Phase Diagram for Water

Hydrogen Bonding in Water

Transfer Processes and Storage (Reservoirs)

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 heatSea level changeGreenhouse gasGlobal warming will affect itRenewable resource; energy sourceWeathering 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 meltwaterCoastal States

Composition of Natural Waters

Carbonate Equilibria:CO2 + H2O

•CH3COOH H+ + CH3COO-

•CH2O + O2 => CO2 + H2O

•CO2 + H2O H2CO3

•H2CO3 H+ + HCO3-

Chemical WeatheringLimestones

H2CO3 + CaCO3 <==> Ca+2 + 2HCO3-

Silicates

2H2CO3 + NaAlSi3O8 ==> Na+ + 2HCO3-

+ clay minerals

2H2CO3 + CaAl2Si2O8 ==> Ca+2 + 2HCO3-

+ clay mineralsWhat 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

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 continentsVolcanic eruptionsHydrothermal vents

Oxygen Concentration

Solubility depends on T and SalinityWarm, saline water holds less O2

Oxygen consumption in water columnRespiration by animals

Mixing rate of oceansSluggish mixing - low rate of O2 replenishment

Carbon Dioxide Concentration

Solubility depends on T and SCO2 is released by animalsMixing rate of oceansAffects pH of seawater (What is its pH?)Similar to concentration profiles of

nutrients (PO4-3, NO3

-)

X

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

CO2 in Seawater

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.