Reference Figures for Essay Questions – Do not write on these and hand in for reuse!
Q60: Tropical rainforest locations and the biogeochemical cycle
Figure 1: Present and original extent of humid tropical forest
The boundary between forest and non-forest (savannah) follows the 1500 mm rainfall line.
Figure 5: Nutrient budget in a tropical forest
Figure 5 shows a budget accounting that indicates nutrients are found mainly in living plant
biomass and in the layer of decomposing litter; there is little nutrient content of the deeper
soil, as there is in temperate-zone ecosystems. This suggests that plants are intercepting
and taking up nutrients the moment they are released by decomposition.
Q61. Volcanic Eruptions and Climate
Left: Reduced solar radiation due to volcanic aerosols as measured at Mauna Loa Observatory, Hawaii. Image
credit: NOAA/ESRL.
Right:. An 18 km-high volcanic plume from one of a series of explosive eruptions of Mount Pinatubo beginning on 12
June 1991, viewed from Clark Air Base (about 20 km east of the volcano). Three days later, the most powerful
eruption produced a plume that rose nearly 40 km, penetrating well into the stratosphere. Pinatubo's sulfur emissions
cooled the Earth by about 1°F (0.5°C) for 1 - 2 years. (Photograph by David H. Harlow, USGS.)
Annual near-surface temperature anomalies for the year following a mega-colossal volcanic eruption like the Toba
eruption of 74,000 years ago, if it were to occur today. Most land areas cool by 22°F (12°C) compared to average.
Some areas, like Africa, cool by 29°F (16°C). Image credit: Jones, G.S., et al., 2005, "An AOGCM simulation of the
climate response to a volcanic super-eruption", Climate Dynamics, 25, Numbers 7-8, pp 725-738, December, 2005.
Volcanos can also act to warm the climate over longer time scales, since they are an important source of natural CO2
to the atmosphere. It would take ~11,700 extra Kilaueas to equal industrial output though! Kerrich 2001). Q60.
Q62 Structure of the Atmosphere and Greenhouse Heating Effects
The Troposphere starts at the ground or sea and reaches up to 10 - 12 km
height. Physically it is characterized by a continuous decrease of temperature
with increasing height. The height of the tropopause is very dependent on
geographical latitude and season with a maxmum height in tropical regions. At
the polar regions, the tropopause is located at about 8 km height. The
troposphere contains about 80 % of the mass of the atmosphere and also
contains almost all of water of the atmosphere. In it's lowest layer of about 1 to
2.5 km, the planetray boundary layer (PBL), the influence of Earth's surface
causes heavy variances of meteorologic parameters like temperature, wind and
humidy. In the higher regions of the tropopause, temperature is about -60 °C.
At this heights, relatively small bands with very high wind speeds (up to
500 km/h), the jet streams, occur. Above the Mesopause the Thermosphere is
ionized to a plasma and being shed to space.
Q63 & General Background for Earth History and Climate
This clock representation shows some of the major units of geological time and definitive events
of Earth history. The Hadean eon represents the time before fossil record of life on Earth and
liquid oceans; its upper boundary is now regarded as 4.0 Ga.[1] Other subdivisions reflect the
evolution of life; the Archean (one celled life) and Proterozoic (>680 Ma, soft bodied animals)
are both eons, the Palaeozoic (complex hard bodied invertebrates, first land plants), Mesozoic
(Dinosaurs, birds, flowers, bees) and Cenozoic (angiosperms, mammals) are eras of the
Phanerozoic eon. The two million year Quaternary period, the time of recognizable humans, is
too small to be visible at this scale. Polar ice caps or snowball earth times are limited to:
Archean 2.3 Ga, Late Proterozoic 750-580 Ma, Mid-Ordovician, Permian, Neogene >4.6 Ma.
Notable hothouse times with high sea levels, vigorous carbon cycles and more atmospheric
oxygen, CO2 &H2O include Devonian, Cretaceous and the Paleocene-Eocene Thermal
Maximum.
Q63 continued - Orbital Variations
Left: The eccentricity of the Earth's orbit changes slowly over time from nearly zero to 0.07. As the orbit
gets more eccentric (oval) the difference between the distance from the Sun to the Earth at perihelion
(closest approach) and aphelion (furthest away) becomes greater and greater. Note that the Sun is not at
the center of the Earth's orbital ellipse, rather it is at one of focal points.
Right: The eccentricty of the orbit shown in the right image is a highly exaggerated 0.5. Even the
maximum eccentricity of the Earth's orbit—0.07—it would be impossible to show at the resolution of a
web page. Even so, at the current eccentricity of .017, the Earth is 5 million kilometers closer to Sun at
perihelion than at aphelion. (Images by Robert Simmon, NASA GSFC)
Left: The change in the tilt of the Earth's axis (obliquity) effects the magnitude of seasonal change. At
higher tilts the seasons are more extreme, and at lower tilts they are milder. The current axial tilt is 23.5°.
Image by Robert Simmon, NASA GSFC)
Left: Precession—the change in orientation of the Earth's rotational axis alters the orientation of the Earth
with respect to perihelion and aphelion. If a hemisphere is pointed towards the sun at perihelion, that
hemisphere will be pointing away at aphelion, and the difference in seasons will be more extreme.
Currently, northern summer occurs near aphelion. (Image by Robert Simmon, NASA GSFC)
Q64 - The Isotopic Composition of Seawater and Glacial Ice
Fractionation of heavy and light water by evaporation and condensation in the hydrologic cycle. Most water is:
1 16
H2 O with a mass of 18 g/mol. Small amounts of heavy hydrogen 2H (deuterium) and 18O give rise to water that
can be heavier with masses up to 20 g/mol. These components of heavier water evaporate last and condense or
crystallize first and diffuse more slowly than light water as the air that contains tem cools. (Illustration by Robert
Simmon, NASA GSFC)
This graph is empirical data from the isotopic composition of precipitation as a function of the temperature where
the precipitation fell. Note that negative values for delta 18O are depleted or too light. The horizontal temperature
scale goes from -60° like over Antarctica or Greenland to +20°C like in the tropics. (Graph adapted from Jouzel et.
al., 1994). Figure 4. Annual near-surface temperature anomalies for the year following a mega-colossal volcanic
eruption like the Toba eruption of 74,000 years ago, if it were to occur today. Most land areas cool by 22°F (12°C)
compared to average. Some areas, like Africa, cool by 29°F (16°C). Image credit: Jones, G.S., et al., 2005, "An
AOGCM simulation of the climate response to a volcanic super-eruption", Climate Dynamics, 25, Numbers 7-8, pp.