Topic 6: Snow and Glaciers

Question 1

what is Duffs Ditch referring to?

Answer 1

the floodway built in 1962-1968 when Duff Roblin was premier. second largest earth moving project, designed to protect the city of Winnipeg from a 1 in 700 year flood.

Question 2

name the 4 simultaneous estimation problems

Answer 2

1. quantity of water being held in snowpacks
2. magnitude and rate of water lost to the atmosphere by sublimation
3. the timing, rate and magnitude of snowmelt
4. the fate of meltwater

Question 3

T or F? The extent of sea ice is greater in Northern hemisphere than southern hemisphere?

Answer 3

True. but southern hemisphere has less variance between minimum and maximum ice extents.

Question 4

what does the CCIN do?

Answer 4

CCIN= Canadian cryospheric information network. provides a data and info. management infrastructure for the Canadian cryospheric research community, to enhance public awareness and access to cryospheric info and related data and finally, to facilitate exchange of info between researchers, northern communities, decision makers and public.

Question 5

Macroscale snow cover distribution

Answer 5

areas up to 10^6 km2
characteristic distances of 10-1000km
larger scale meteorological effects are important

Question 6

mesoscale snow cover distribution

Answer 6

• characteristic distances of 100m to 10km
• redistribution of snow along relief features due to wind
• deposition and accumulation of snow may be related to terrain variables and vegetation cover

Question 7

microscale snow cover distribution

Answer 7

distances up 10-100m

- differences in accumulation result from variations in air flow patterns and transport

Question 8

T or F: snow cover is also influenced by the interaction of winds with vegetation and the terrain?

Answer 8

true

Question 9

snow accumulation in coniferous vs deciduous trees

Answer 9

coniferous: lots of snow in trees, little on ground
deciduous: little snow in trees and deep snow on ground

Question 10

snow accumulation in clearings vs forested areas

Answer 10

20%-45% greater accumulation in clearings

Question 11

will snow accumulate downwind or upwind of forest?

Answer 11

more snow may accumulate downwind of trees

Question 12

T or F: snow in trees is more prone to sublimation

Answer 12

true

Question 13

describe snowpack characteristics

Answer 13

• porous medium
• generally composed of layers of different types of snow (usually homogenous within the layer)
• ice is in form of crystals and grains that are usually bonded together

Question 14

fresh snow vs drifted settled snow visual

Answer 14

fresh snow looks like a flake meanwhile drifted snow is more compact

Question 15

what is SWE and what does it stand for?

Answer 15

SWE: snow water equivalent
hydrologists are interested in knowing how much snow is on the ground in water equivalent
depth*density of snow/density of water. 
fresh snow density ~100kg/m3
settled snow density ~200-300kg/m3

Question 16

Dry snow definition and water content (percent)

Answer 16

snow temp below 0C, little tendency to adhere together, consists of aggregated snow grains. hard to make a snowball. 0% water content

Question 17

moist snow definition and water content

Answer 17

snow temp at 0C, water not visible at 10x magnification. when lightly crushed snow tends to stick together, easy to make snowballs. <3% water content

Question 18

wet snow definition and water content

Answer 18

snow temp 0C and can recognize water at 10x magnification. cannot press out water. 3-8% water content.

Question 19

very wet snow definition and water content

Answer 19

snow temp 0C, water can be pressed out by moderately squeezing hand but some air still confined within pores. 8-15% water content.

Question 20

slush snow definition and water content

Answer 20

snow temp 0C, snow is flooded with water and contains a relatively small amount of air. >15% water content.

Question 21

water flow through snow: velocity and factors

Answer 21

velocities: 2-60cm/min
factors:
internal snow pack structure
condition of snow pack prior to introduction of water
amount of water available at snow surface

Question 22

water flow through homogenous snow

Answer 22

• at melting temperature, thin film of water surrounds each snow grain
• much of the water can flow through this film
• once pores are filled, laminar flow can occur
• very efficient mechanism for draining the snow pack

Question 23

water flow through heterogeneous snow

Answer 23

–preferential flow paths
dye studies reveal vertical channels or macropores in most natural
snowpacks
–ice layers:
-develop from surface melt or refreezing
-relatively impermeable
-forces ponding of water and lateral flow

Question 24

list and describe the 4 liquid water regimes

Answer 24

1. capillary: <1% free water. water doesn’t drain due to capillary tension
2. unsaturated: 1-14% free water. water drains by gravity but air spaces continuous, pendular regime
3. saturated: >14% free water. water drains by gravity but air spaces are discontinuous. Funicular regime.
4. Melt/Freeze: water melts and refreezes, possible several times before it drains from snowpack

Question 25

Surface melt: thawed soil vs frozen soil

Answer 25

thawed soil: snowmelt at a rate less than infiltration will allow for entry into soil, behaves like rainfall.
frozen soil: creates ponding at soil surface

Question 26

Hydrographs in snow dominated catchments

Answer 26

huge surge in late spring early summer.

Question 27

primary permeability

Answer 27

• intact ice and snow
• high for snow and firn: linked pore spaces
• very low for ice

Question 28

secondary permeability

Answer 28

• tunnels and passage ways

- most water draining through glaciers

Question 29

Supraglaial

Answer 29

streams, lakes, snow aquifer

Question 30

englacial

Answer 30

crevasses, moulines, fractures

Question 31

subglacial

Answer 31

channels, cavities, sheets, canals, groundwater

Question 32

T or F: water in a glacier follows the same rules as it does elsewhere in hydrology?

Answer 32

True

Question 33

subglacial drainage equipotential lines

Answer 33

• direction of flow determined by hydraulic potential

equipotential lines:
-pressure of overlying ice is equal to water pressure it generates
-geometry determined by variation in ice thickness (major) and slope of underlying topography (minor)
- water will flow to the snout at right angles to equipotential contours.
operates at high pressure

Question 34

subglacial drainage through the seasons

Answer 34

stops in winter when there is no water supply at surface. can be subglacial water ponded in distributed lakes and cavities at this time of year. Come summer, bed is flooded with water and channels from melting through the ice. these follow hydraulic gradients to the nearest exit: side margin or glacier terminus.

Question 35

where does water come from in these mountainous areas?

Answer 35

ice melt
snow melt
rainfall
runoff from ice-free slopes
release of stored water

Question 36

seasonal evolution of glacier water reserves (snow accumulate, melt, intensifying, etc)

Answer 36

1. snow accumulates September to May
2. snow melts May and June with some runoff but poorly drained from undeveloped drainage system
3. intensifying snow and ice melt July and August
4. September transition back to winter, basal and groundwater drainage through fall

Question 37

Glacier impact on catchment runoff

Answer 37

can be important in summer for dry places as it acts as a reservoir
can store water for decades to centuries which helps buffer streamflow. cold wet years-less runoff but warm dry years- more runoff.

Question 38

impact of climate change on glacier size and melt

Answer 38

as years get hotter, glaciers are shrinking and melting sooner than June, creating issues for hydro power as its peak demand is in late june.