Cryosphere

The cryosphere deals with all forms of frozen water (where water is solid form). This varies from ice sheets to snow to permafrost. The cryosphere is a delicate and specialised sphere as it is very dependent on temperature therefore in some places it is seasonal yet in others it is continuous. It is the only sphere where in areas it can disappear and reappear and is most likely to fail than any of the others due to rising temperature.

Figure 1 Cryosphere areas (Retireved from: http://www.nasa.gov/vision/earth/features/bmng_gallery_3.html Date 16/9/2015)

The cryosphere covers different areas of the planet with respect to the optimal climate for which water will freeze as this process is weather and temperature dependent. Therefore many of the places in which water freezes are of low latitude or high topography Fig 1. As these two qualities have the ideal climatic conditions for water to freeze. 

So how does water freeze?

Figure 2 hydrogen bonding (Retieved from: http://philschatz.com/anatomy-book/contents/m46000.html Date 16/9/2015)

Water is comprised of H₂O molecules (oxygen and hydrogen molecules bonded together) which in liquid form have a relative high energy in relation to the temperature of the molecules (NB temperature and heat energy are related). When this energy is removed (transferred into another energy state), the water molecules start to come together, eventually at 0° water molecules get close enough that they start to bond to each other, as the hydrogen and oxygen atoms are attracted to the opposite charge of the other atom  forming a hydrogen bond Fig 2.

By doing this water molecules bond together in a hexagonal shape forming a solid structure, known as an ice crystal (NB snow is formed of ice crystals yet is different to ice as it forms from water vapour and undergoes reverse sublimation, therefore it skips the slowly coming together phase).

Therefore the cryosphere will form in an area where temperature is low so that water molecules will lose their heat energy and be able to undergo hydrogen bonding to form a solid state.

How did the Earth form ice caps and frozen regions (large scale freezing)?

The Earth has had ice caps for a short period of time in comparison with how long it has been around. This is due to the Earth’s natural increase and decrease in temperature due to geological events. The modern ice caps we have today (Arctic and Antarctic ice caps) formed due to two separate plate tectonic events.

1.    Antarctic Ice Cap: Antarctica, New Zealand, Australia and South America were once joined together to form Insert name of continent Gondwana. When the respective landmasses rifted apart leaving Antarctica alone, an ocean current was able to flow around the continent uninterrupted (the Antarctica circum-polar current). This affected the Earth’s overall ocean currents as it diverted warm currents from the equator away from the continent. This resulted in an overall decrease in temperature for the continent, enough so that water was able to freeze and form the Antarctic ice sheet.

2.    Arctic Ice Cap and Greenland Ice sheet. The closing of the panama sea way from the joining of the North and South America continents, diverted the warm water from the pacific to entering into the, cooler waters of the Atlantic ocean. This caused an overall drop in temperature in the Atlantic which resulted in a climatic cooling and the formation of the Arctic Ice cap and Greenland ice sheet.

Temperature vs age of the Earth (Dr Travis Horton, powerpoint slides, 9th September 2014).

From Fig3 it is evident that the Earth has been in multiple ice ages, which leads to the question; how did the ice age end if humans weren't there to contribute to global warming?

This is an interesting point as global warming is a naturally occurring event, due to the Earth system being dynamic and one event generates a change in another sphere.

This is evident with the geosphere driving tectonic events creating an increase in the amount of CO₂ and methane, resulting in an increase in the temperature of the Earth. This is due to the insulating properties of Carbon Dioxide, from volcanic events and the release of methane, from methane clathrates.

Naturally occurring carbon dioxide is produced from the Wilson cycle, a process of opening and closing of a basin (typically ocean basin), a process that  creates and removes CO₂ Fig4.

Figure 4 Wilson cycle ( Retieved from: https://classconnection.s3.amazonaws.com/483/flashcards/684483/jpg/wilson_cycle-143EAF5CF0127F11BB5.jpg Date 19/9/2015).

Carbon dioxide is realised into the atmosphere where it reacts with water and calcium carbonate to form carbonic acid and calcium ions Eq1

Eq1: CO₂ +H₂O → H₂CO₃

The carbonic acid then reacts with the feldpars within grantie rocks to form clay minr=erals and by product ions Eq2.

Eq2: 2NaAlSi₃O₈ + 2H₂CO₃ + 9H₂O → Al₂Si₂O₅(OH)₄ + 4H₄SiO₄ + 2Na⁺ + 2HCO₃^-

The bicarbonate ions then react with liberated calcium ions to form calcium carbonate, carbon dioxide and water Eq3.

Ca₂⁺ +2HCO₃⁻ → CaCO₃ + CO₂ +H₂O

(http://www.columbia.edu/~vjd1/carbon.htmlRetrieved 19/9/2015)

Other contributing factors are; an over drive in CO₂ reduction, plate tectonics or the Earth’s position relative to the sun, can all have a cooling effect on the Earth and send it into an ice age.

From Fig3 it is evident that the earth has a natural heating and cooling cycle and that given millions of years it eventually returns to a climatic optimum for a brief period of time. Since the Earth is coming out of an ice age at present, from the release of natural methane clathrates, it is of importance to think; “what will be the consequence of adding human driven increase in greenhouse gases?”

Human addition of greenhouse gases has increased the natural global warming cycle beyond the point of which the Earth can counter itself. This means that it is going to require human intervention to reduce the rate at which this is occurring, as the natural cycle requires million plus years to counter this.

However we can’t reverse what we have done, which means we need to adjust the way we live to suit to the environment and climatic changes that are occurring. It also means that we need to understand that some forms of biological life won’t be able to cope with the rapid changes and may extinct. Due to all forms of biological life being the optimal form of life that organism can be at this point in time in relation to its surrounding environment, as it has evolved to be suited to it.