Phase Diagram for Water

Hydrogen Bonding in Water

Transfer Processes and Storage (Reservoirs)

Rate of Addition or Removal Residence Time Time to replace a substance in a reservoir, or average length of time a substance exists in a reservoir Total Amount Rate of Addition or Removal Water in atm. = 11 days Water on land = 1 year Water in oceans = 3500 years

Importance of Water Cycle to the Earth System Transfers heat Sea level change Greenhouse gas Global warming will affect it Renewable resource; energy source Weathering and erosion agent Interacts with the Carbon Cycle

Energy Absorbed and Released During Phase Changes of Water

Difference in Heating of Land and Ocean

Summer Winter

A True Color Picture of Earth

amount size

Sea level also changes due to temperature.

Top Climate-Water Issues Sea-level rise Snow-pack loss Redistribution of water resources Water vapor feedback

Ice Sheet Melting & Sea Level Rise

Rate of Sea Level Rise (Data from IPCC WGI Summary for Policymakers)

Sea-Level Rise and Water Supplies Saltwater contamination of coastal ground-water wells Salinity encroachment on municipal water intakes from rivers Loss of glacial meltwater Coastal States

Composition of Natural Waters

Carbonate Equilibria: CO2 + H2O CH3COOH  H+ + CH3COO- CH2O + O2 => CO2 + H2O CO2 + H2O  H2CO3 H2CO3  H+ + HCO3-

Chemical Weathering Limestones H2CO3 + CaCO3 <==> Ca+2 + 2HCO3- Silicates 2H2CO3 + NaAlSi3O8 ==> Na+ + 2HCO3- + clay minerals 2H2CO3 + CaAl2Si2O8 ==> Ca+2 + 2HCO3- What happens to CO2 during chemical weathering? Role of water? pH of river water? Seawater?

Chemical Weathering

Chemical Composition of Seawater Six major constituents Two anions - Cl-, SO4= Four cations - Na+, Mg+, Ca+2, K+ pH is buffered by CO2 - CaCO3 system

Rate of Addition or Removal Residence Time Time to replace a substance in a reservoir, or average length of time a substance exists in a reservoir Total Amount Rate of Addition or Removal

Sources of Sea Salt Weathering of continents Volcanic eruptions Hydrothermal vents

Oxygen Concentration Solubility depends on T and Salinity Warm, saline water holds less O2 Oxygen consumption in water column Respiration by animals Mixing rate of oceans Sluggish mixing - low rate of O2 replenishment

Carbon Dioxide Concentration Solubility depends on T and S CO2 is released by animals Mixing rate of oceans Affects pH of seawater (What is its pH?) Similar to concentration profiles of nutrients (PO4-3, NO3-)

X

CO2 in Seawater pH - function of dissolved CO2 Reacts with water to produce carbonic acid, which releases H+ ions CO2 + H2O  H2CO3  H+ + HCO3- H+ + CO3-2 H2CO3 is carbonic acid, HCO3- is the bicarbonate ion and CO3-2 is the carbonate ion

CO2 in Seawater Carbonate system - buffers against large shifts in pH Carbonates dissolve in deep water Higher CO2 makes the water less alkaline (pH ≈ 7.8) Warm, shallow water has less dissolved CO2 More alkaline than deep water (pH ≈ 8.2) Carbonate sediments are abundant

Carbonate System

Precipitation of CaCO3 ---- HCO3- + OH- => CO3= + H2O

Calcite (or Calcium Carbonate) Compensation Depth (CCD) CaCO3 dissolves in deeper water due to higher CO2 content in deep water Deepest sediments have little or no CaCO3 CCD is deeper (less dissolution) in the Atlantic Ocean than in the Pacific Why?

The Carbonate System

Changes in the CCD for the Past 100 m.y.