EQ1 Flashcards
What are the two dominant states that the planet’s climate fluctuates between, and what state are we currently in?
The greenhouse Earth and the icehouse state. The Earth is currently in an icehouse state due to there being some continental glaciers on the planet.
What does the climate fluctuate between during the icehouse stage?
During the icehouse stage, when large ice sheets are present on the Earth, the climate fluctuates between cooler glacials, when ice advances, and warmer interglacials, when ice retreats. The Earth is currently in an interglacial period of the icehouse climate stage.
What was the last glacial stage?
The Pleistocene epoch was the last time that the Earth’s climate was in a glacial stage, which lasted until around 12,000 years ago.
What is the current interglacial stage called?
The Holocene epoch is the current epoch which is in an interglacial period, which started around 10,000 years ago.
What are the fluctuations during each major glacial?
There are fluctuations within each major glacial. These relatively short-lived pulses of ice advance are known as stadia,s, and warmer periods of retreat known as interstadials.
What was the last glacial maximum?
The last glacial maximum is known as the Devensian, which occurred approximately 18,000 years ago.
What was the last glacial advance?
The last glacial advance is known as the Loch Lomond Stadial, which occurred between 12,000 and 10,000 years ago, marking the end of the Pleistocene epoch.
Long-term causes of climate change (8 marks):
Point 1 - Individually, the orbital variations of axial tilt, eccentricity and wobble have a limited impact on Earth’s weather but over a 100,000 year cycle these oscillations combine to
cause major temperature changes leading to dramatic variations in global ice volumes.
point 2 - In support of Milankovitch’s theory is the fact that glacials In support of Milankovitch’s theory is the fact that glacials seem to have occurred at regular intervals of approximately 100,000 years. However the actual impact of combined orbital changes on solar radiation amount and distribution is small, probably only enough to change global temperatures by between 0.5 and 1C.
Point 3 - To explain the larger temperature changes of up to 5C that were required for the vast expanses of ice to form, or alternatively melt, we have to look at climate feedback mechanisms. For example, once the Milankovitch cycle created a small fall in temperature of 1ºC, there would be a small increase of snow/ice, which raises surface albedo, leading to more solar energy being reflected back to space. this in turn decreases the temperature even more, creating a cycle of positive feedback.
What are two short term causes of climate change?
Volcanic eruptions and variations in solar output.
Explain how volcanic eruptions can cause short term climate change?
During volcanic eruptions, large amounts of ash is thrown into the atmosphere. Although, this all returns to the surface within a few months, limiting the effect on climate change. The most significant impact on climate change is the injection into the atmosphere of large quantities of sulphur dioxide gas. the gas remains in the atmosphere for as long as 3 years, during which it forms sulphate aerosols which increase the reflection of radiation from the sun back into space, cooling the Earth’ lower atmosphere.
Explain how variations in solar output can cause short term climate change?
On the face of the sun there are dark patches, called sunspots, which are caused by intense magnetic activity in the sun’s interior. an increase in the number of sunspots means that the sun is more active and giving off more energy. Therefore, sunspot numbers indicate levels of solar output, which appear to vary over an 11-year cycle, leading to changes in the climate over s short period of time.
Cause of the Loch Lomond Stadial:
One possibility was that the Loch Lomond stadia was triggered when drainage off the huge proglacial Lake Agassiz disrupted the THC (Thermohaline circulation) - the movement of warm water around the oceans - thus cutting off the poleward heat transport from the Gulf Stream.
Characteristics of the Loch Lomond Stadial:
-Around 12,500 years ago, the temperatures plunged downwards and, by 11,500 years ago, glacial conditions occurred with temperatures 6-7ºC lower.
-Glacierd re-advanced in many parts of the world including the formation of ice caps in the Scottish Highlands, from which clique and valley glaciers flowed outwards, with smaller areas of cirque glaciers in the Lake District and North Wales.
Cause of the Little Ice Age:
Different causes have been suggested for the Little Ice Age, including:
-Volcanic activity (although climate change on a timescale of hun dress of years and 1-2ºC can’t be explained solely by volcanoes).
-Low levels of solar radiation (caused by a lack of sunspot activity)
Characteristics of the Little Ice Age:
-The Little Ice Age (during the Holocene) was a period of cooling which occurred after the Medieval Warm Period (roughly 950-1250). The Little Ice Age lasted from about 1550-1850, although some define it as starting as early as 1300.
-There was widespread abandonment of upland farms in Scandinavia and Iceland. Farms and villages in the Swiss Alps were destroyed as glaciers advanced.
-Many glaciers in Europe re-advanced down valleys; the Little Ice Age was a period of predominantly positive net mass balance leaving prominent terminal moraines.
-Artic sea ice spread further south with polar bears seen frequently in Iceland. Sea ice extended out from Iceland for miles in every direction - closing its harbours to shipping.
-Rivers in the UK and lowland Europe, and New York harbour, froze over, e.g. a frost fair held on the Thames in 1683.
-Greenland was largely cut off by ice from 1410 until the 1720s.
-Crop practices across Europe had to change to adapt to a shorter growing season - and there were many years of famine.
Explain the short-term causes of climate change (6 marks):
Variations in solar output and volcanic emissions are two short-term cause of climate change. Sunspots are caused by intense magnetic activity in the sun’s interior. a increase in the number of sunspots means that the sun is more active and giving off more energy, so sunspot numbers indicate levels of solar output, and appear to vary over an 11 year cycle. Observations of the sun during the latter part of the Little ice Age (1550-1850) indicate that very little sunspot activity was occurring at the sun’s surface and during this time Europe and North America experienced colder than average temperatures.
The most significant volcanic impact on climate change is the injection into the atmosphere of large quanitities of sulphur dioxide gas, which remains in the atmosphere for as long as 3 years. sulphur aerosols are formed, which increase the reflection of radiation from the sun back into space, cooling the Earth’s lower atmosphere. In 1815, the Indonesian volcano Mount Tomborra produced one of the most powerful volcanic eruptions in recorded history. accounts of very cold weather were documented in the year following the eruption in a number of regions across the planet.
Describe the distribution of high latitude (polar ice sheet - areas of permanent ice) glacier (3 marks):
All of the polar ice sheets are found at high latitudes, within the Antarctic and Artic circles, for example, the polar ice sheet found in Greenland, which spreads approximately 2000km wide.
Describe the distribution of high latitude tundra (periglacial) glaciers (3 marks):
Periglacials are found at the edge of the permanent ice at high latitudes, in the northern hemisphere only. These areas include large tracts of northern Canada (6000km long), Alaska and Russia, mainly outside the Artic circle.
Describe the distribution of high altitude (alpine glacial) glaciers (3 marks):
High altitude glaciers are found on 5 continents, all over the world, other than Antartica and Africa. Alpine glacials include the European Alps, Himalayas, Northern Rockies and Andes.
Compare the present-day distribution. of high latitude ice sheets and the Pleistocene ice sheet extent:
-Ice cover at the Pleistocene maximum was more than 3 times greater than the present day.
-The Antarctic and Greenland ice sheets only covered a slightly greater area than they do today.
-The major extensions at the Pleistocene maximum were two ice sheets in North America (Laurentide and Cordilleran) and the Scandinavian Ice Sheet in Europe - these all grew to thickness of 3000-4000m and transformed the landscape of North America and Europe.
-Other significant extensions include all of souther South America, South Island New Zealand, Siberia and the Himalayas.
cryosphere Definition:
The cryosphere is the frozen part of the Earth’s hydrological system, which consists of ice sheets and glaciers, together with sea ice, lake ice, ground ice (permafrost) and snow cover.
Importance of cryosphere:
-Most important - Mass and energy are constantly exchanged between the cryosphere and other major components of the Earth’s systems: the hydrosphere, lithosphere, atmosphere, and biosphere.
-The cryosphere, mainly glaciers, are very visible and sensitive barometers of climate change. they grow/advance in response to changes in temperature and precipitation.
-The crysophere acts as a store within the global hydrological cycle.
-The components of the cryosphere play a vital role in the Earth’s climate. Snow and ice reflect heat from the sun (albedo effect) which helps to regulate temperatures own Earth.
What is continuous permafrost?
-Forms in the coldest parts of the world (at high latitudes - higher than 65º) - where mean annual air temperatures are between -4 and -40ºC.
-The lower the temperature is, the deeper the continuous permafrost is. it can extend downwards for hundreds of metres.
-The active layer is only between 0.5 - 1.0m.
What is discontinuous permafrost?
-This is kore fragmented and thinner.
-Occurs at lower latitudes (between 60ºN and 65ºN).
-The average temperatures vary from -6ºC at 65ºN to -1ºC at 60ºN.
-As temperature increases, the permafrost becomes less deep and more fragmented. The depth of the permafrost can be as much as 45m.
-The active layer is around 1-1.5m.
What is a polythermal glacier?
A further subdivision is the hybrid polythermal glacier, whereby the underneath is warm (wet) based and the margin cold based. Many large glaciers are cold based in their upper regions and warm based lower down, when they extend into warmer climate zones - this is a common occurrence in Svalbard, Norway.
Factors that influence the distribution and character of permafrost:
-Climate is the main control, as the temperature and the amount of moisture available determine the presence or absence, depth and extent of permafrost.
-Factors that influence the distribution and character of permafrost on a local scale include: proximity to water (e.g. lakes), slope orientation, character of ground surface, vegetation cover, snow cover.
How does proximity to bodies of water influence the distribution and character of permafrost:
Lakes are relatively warm so remain unfrozen throughout the year with a deep active layer. this insulates the ground below, preventing it from freezing permanently.
How does slope angle and orientation influence the distribution and character of permafrost:
Influence the amount of solar radiation, and therefore melting, freeze-thaw and wind. In the Northern Hemisphere, slopes facing North receive much less solar radiation due to the curvature of the Earth (they are more sheltered), meaning there is more likely to be permafrost.
