7.1 - Natural Causes of Climate Variations Flashcards
How does the PTSC contribute to natural variations in climate?
The PTSC creates icehouse and greenhouse climates on a timescale of hundreds of millions of years. When continents amalgamate to form a supercontinent, CO2 is removed from the atmosphere by rock weathering, particularly in mountains formed by continental convergence. Ocean basins deepen, leading to sea levels falling and as such, land surface area is increased as well as the albedo*. This results in a colder climate and the presence of ice sheets. On the other hand, supercontinent break-up generates greenhouse conditions because increased volcanic activity adds Co2 to the atmosphere and enhances the natural greenhouse effect. Other factors creating hothouse conditions include lower albedo due to increased sea levels and thus reduced land surface area.
How do LIPs contribute to natural variations in climate?
Large igneous provinces are extensive accumulations of intrusive and effusive igneous rocks that are emplaced over a geologically short duration. The Deccan Traps erupted at the end of the Cretaceous (ACDC) and the Siberian Traps erupted at the end of the Permian (selfish prat idk). These massive volcanic eruptions occurred over millions of years, releasing large volumes of greenhouse gases into the atmosphere. Additionally, the contact metamorphism in rocks (such as those rich in carbonates) surrounding the dykes liberated massive volumes of greenhouse gases into the atmosphere. This caused global temperatures to increase.
How do changes in the earth’s orbit contribute to natural variations in climate?
Earth’s climate depends on the amount and distribution of solar radiation the planet receives. Orbital eccentricity, obliquity and precession are 3 aspects of Earth’s orbital behaviour which influence the amount of radiation Earth receives and affects climate. The Milankovitch Cycles describe the collective effects of these changes in the Earth’s movements on its climate over tens of thousands to hundreds of thousands of years.
How does orbital eccentricity influence climate?
Orbital eccentricity refers to the deviation of Earth’s orbit from a circle. At the perihelion (ie. the point where Earth is closest to the sun), there will be more solar radiation reaching the Earth’s surface. At the aphelion (ie. furthest point), there will be less solar radiation reaching the Earth’s surface. However, eccentricity only causes small variations in this when relative to the effect of Earth’s tilt.
How does obliquity (Earth’s tilt) influence climate?
The angle of Earth’s rotational axis affects climate. It creates seasons in higher latitudes with summer occurring when the axis is oriented towards the Sun and winter occurring when the axis is oriented away from the Sun. At the greatest tilt, more solar radiation reaches Earth’s surface in summer and less reaches it in winter meaning that seasons become more extreme. At present, the tilt is gradually declining, which should result in milder summers and winters as well as gradual cooling
How does precession (the oscillation of the Earth’s rotational axis) influence climate?
Precession affects climate in combination with orbital eccentricity. If the rotational axis of a hemisphere is pointing towards the Sun at perihelion, seasons become more extreme in terms of the solar radiation the hemisphere receives
Explain how a change in ocean circulation may affect Earth’s climate
Ocean water currents transport heat from the equator to the poles which affects the water cycle as well as atmospheric temperatures. Increased ocean circulation warms the higher latitudes of both the northern and southern hemispheres. Flow-on effects of this include high evaporation rates over oceans and associated increases in precipitation events. Similarly, a reduction in ocean circulation from the equator to the poles will reduce temperatures, possibly producing a prolonged cooling event.
How does continental drift due to plate tectonics affect the nature of ocean currents?
Continental motion changes the sizes and locations of both land masses and ice caps. Continents can also act as barriers or can form new seaways. This in turn alters ocean circulation patterns, which are responsible for transporting heat around the earth. Flow-on effects include changed atmospheric circulation processes as well as changes in precipitation patterns.
Eg. The Gulf Stream is a current moving along the east coast of NA that transports heat and moisture towards the north.
