Geography Homework: Analyzing Climate Change and Carbon Cycling

This Geography assignment delves into several key environmental science topics. It begins by comparing the atmospheric conditions of Venus and Mars in relation to solar luminosity and carbon cycling. It then discusses how the carbon cycle adjusts to changes in solar luminosity and human activities. The assignment further explores the use of carbon-14 as a tracer in oceanic processes, detailing its role in deepwater formation, upwelling, and the biological pump. Finally, it examines the hydrological impacts of deforestation, including changes in water flow, nutrient runoff, soil characteristics, and mineral concentrations in streams, and also the impact on Sulphur assimilation. Desklib offers a wealth of similar assignments and resources for students seeking to deepen their understanding of environmental science.

Geography
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Question 2
a) It is suggested that the planet Venus had oceans and a different atmosphere (from the
present atmosphere) billion years ago. Over time the solar luminosity increased
gradually which in turn released huge volumes of carbon from the mantle to the
atmosphere. Also, it caused water to evaporate from the oceans to cause a runaway
greenhouse effect. Oceans evaporated into space and the atmosphere was turned into
carbon dioxide. In addition, volcanic eruptions released carbon into the atmosphere
which also contributed to the runaway greenhouse effect. The huge amount of carbon
dioxide in the Venus atmosphere is responsible for maintaining the high temperatures.
Mars is further away from the sun hence experiences reduced solar luminosity. For
this reason, there is minimal evaporation in the atmosphere and most of the carbon are
trapped in the Mars’s mantle. The result is a thinner atmosphere which is not able to
trap a lot of solar energy. The volcanic activities are responsible for releasing
greenhouse gases into the atmosphere but there are not very frequent hence the
surface of Mars remains relatively cold.
Carbon dioxide is a greenhouse gas that plays a major role in warming the atmosphere
by trapping the suns energy radiated from the earth’s surface. The primary source of
the gas is the outgassing from the interior of the earth along the mid-ocean ridges and
volcanoes. Most of this carbon is absorbed by the ocean, some stored as biomass in
organisms while some retained by carbonate rocks. Processes such as photosynthesis,
respiration, weathering and metamorphism of carbonates regulate the carbon dioxide
to moderate the earth’s climate.
b) The carbon cycle can adjust for instance increased rate of photosynthesis because of
increased solar luminosity reduces the amount of carbon dioxide in the atmosphere.
This moderates the effect of increased luminosity on the earth's climate. On the other
hand, reduced solar luminosity might be moderated by human activities such as
industrialisation which releases more carbon into the atmosphere. The carbon in
return traps more sunlight energy and hence moderate the earth’s temperature despite
the reduced solar luminosity1.
Question 3
a. Carbon 14 is a natural radionuclide present in the ocean and can be used as a tracer of
the oceanic processes. By application of isotopic techniques, the carbon 14 can be

useful in understanding sources, dynamics, pathways and fate of carbon in the ocean
once it enters from land or the atmosphere.
b. The three processes that is; Deepwater formation, upwelling and the biological pump
are responsible for the level of carbon 14 in the atmosphere. These processes are
responsible for the absorption of carbon from the atmosphere as well as its
distribution within the ocean waters.
c. The oceanic carbon 14 distribution is incorporated within the shells of benthic
foraminifera. These are preserved in the sediments within the Deepwater. As plants
and organisms’ debris decompose into the Deepwater the carbon 14 is removed from
the surface water and deposited in the Deepwater.
d. The upwelling process has a significant influence on the atmosphere. Since the
upwelled water replaces ocean surface water continuously, it’s responsible for the
absorption of a huge amount of excess carbon 14 from the atmosphere.
e. A complex mix of biological and physical processes assist in the transfer of carbon 14
from the oceanic photic zones to the deep waters as well as the seafloor. Due to the
biological pump effect nutrient concentration are depleted from the surface waters
experiencing net photosynthesis. Instead its elevated at a depth where net respiration
is experienced. The biological pump and oceanic circulation experience an interplay
which in turn dissolve inorganic carbon into the ocean.
Question 4
a) The clearance of forests will have a hydrological impact, one such effect will be the
amount of water which will be allowed to flow down the streams. Trees reduce the
rate of water flow hence giving time for more water to infiltrate into the soil.
Cutting down of trees kills its roots. The roots of the plant are responsible for
anchoring nitrogen in the soil hence when they die the nutrients are free to move with
runoffs. Considering that the nutrients are no longer being absorbed by the trees more
nitrogen will be added into the waterways.
Since trees are responsible for controlling soil erosion cutting them down will mean
soil can now be easily carried away by the flowing water. The result on the soil
characteristic will be reduced soil nutrient as much of it will be carried by the flowing
water. Also, the soil itself is ferried to the oceans leaving the ground with rocks which
cannot support vegetation. Furthermore, clearing of trees increases the magnitude of
solar radiations hitting the soil which in turn increases soil temperatures.

b) The high flow of Nitrates into the water system was caused by the death of plants
roots which initially anchored them into the soil. The lack of nitrogen absorption by
the trees also added to the volume of nitrates which were freely ferried by the running
water.
c) The cutting of trees reduces the rate of nutrients uptake and instead accelerates
runoffs. Also, the soil temperature will increase to fasten mineralization and the
nitrification process in the soil. This will lead to the release of the cations into the
water streams. The resulting effect will be a high concentration of the minerals in the
stream water2.
d) The death of trees minimises sulphur assimilation hence the amount of sulphate
released to the atmosphere reduces.

References
1. Pidwirny, Michael (2006). Fundamentals of Physical Geography: 2nd Edition
2. Kreutzweiser DP, Hazlett PW, Gunn JM. Logging impacts on the biogeochemistry of
boreal forest soils and nutrient export to aquatic systems: A review. Environmental
Reviews. 2008; 16:157–179