ATS2545 Lecture Notes - Lecture 15: Arctic Ocean, Firn, Thermohaline Circulation
25 May 2018
School
Department
Course
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Lecture 12 – Hydrology of Snow and Ice
Essay
Average mark: 67.2
Pass: 17.6%
Credit: 29.4%
Distinction: 29.4%
HD: 17.6%
Importance of snow and snowmelt runoff
• Not directly important in Australia because no permanent snow
• Majority in northern hemisphere
• Seasonal snow in southern hemisphere
o New Zealand
• Fate of arctic sea ice
o Decreasing dramatically over the years
Conversion of snow to ice
• Most fresh water on planet is in frozen form in Antarctica and Greenland
• Fresh snow has low density
o Much entrapped air: low as 0.05 g cm3
• Melting and compaction cause the snow to become more densely packed
o Final product, dense ice: 0.8 – 0.92 g cm3
• In Greenland: formation of ice takes ~100 years
• Firn
o Partially compacted know
• Ice has a pressure melting point and temperature melting point
o Since it is less dense than water
• Main process through which ice is formed is by re-freezing of water that has
reached pressure melting point
• Ice
o Isotopically very light
▪ Moisture travels to high elevation
▪ Large O18 delta scores
• Fraction of precipitation that is received as snow increases pole wards and
with elevation
o Commonly 5-40% but reaches 65% along N coast of Alaska
• Snow does not evaporation significantly
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