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Glaciology > L4 & 5 - Glacier Hydrology > Flashcards

L4 & 5 - Glacier Hydrology Flashcards

1
Q

Give 3 water sources in glacial environments

A
  1. Snow Melt
  2. Ice Melt
  3. Rain
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2
Q

What are the 4 Hydrological Environments (with definitions)?

A
  1. Supraglacial (On top of the Ice)
  2. Englacial (In the Ice)
  3. Subglacial (Beneath the Ice)
  4. Proglacial (In front of the Ice)
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3
Q

What is a moulin?

A

A nearly vertical channel in ice that is formed by flowing water, usually found after a relatively flat section of a glacier in a region of traverse crevasses

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4
Q

Give 3 points about water movement in the supraglacial environment

A
  1. Surface meltwater flows down glaciers in supraglacial streams
  2. Water collects in supraglacial lakes bounded by ice
  3. Drains down moulins
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5
Q

Where does water go in the Englacial environment?

A

Conduits, cracks and tunnels within the ice – Water takes the area of least resistance

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6
Q

What type of river systems are common in the Proglacial environment?

A

Braided River Systems with daily fluctuations and high sediment load giving milky water

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7
Q

Why is the subglacial environment important?

A
  1. For the microbial environment

2. For glacier movement

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8
Q

What 3 things do we want to know about the subglacial environment?

A
  1. How much water there is
  2. How fast the water is moving
  3. Where the water is
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9
Q

What 4 things do we observe in the subglacial environment?

A
  1. Discharge
  2. Water Transit Times and Flow Paths
  3. Suspended Sediment Concentrations
  4. Solute Concentrations
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10
Q

What are the 8 subglacial methods of enquiry?

A
  1. Waiting for Retreat
  2. Hydrochemistry
  3. Radar
  4. GPS
  5. Satellites
  6. Dye & Gas Tracing
  7. Bulk Meltwater Monitoring
  8. Boreholes
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11
Q

What does a high EC indicate?

A

High solute obtained from long rock:water contact times, indicating a slow and inefficient system

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12
Q

EC and Q are shown on what type of graphs and what is their relationship?

A

EC - chemograph
Q - hydrograph

They are the inverse of one another

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13
Q

What are the +ves of insitu subglacial enquiry methods?

A

Real data with detailed measurements

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14
Q

What are the -ves of insitu subglacial enquiry methods?

A

Expensive, small snapshot and a chance that data will be missing in places

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15
Q

What are the +ves of exsitu subglacial enquiry methods?

A

Cover large areas, easy to repeat and relatively cheap

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16
Q

What are the -ves of exsitu subglacial enquiry methods?

A

Need ground truthing and it is hard to measure processes

17
Q

What do observations of drainage system morphology tell us?

A
  1. Large Volumes of Water
  2. Channels can carve into the rock
  3. Channels aren’t always full of water
18
Q

A channelised system is……..

A

Fast and efficient with low water pressure

19
Q

A distributed system is……

A

Slow and inefficient with high water pressure

20
Q

Give an example of a distributed system

A

A Linked Cavity System

21
Q

What are the 3 types of channelised system and their characteristics

A
  1. Nye Channels - carved into rock
  2. Röthlisberger Channels - melted upwards into the ice
  3. Clarke Channels - a bit of both and unconsolidated sediments
22
Q

What is required for the drainage system to remain open and not freeze over?

A

High Water Flow

23
Q

What 2 types of information can you get from dye tracing?

A
  1. Transit time, channel full or pressurised flow

2. Dispersivity

24
Q

What is transit time?

A

The time from injection to peak

25
Q

What is a typical discharge for a distributed system?

A

~0.01 m/s

26
Q

What is a typical discharge for a channelised system?

A

~1 m/s

27
Q

What can happen to drainage systems over the ablation season?

A

They can evolve from distributed systems into channelised systems

28
Q

What type of glaciers have demonstrated that drainage systems can evolve seasonally?

A

Alpine

29
Q

What is an outburst event?

A

A sudden release of subglacial water with a high sediment load

30
Q

What can happen as a result of an outburst event?

A

Meltwater can access new areas of the bed and cause drainage system reorganisation

Glaciology (8 decks)

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