Cryosphere Lecture 4

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How climate affects ice
Direct impacts of climate on ice On mass balance – ablation & accumulation 1. Glaciers 2. Greenland 3. Antarctica 4. Sea ice Indirect impacts of climate on ice Role of surface meltwater in controlling ice dynamics Role of ocean circulation changes
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Glaciers are Sensitive to small changes in the climate aka
Increase temperatures => increase melting Causes the mass balance to become negative (assuming accumulation does not increase as well) Changes the ELA Leads to a change in configuration
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Glaciers General retreat trend though
Not constant Retreat since Little Ice Age (~ 16th C to 19th C) ‘Global cooling’ period (1950 - 1980)
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Europe - Norway
Maritime glaciers advanced 1980s-2000 Retreat since 2000 Linked to strong positive North Atlantic Oscillation causing increased westerlies increased accumulation (Chinn et al., 2005)
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Example of a glacier in Norway
Briksdalsbreen, an outlet glacier of Jostedalsbreen, Norway,
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New Zealand has a Similar pattern to Norway
Mid 1980s glacier advance Retreat since 2000 Linked to ENSO and IPO (Interdecadal Pacific Oscillation) Increased westerlies Increased accumulation
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Glaciers very sensitive to small amounts of temperature change Showing retreat trend worldwide
A function of warming temperatures but also includes response to local variability, e.g. ENSO (New Zealand) or NAO (Norway).
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Greenland has a seen a direct impact of climate in terms of Mass Balance Change
Increase in ablation in coastal areas More accumulation high up Does not counteract decrease in coastal areas Hence will have a –ve overall mass balance => system not in balance => thinning
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Antarctica - Impact of Climate change
Most of Antarctica is insensitive to small atmospheric temperature changes and On the Antarctic Peninsula, mean annual temperatures are higher, can be above 0°C.
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Ice retreat & thinning at the northern end
of the Antarctic Peninsula e.g. South Shetland islands
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Sea ice extent Arctic sea ice is
decreasing Part global warming, part natural variability (Serreze et al., 2007)
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Antarctic sea ice extent is not
decreasing In fact it is showing a slight increase in area Polar amplification mechanism isn’t as strong due to land/sea configuration
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Role of surface meltwater Meltwater has a large impact on the cryosphere
Can flow on top of the ice (supraglacial) inside the ice, in tunnels (englacial) or underneath the ice (subglacial)
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Supraglacial meltwater can reach the base of the ice
=> Subglacial water can increase the velocity of the glacier
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2. Supraglacial meltwater can cause weakness in ice shelves
=> causing ice shelf collapse
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1. Greenland, ‘Zwally effect’ Theory:
Surface meltwater ponds drain through moulins to the base of the ice  ice velocity increases
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Antarctic Peninsula
Ice shelf breakup caused by surface meltwater ponds weakening ice shelf (Scambos et al., 2000)
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other issues on the Antarctic Peninsula include:
Ice shelf breakup Ice shelves ‘buttress’ glaciers/ice streams flowing into them Remove this buttressing => glaciers speed up & thin
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Widespread ice shelf retreat Response to
local rapid temperature increase
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Role in changing ocean circulation
Wind direction alters ocean circulation Temperature impacts on marine based ice
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Card 2

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Glaciers are Sensitive to small changes in the climate aka

Back

Increase temperatures => increase melting Causes the mass balance to become negative (assuming accumulation does not increase as well) Changes the ELA Leads to a change in configuration

Card 3

Front

Glaciers General retreat trend though

Back

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Card 4

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Europe - Norway

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Preview of the front of card 4

Card 5

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Example of a glacier in Norway

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