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.
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.
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 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.
Temperature variation is greater over land than over oceans.
Oceans absorb and store heat more effectively.
Tropical areas have less seasonal temperature variation.
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.