Topic 2 - EQ 1 Flashcards
How old is the earth estimated to be?
4.6 Billion years old.
What are the two dominant states our earth fluctuates between?
Greenhouse earth and icehouse earth.
When does a greenhouse earth occur?
When there are no continental glaciers on the planet as a result of warming processes, such as higher levels of greenhouse gasses in the atmosphere. This could be caused by ,for example, increased volcanic activity.
What is an icehouse age?
This is a global ice age, when large ice sheets are present on the earth. During this time, the earth fluctuates between cooler glacial periods (where ice advances) and warmer interglacial periods (where ice retreats).
How have temps on earth changed in the last 2 million years?
In the last 2 million years (start of Quaternary and Pleistocene period) temperatures on earth have fluctuated considerably. This has led to cold periods (glacials) and warm periods (interglacials).
How many glacial periods have there been in the last 1 million years?
In the last 1 million years, there may have been as many as ten glacial periods – separated by interglacials.
What age are we currently in?
There are five known ice ages in the Earth’s history, the most recent being the Quaternary Ice Age - 2.6million years ago to present day. It is divided into two epochs:
- The Pleistocene, which lasted until approx. 11,500 - 12000 years ago
- The Holocene, which began 10,000 years ago and continues today
What are the three main characteristics of the Pleistocene?
- It wasn’t just a single ice age. Over the 2 million or so years during which it lasted, temperatures fluctuated enough to allow a number of ice advances and retreats.
- The extent to the ice advance during each glacial was different.
- There are fluctuations within each major glacial. These relatively short-lived pulses of ice advance are known as stadials, and warmer periods of retreat known as interstadials.
What are stadials?
Short lived pulses of ice advances.
What are interstadials?
Warmer periods of retreat between stadial periods.
What was the most recent continental glacial?
The UK Devensian. This was 18,000 years ago. The last glacial advance was the Loch Lomond Stadial, which was between 12,000 and 10,000 years ago. This marked the end of the Pleistocene epoch.
Are we currently in a glacial or interglacial period?
Currently, we are in an interglacial period. This is called Holocene. The last glacial period ended roughly 12,000 years ago and was called the Pleistocene.
What is the long term causes of climate change?
The start of the quaternary period has been linked to the changing position of the continents, a result of plate tectonics. Three million year ago the North and South American tectonic plates collided, creating the Panama Isthmus (narrow land bridge joining the two continents). As a result, ocean currents were re-routed, so the warm Caribbean waters once flowing through the Panama Isthmus we forced northwest to Europe.
Scientists believe the formation of this Gulf Stream transported extra moisture into the arctic atmosphere, and this feel as snow, which triggered the build-up of the Greenland ice sheet. This may of caused the last Ice Age.
What are Milankovitch’s cycles?
The geophysicist proposed the glacial-interglacial cycles were caused by variations in the amount of solar radiation received by the earth. This is a result of three cyclical changes in the orbit and axis of the Earth. Evidence from coral reefs in Barbados reveals that there is a strong correlation between the timing of the interglacial periods in the past 160,000 years and eccentricity cycles. This indicated that Milankovitch cycles are a primary driver of climate change.
What is eccentricity?
The shape of the earth’s orbit varies from circular to elliptical over 100,000-year cycles. The earth receives less solar radiation in the elliptical orbit when the Earth is farthest from the sun. This position is known as aphelion.
What is obliquity?
The tilt of the earth’s axis varies between 21.5° and 24.5° over 41,000 year cycles. This changed the severity of the seasons.
What is precession?
The Earth wobbles as it spins on its axis, which means that the season during which the earth is nearest to the sun (a position known as perihelion) varies. At present, the northern hemisphere winter occurs in perihelion i.e Milder conditions than in previous winters in aphelion. This varies over approximately 21,000 year cycles resulting in a change in the intensity of the seasons.
What are the two short term causes of climate change?
Solar output variation
Volcanic emissions
How do volcanic emissions cause short term climate change?
April 1815 saw theIndonesian volcano Mount Tambora produced one of the most powerful volcanic eruptions in recorded history. Accounts are very cold weather were documented in the years following the eruption in a number of regions across the planet. Although scientists initially thought this was due to ash by partially blocked the transmission of solar radiation. However, this was proven to clear within months. The most significant impact was sulphur dioxide which was injected in large quantities. It remains as long as 3 years. Sulfur aerosols are formed, which increases the reflection of solar radiation back into space from the sun, cooling the earth’s atmosphere as a result.
How do variations in solar output cause short term climate change?
For hundreds of years, scientists have regularly counted the number of dark patches on the face of the Sun. These are caused by intense magnetic activity in the Sun’s interior. An increase in these sunspots means the sun is more active, giving off more energy, so sunspot numbers indicate levels of solar output. They also appear to vary over an 11 year cycle.
How much sulfur dioxide did Mount Tambora eject?
200 million tonnes. The following 2-3 years saw temps 0.4-0.7°C lower than before recorded.
What is Climate Feedback?
Feedback effects are those that can either amplify a small change and make it larger (positive feedback) or diminish a change and make it smaller (negative feedback). A number of interacting earth systems are involved.
What are some examples of positive climate feedback?
Snow and ice cover. Small increases in snow/ice raise surface albedo (reflectivity) so more solar energy is reflected back into space, leading to further cooling and further snowfall and ice cover.
The melting of snow/ice cover by carbon dioxide emissions decreases albedo; methane is emitted as permafrost melts, and warming seas lead to calving of ice sheets, which all lead to loss of snow/ice cover and surface albedo. This decreases reflection and accelerates further warming.
What are some examples of negative climate feedback?
Increasing global warming leads to more evaporation end, over time, pollution from industrialisation adds to global cloud cover. Increasingly cloudy skies could reflect more solar energy back to space and diminish the effects of warming – so called ‘global warming’ may be less intense because of this global dimming.
Ice sheet dynamics can disrupt the Thermo healing circulation. Warming water in the Arctic disrupts ocean currents; less warm water from the Gulf stream is drawn north, which could lead to global cooling in Northern Europe.
What were the characteristics of the Loch Lomand Stadial?
Despite ice sheets retreating 18,000 years ago, and rapid deglaciation 15,000 years ago, about 12500 years ago temps plunged. By 11,500 years ago, they had fallen 6-7°C. This the allowed glaciers to re-advance, including formation of ice caps in the Scottish highlands, where cirque and valley glaciers flowed outwards.
After the Loch Lomand Stadial, temps rised by 7°C in 50 years, as well as massive sea level rises.
What was the cause of the Loch Lomand Stadial?
One possibility is that it was triggered when drainage of the huge proglacial Lake Agassiz disrupted the Thermohaline circulation, thus cutting off the poleward heat transport from the Gulf stream, allowing the ice to advance.
What were the characteristics of the Little Ice age?
Little ice age lasted from about 1550-1850, but some define it as starting from 1300. Temps fells by 1-2.0°C for hundreds of years.
Sea ice extended outwards from Iceland for miles in every direction.
Many glaciers in Europe re-advanced down valleys.
Rivers in the UK, Europe and New York froze over due to the fall in temperature.
Curling developed as a national sport in Scotland as there was so many frozen rivers and lakes.
What cause the Little Ice Age?
It hasn’t been completely agreed on, however it is thought to be a mix between reduce solar radiation and volcanic activity. However, climate change which occurs over hundreds of years and 1– 2°C can’t be from the volcanic activity alone and low levels of solar radiation.
Some researchers believe the little ice age could have developed into a new Stadial, but the carbon dioxide released from the Industrial Revolution prevented this Stadial.
What is the cryosphere?
This consists of ice sheets and glaciers, together with sea ice, lake ice, ground ice (permafrost) and snow cover. They’re parts of the Earth’s crust and atmosphere subject to temps below 0°C for at least part of each year.
What are the 4 key roles of the cryosphere?
-It acts as a large store in the global hydrological cycle. This includes ice sheets in Greenland and Antarctica, + frozen rivers, oceans etc
- Causes albedo affect - snow and ice reflects heat back out the atmosphere to help regulate earth’s temps.
- Mass and energy constantly get transferred/exchanged the cryosphere and other major earth systems: hydrosphere, lithosphere, atmosphere, biosphere.
- glaciers are Important for climate scientists analysing climate change. They advance and retreat in response to changes in temp and precipitation.
What is an ice sheet? What is its average size?
What is an example of an Ice Sheet?
-They are UNCONSTRAINED. A complete submergence of regional topography; forms a gently sloping dome of ice several kilometres thick in the centre. Only the highest mountain peaks (known as nunataks) will be above the ice.
-10-100,000 squared kilometres
- Greenland Antarctica
