SM

Part of geo class march 21: Notes on Water and Glaciers

Water and Glaciers Overview

Freshwater Distribution

  • Water Types: 97% of Earth's water is saltwater, only about 3% is freshwater.
  • Sources of Freshwater:
  • Glaciers/Ice caps: Account for about 68.7% of freshwater globally, primarily stored as ice.
  • Groundwater: Second largest source of freshwater, accessed through wells and aquifers.
  • Other sources like lakes and rivers make up a small percentage.

Understanding Glaciers

  • Definition: A glacier is a large mass of ice formed from accumulated snow over years.
  • Characteristics of Glaciers:
  • Large and thick; can range from hundreds to thousands of square kilometers.
  • They take hundreds to thousands of years to form, not seasonal or temporary.
  • Glaciers are dynamic; they flow and deform under their own weight.

Movement of Glaciers

  • Flow Mechanics:
  • Glaciers can move through:
    • Sliding: Ice slips at the base over bedrock due to pressure and water lubrication.
    • Internal Deformation: Ice acts as a viscous fluid, deforming under its weight and flowing.
  • Erosion: Glacial movement erodes the underlying bedrock, creating sediment.

Formation of Glacial Ice

  • Requirements for Formation:
  • Snow Accumulation: Must have multiple layers of snow to form glacial ice.
  • Cold Temperatures: Need cool summers to prevent melting between seasons for net accumulation.
  • Transformation Process:
  1. Freshly deposited snow: Highly porous (up to 90% air), fluffy, and contains ice branches that can sublimate (turn into vapor).
  2. Aging of snow: Over time, snow loses its structure due to sublimation and compaction under added layers.
  3. Formation of granular ice: From fluffy snow to denser, granule-like structures of ice.
  4. Glacial ice: Requires decades to millennia of accumulation, forming dense, cohesive glacial ice with significantly reduced porosity (5-20%).

Environmental Conditions

  • Cold Climate Regions:
  • High Latitudes: Near the poles where snowfall exceeds melt.
  • High Altitude Regions: Mountains where elevation causes cooler temperatures needed for glacial formation.

Temperature Influence on Ice and Snow

  • Explanation of Cold:
  • Solar Radiation Distribution:
    • Lower latitudes receive heat more directly than higher latitudes due to Earth's curve, distributing the same amount of heat over a larger surface area at greater latitudes.
  • Example: Comparatively, a wood stove effectively heats a small house but cannot warm a large castle due to the same output of heat covering a broader area.
  • Pressure and Density:
  • Atmospheric pressure decreases with altitude, leading to thinner air and temperatures that drop, affecting ice and snow persistence.

Summary Points

  • Understanding the distribution and dynamics of freshwater, especially glacial ice, is essential in grasping climate conditions and water conservation strategies.
  • Melting of glaciers—caused by rising temperatures—can significantly influence sea levels, ecosystems, and human water supply.