolution of Carbon

10. Biological Evolution
The evolution of the current atmosphere is strongly linked to the evolution of plants to produce the oxygen
13.2: Postulated rise in atmospheric oxygen over geologic time, and its relationship to ice ages (blue bars) and biospheric evolution. If the step-like rises in oxygen were rapid, consequent destruction of atmospheric methane (a powerful and potentially major greenhouse gas in the early atmosphere) could account for the Makganyene and Sturtian snowball earths. If the oxygen rises were slow (millions of years), methane destruction might be offset by CO2 rise modulated by silicate weathering feedback. The Marinoan snowball earth, coming <75 Myr after the Sturtian, is more difficult to attribute to methane destruction, requiring a methane-oxygen see-saw.

11.
studium/lehre/Atmosphaerenphysik/WS1011/
01_Physics_of_the_Atm-WS2010_Intro_tl.pdf

12.
studium/lehre/Atmosphaerenphysik/WS1011/
01_Physics_of_the_Atm-WS2010_Intro_tl.pdf

13. Atmospheric “Floors” Characteristic temperature profiles in the layers

15. Tropopause Can be defined by temperature changes
Can also be defined chemically
Lower stratosphere has higher ozone and lower water vapor

16. hectopascal A

19. Atmospheric Pressures
It is often easiest to represent the atmosphere via pressure (isobaric) to make equations either to deal
Therefore, it’s good to get used to the approximate pressures at different heights

20. Atmospheric Chemistry

24. No. of Different Species

27. Hg biogeochemical cycle
From

28. Mercury in the Arctic Fragile Arctic ecosystems
Methyl mercury is a neurotoxic pollutant and accumulates in living organisms
Piscivorous fish
Polar Bears
Whales
Seals
Muktuk
Valera et al NeuroToxicology; Tian et al Environment International

29. Mercury and Ozone in the Arctic
Surface Layer
From Steffen et al ACP

30. Quiz!
Thanks to Thomas Leisner at IUP (Institute of Environmental Physics) Heidelberg for the many slides