Water Lecture 1

GEOL 142: Water

Lecture 1: Water Cycle-Properties of Water

The Global Water Cycle (Ruddiman, 2014, Box 2-3)

• Water Cycle

  • Oceans: Largest water reservoir on Earth.

  • Water leaves the ocean by evaporation, driven by the Sun's energy.

  • Evaporation requires a huge amount of energy.

  • Ocean water is 3.5% salt – when it evaporates, salt is left behind.

  • Clouds are pure water, carried by winds across land.

  • Precipitation occurs due to temperature changes (rain or snow).

  • Water falls on land as meteoric water, infiltrates into the ground, or forms rivers and streams.

  • Runoff moves water from high to low elevations, feeding lakes or returning to oceans.

  • The water cycle directly contributes to climate change.

Berner and Berner, 1996

• Reservoirs of Water (Berner & Berner, 1996)

  • Oceans contain 97% of Earth’s surface water.

  • Icecaps & glaciers hold 99% of the remaining freshwater.

  • As glaciers melt, water flows into oceans.

  • Groundwater makes up 1% of total water.

  • Smaller reservoirs are more susceptible to change.

  • Sea level rising: 0.14 inches per year (~10-20 cm in the past 20 years).

  • In the past, oceans were 60-100 meters lower due to more ice on land

• Phases of Water (Ruddiman, 2014, Box 2-3)

  • Water exists as solid (ice), liquid (water), and vapor (water vapor).

  • Earth is the only planet with all three states due to its temperature range.

  • Density changes with temperature:

  • Water density decreases as temperature increases.

  • Ice is less dense than water (unusual property).

  • Water is most dense at ~4°C, which helps aquatic life survive in winter.

• Water Vapor and Temperature (Ruddiman, 2014, Fig. 2-13)

  • Positive relationship between water vapor and temperature.

  • At 0°C, air holds 5 g/m³ of water vapor.

  • At 30°C, air holds 30 g/m³ (6x more moisture).

  • Warmer air holds more moisture, leading to heavier precipitation.

Structure of Water Molecules (Feinman, Penn State University)

• Water is a polar molecule (partial positive and negative charges).

• Hydrogen bonding allows water molecules to interact strongly.

• Large energy input required to break hydrogen bonds.

Heat Capacity and Energy (Avogadro’s Number & Atomic Weights)

• Avogadro’s number: 6.022×10²³ atoms = 1 mole.

• Heat capacity: Energy required to raise the temperature of 1 mole of a substance by 1 K.

• Water resists temperature change 30x more than lead.

• Atomic weights:

  • Water (H₂O): 18 grams/mole.

  • Sodium chloride (NaCl): ~59 grams/mole.

• Water has a high heat capacity, affecting climate and temperature regulation.

Energy and Water Phase Changes (Ruddiman, 2014, Fig. 2-12)

• Energy absorbed/released during phase changes (solid-liquid-gas).

• Latent heat of vaporization: Requires a large energy input.

• Sun provides energy for melting, evaporation, and condensation.

Solar Heating: Land vs. Ocean (Ruddiman, 2014, Fig. 2-10)

• Temperature variation is greater over land than over oceans.

• Oceans absorb and store heat more effectively.

• Tropical areas have less seasonal temperature variation.

Climate System and Forcing Factors (Ruddiman, 2014, Fig. 1-5)

• Forcing (Causes of Climate Change):

  • Tectonic processes (>10⁶ years) – CO₂ release, ocean circulation, landmass shifts.

  • Orbital changes (10⁴-10⁵ years) – Milankovitch cycles.

  • Solar radiation strength (10¹ years) – Variations in sunlight.

  • Anthropogenic forcing – Greenhouse gases and land surface alterations.

• Climate System Components:

  • Atmosphere, ocean, ice, land surface, vegetation – all interact dynamically.

• Feedback Loops & Key Processes:

  • Greenhouse effect: CO₂, CH₄, and H₂O trap heat.

  • Ocean circulation: Upwelling, deep water formation, carbon cycling.

  • Weathering & CO₂ cycling: Rocks remove CO₂; volcanic activity adds it.

  • Hydrological cycle: Evaporation, precipitation, river runoff affect climate.

• The vertical line is at 0℃ 

  • Everything to the right of 0℃ is liquid water

• What happens to the density of water when we increase the temperature?

  • As the temperature increases, the density decreases

• It doesn’t happen with most substances – miracle of water 

  • Ice floats on water (Ice is less dense than water)

  • Is it weird that ice is less dense than water? – unusual for the solid to be less dense than the liquid

• The bottom of a body of water is the maximum density

  • About 4℃– where animals stay over the winter

Water vapor content of air. Ruddiman, 2014, Fig. 2-13.

• Water Vapor and Temperature (Ruddiman, 2014, Fig. 2-13)

  • Positive relationship between water vapor and temperature.

  • At 0°C, air holds 5 g/m³ of water vapor.

  • At 30°C, air holds 30 g/m³ (6x more moisture).

  • Warmer air holds more moisture, leading to heavier precipitation.

• Global Temperature and Water Cycle (IPCC Report AR6, Fig. 2.1, 2023)

• Global temperature increased by 1.3°C (2°F) from 2011-2020.

• More heat → More water in the atmosphere → Increased fugacity (escape of water molecules as vapor).

• Structure of Water Molecules (Feinman, Penn State University)

  • Water is a polar molecule (partial positive and negative charges).

  • Hydrogen bonding allows water molecules to interact strongly.

  • Large energy input required to break hydrogen bonds.

• Heat Capacity and Energy (Avogadro’s Number & Atomic Weights)

  • Avogadro’s number: 6.022×10²³ atoms = 1 mole.

  • Heat capacity: Energy required to raise the temperature of 1 mole of a substance by 1 K.

  • Water resists temperature change 30x more than lead.

• Atomic weights:

  • Water (H₂O): 18 grams/mole.

  • Sodium chloride (NaCl): ~59 grams/mole.

  • Water has a high heat capacity, affecting climate and temperature regulation.

• Hydrogen has one electron and one proton.

  • Oxygen has eight electrons.

  • They bond together, forming a polar molecule with a concentration of positive charge (2 protons) at one end and negative charge on the lower half due to extra electrons.

  • The positive end of one water molecule attracts the negative end of another, creating hydrogen bonds that give water its structure.

  • All water molecules interact due to polarity.

  • A huge amount of energy is required to separate water molecules.

• Energy and Water Phase Changes (Ruddiman, 2014, Fig. 2-12)

  • Energy absorbed/released during phase changes (solid-liquid-gas).

  • Latent heat of vaporization: Requires a large energy input.

  • Sun provides energy for melting, evaporation, and condensation.

• Solar Heating: Land vs. Ocean (Ruddiman, 2014, Fig. 2-10)

  • Temperature variation is greater over land than over oceans.

  • Oceans absorb and store heat more effectively.

  • Tropical areas have less seasonal temperature variation.

Ruddiman, 2014, Figure 2-10.

• Climate System and Forcing Factors (Ruddiman, 2014, Fig. 1-5)

  • Forcing (Causes of Climate Change):

  • Tectonic processes (>10⁶ years) – CO₂ release, ocean circulation, landmass shifts.

  • Orbital changes (10⁴-10⁵ years) – Milankovitch cycles.

  • Solar radiation strength (10¹ years) – Variations in sunlight.

  • Anthropogenic forcing – Greenhouse gases and land surface alterations.

• Climate System Components:

  • The atmosphere, ocean, ice, land surface, vegetation – all interact dynamically.

• Feedback Loops & Key Processes:

  • Greenhouse effect: CO₂, CH₄, and H₂O trap heat.

  • Ocean circulation: Upwelling, deep water formation, carbon cycling.

  • Weathering & CO₂ cycling: Rocks remove CO₂; volcanic activity adds it.

  • Hydrological cycle: Evaporation, precipitation, and river runoff affect climate.

Climate system: ocean, atmosphere, ice, land surface and vegetation 

Climate Changes:

causes = forcing 

• tectonic processes >106 years 

• orbital changes 104-105 years

• solar radiation- strength of sun 101 years

• anthropogenic forcing-  alterations of land surface and addition of greenhouse gases

Effect = response = climate change

Ruddiman, 2014, Fig. 1-5

• Main Components

  • External Forcing (Causes):

    • Plate Tectonics → Influences CO₂ release, ocean circulation, and landmass positioning.

    • Earth’s Orbit → Affects solar radiation through Milankovitch cycles.

    • Sun’s Strength → Impacts global temperature via changes in solar radiation.

  • Climate System (Internal Interactions):

    • Includes atmosphere, ocean, ice, land surface, and vegetation.

    • These elements interact dynamically, influencing climate conditions.

  • Climate Variation (Internal Responses):

    • The changes in the atmosphere, ice, vegetation, ocean, and land surface are interconnected.

    • Feedback loops (e.g., ice-albedo effect, carbon cycle) play a critical role.

  • Key Processes Illustrated

    • Greenhouse Effect: CO₂, CH₄, and H₂O trap heat.

    • Ocean Circulation: Upwelling, deep water formation, and carbon cycling.

    • Weathering & CO₂ Cycling: Rock weathering removes CO₂, while volcanic activity adds it.

    • Hydrological Cycle: Evaporation, precipitation, and river runoff affect climate.