L6: Feedback Relationships and Response Times
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is albedo an example of a positive or negative feedback cycle?
positive
what is albedo?
the amount of incoming solar radiation (insolation) reflected back into space as a result of the surface reflectivity of materials on the earth surface
what is insolation?
incoming solar radiation
what is an example of a high albedo surface?
snow
what is the basis for the phenomenon of Arctic amplification?
ice melts leading to more ocean surface becomming exposed which has low albedo. resulting in more ice melting
do clouds all have the same albedo?
no
what has higher albedo? fresh snow or ice?
fresh snow- extremely high reflectivity
what are examples of low albedo surfaces?
dense forest vegetation and in particular the ocean surface
what percentage albedo does fresh snow have?
80%-90%
what percentage albedo does debris covered ice have?
10%-15%
why do you typically see ice melt surrounding boulder on the surface of a snow pack surface?
because its absorbing incoming solar radiation from the sun and heating up
what area experiences the fastest rate of warming?
the Arctic
why does the Arctic experience faster rates of warming compared to mid-latitude areas and the Antarctic?
because of the phenomenon Arctic amplification caused by the difference in albedo between the ocean and sea ice
what is this a description of? continent situated over the south geographic pole and surrounded by a massive ocean.
the Antarctic
what is this a description of? a big ocean surrounded by a continent.
the Arctic
what forms when the surface of the Arctic ocean freezes?
sea ice
what temperature does normal marine seawater freeze?
-1.91 degrees
how does a positive feedback loop start in the Arctic?
sea ice has a much higher albedo than the ocean. so the ocean water absorbs heat whilst the ice reflects incoming solar radiation. therefore, a temperature increase starts to melt the sea ice, increasing the areal extent of the highly absorbent ocean; triggering a positive feedback loop as it warms up the system
why doesn’t the same amplification take place in the Antarctic?
because it is not an ocean
what is a snowball Earth?
when snow cover is so extensive, ice caps cover the entire surface of the Earth
is snowball Earth an example of a positive or negative feedback?
positive
what is evidence for snowball Earth?
Namibia (southern part of Africa)- sediment characteristic of being a glacial sediment. fine grained sediment and large boulders set within very coarse fine sediment. poorly sorted
true or false? we have been glaciated for most of Earth’s history.
false- for most of Earth’s history, we have had no glacier or major ice sheets
what is a bipolar glaciation?
presence of major ice sheets at both poles