Properties of Sea Water Flashcards
What makes water special?
- Physical propety: water has great heat capacity
- Chemical property: very good solvent
- Implications for Earth and ocean, directly affect chemitsry of seawater and how the ocean moderates Earth’s temperature
Other important aspect of water: density, light, pH, gases
- Density changes as a result of chanegs in temp and changes in salinity –> ocean circulation
- Light does not travel far in the ocean, but sound does –> life in the ocean
- the pH of seawater is relatively constant, 8.2 –> life in the ocean
- gases (oxygen, carbon dioxide) dissolve easily in sea water –> climate
Thermostatic properties
Properties that act to moderate changes in temp
* high heat capacity - amount of heat needed to produce a unity change in temp
* high latent heat - amount of heat that can be absorbed when it changes state
* strong thermal inertia - ability to hold onto stored energy
How to change states of matter?
Change in heat/energy
Temperature
The property of the water that changes as heat is added or removed
Heat
A measure of the amount of energy contained in a volume of water
Heat capcity
The amount of energy (or heat) required to raise the temperature of 1 g of a substance by 1 degree C (measured in calories per gram per degree)
Latent heat
- Energy is being added, but the temperature does not chaneg (the energy is “hidden away” in the water)
- Certian amount of heat need to be added to chaneg temp of water. releases or absorbed heat during phase change
How to exchange energu between low and high latitudes?
Evaporation and condensation
Water density
Mass / volume
kg / m^3 or g / cm^3 or g / mL
Controlled by temperature and salinity (and pressure)
Desnity of pure freshwater and seatwater
1000 kg / m^3 = 1 g / m^3
1022 to 1030 kg / m^3
Why does water become less dense as it freezes?
- Water is packed less desnly is ice
- Change in density comes from change in volume
Effect of salinity on density
Salinity
The total amount of dissolved inorganic solids in the water
* Average salinity is 3.5% = 35 ppt
* Open ocean 33-38%
How does salinity impact ocean
- Increases the density
- Lowers the freezing point of water from 0 C to -1.9 C
- Increases pH of water from 7 to 8.1
Salinity ranges in ocean
Processes affecting salinity
Why is ocean salty?
- Ocean cotnains erosian products, transported into ocean
- by rivers, deopsition from volcanoes or hydrothermal vents
- Sodium from land, chloride from hydrothermal
- Balanced by slow removal of sediemtns
Why does salinity not change over millions of years?
- The ocean is in steady steady state: what goes in must come out
- Salt is added at same rate it is removed
Principle of constant proportions
- Ratio of major salts ions in sea water are cosntant (regardless of salinity)
- If you measure the concentration of one iron you can estimate the others
- Elements that follow this principle are called conservative elements (do not change with water depth)
Non-conservative elements
- Elements involved in biological processes vary greatly in space and time
- Nutrients are often depleted in the surface due to comsuption by phytoplankton, and high at depth due to recycyling
- Phosphate and nitrate
Residence time
amount of element in the ocean / rate the element is added or removed
* Average length of time a substance remainds dissolved in water
* Major salt ions (Na, Cl) –> high concentration, long residence time
* Nutrients (Fe, P, N) –> low concentration, short residence time
Oceans pH buffering system
- pH of seawater is well buffered, meaning it does not vary much (7.6 to 8.3 = slightly alkaline)
- Too much CO2 dissolution will exceed the buffering capacity –> ocean acidification
- Biological systems need a stable environment to do their biology
ph with ocean depth
Calcium Carbonate Compensation Depth (CCD)
- Deep water is more acidic
- Calcium carbonate is in the surface, but dissolves below the CCD
- Calcium carbonate sediments only accumulate in relatively shallow water “marine snow”
- Below the CCD water is relatively corrosive (low pH) and calcium carbonate dissolves
Gases in the ocean
- Gases like oxygen, nitrogen, and carbon dioxide are continuously exchanged between the atmosphere and the ocean, but their relative proportions differ
- Biological activity in the ocean uses up oxygen and carbon dioxide
Distribution of gases by depth in ocean (O2 and CO2)
- Oxygen concentrations higher in surface layer than in atmosphere (photosynthesis)
- Carbon dioxide concentrations in the deep water increases because of respiration
Why is the ocean blue?
- Red is absorbed fastest
Photic zone
Sunlit surface of the ocean
