14. The Cryosphere Flashcards
What is the cryosphere?
frozen water part of the earth system
Where is the cryosphere?
poles and high altitudes
Give up to 7 types of the cryosphere
- ice sheets
- ice caps
- ice shelves
- glaciers
- permafrost
- icebergs
- sea ice
permafrost=
ground that stays frozen year-round
ice sheet=
mass of glacial land ice extending more than 50,000km^2
how do ice sheets form?
formed by accumulation of snow; layers on the bottom get compacted by weight of new layers, forming ice
Where are ice sheets found?
antarctica and greenland
___ ____ are miniature ice sheets
ice caps
glaciers=
a mass of ice in constant slow motion, flowing downhill under their own weight
T/F
like ice sheets, glaciers are also formed by accumulation of snow that compacts into ice
true
what are glaciers nicknamed?
rivers of ice
ice shelf=
when ice sheets extend over the sea and float on the water
iceberg=
massive piece of ice (larger than 5m) greatly varying shape, which may be found floating in the ocean or aground
How do icebergs form?
when chunks of ice calve, or break off from glaciers, ice shelves, or a larger iceberg
Most icebergs encountered in Canadian waters are calved from the glaciers of:
western greenland
Icebergs are important for transporting ______ and _______
freshwater and nutrients
Transport of large icebergs is controlled mainly by what?
water currents
winds become more important to icebergs having high sail (lots of it is out of the water)
How long does it take for an iceberg to float from the west coast of greenland to the grand banks of newfoundland?
2-3 years avg
sea ice=
ice that forms, grows, and melts in the ocean
- no origination on land
For typical ocean salinity, seawater freezes at __C
-1.8C
__% of the world’s oceans are covered by sea ice during part of the year
15
grease ice=
a smooth, thin form of ice formed by frazil crystals
- this forms during calm conditions
grease ice develops into a continuous, thin sheet of ice called
nilas
During agitated conditions, what do frazil crystals form?
pancake ice
= frazil crystals accumulate into slushy circular disks
- raised edges or ridges on the perimeter, caused by the pancakes bumping into each other
Explain the pathway of sea ice formation if conditions are rough
rough ocean= pancake cycle
frazil ice –> pancake ice –> rafting or ridging –> cementing and consolidation –> sheet ice (rough-bottomed)
explain the process of sea ice formation is conditions are calm
calm ocean= congelation growth
frazil ice –> nilas –> rafting –> congelation ice –> sheet ice (smooth bottomed)
brine rejection=
when frazil ice crystals form, salt accumulates into droplets called brine, which are typically expelled back into the ocean
What implication does brine rejection have for salinities at different water depths?
increases salinity of near-sfc water
–> water underneath the newly formed ice has higher density, so sinks and mixes with water masses below
Does brine typically remain in a liquid or solid state?
liquid
- much colder temps required to freeze brine
In freshly formed sea ice, there is some liquid brine content. Over time, this drains out, leaving __ pockets and the salinity of the sea ice __(inc/dec)
air
decreases
First year ice=
When temp increases in spring and summer, the sea ice begins to melt. If the ice doesn’t grow thick enough during the winter, it’ll completely melt during the summer = 1st yr ice
Multi year ice=
if the ice grows thick enough during the winter, it thins during the summer but doesn’t completely melt
- It’ll remain until the following winter, when it’ll grow and thicken again = multiyear ice
First year ice is usually __-__m thick. Explain its topography, freeboard (portion about water level) and salt content
0.3-2m
relatively level topography
low freeboard
higher salt content
Multiyear ice is usually __-__m thick (up to __m). Explain its topography, freeboard (portion about water level) and salt content
2-4m up to 7m
more variable topography
high freeboard
lower salt content
Once a sheet of ice has formed, how can it increase its thickness?
freeze the water on its lower surface
How does salinity change as ice gets older? How does this change freeboard?
older ice gets= less salt concentration in it
stands higher out in the ocean b/c it’s less dense= higher freeboard
T/F
Ice with very high freeboard is more common in the Antarctic than the Arctic
false
most common in the arctic, rarer in antarctic
Sea ice has 1 way to grow and 4 ways to melt. List them
1 grow: from bottom
melt:
- top
- bottom
- internal
- lateral
Pancake ice and grease ice are classified as “___ ice” and are less than __cm thick
new
10cm
Nilas is classified as “___ ice” and is __-__cm thick
young
10-30
How thick is 1st year ice? Multiyear ice?
30cm-2m
multi= 2+m
T/F
Sea ice is typically a continuous, uniformly smooth sheet of ice
FALSE
it’s a very complex surface that can vary dramatically across even short distances
Pressure ridges in sea ice can be formed in 2 ways:
- from the pressure exerted on the ice by the force of wind/ tide
- from thermal expansion
When does rafting occur?
when 2 floes are pressed together in such a way that one over-ridges the other in a continuous manner
_____ and _____ are regions of open water within an expanse of sea ice
leads and polynyas
Give some differences between leads and polynyas
Leads=
- narrow, linear areas of open water
- form because of the motion of the ice
- during winter, open water remains in leads for only a short time, then refreezes
Polynyas=
- more uniform in shape and larger in size
- form from either upwelling warm water or persistent winds
- usually remain unfrozen for long periods of time
What kind of heat would likely be lost from a coastal polynya? What about an open ocean polynya?
coastal= latent
open ocean= sensible
Why is there a positive feedback loop between climate warming and sea ice loss?
The albedo effect
temp rises= sea ice loss= sfc albedo decreases= ocean absorbs more heat= temp rises
How is a coastal polynya formed?
winds from the shore push newly formed ice away from the coast= open water along the coast.
Brine formation under the newly formed ice results in cold, dense water under the coastal polynya
How is an open ocean polynya formed?
Upwelling of warmer water.
- colder, dense water sinks
- sensible heat lost through open water
