Chapter 4 Section 2

Salt Water Composition of seawater most salts present in seawater are present in their ionic form 6 ions make up 99% of dissolved salts in the ocean: sodium (Na+) magnesium (Mg2+) calcium (Ca2+) potassium (K+) chloride (Cl-) sulfate (SO42-) trace elements - present in concentrations of less than 1 part per million

Table 4-2 Major Ions In Seawater.

Salt Water Salinity seawater = 3.5% salt, 96.5% water expressed as in g per kg water or parts per thousand (ppt) salinity of surface water varies as a result of evaporation, precipitation, freezing, thawing, and freshwater runoff from land between 10o N-10o S of equator = low salinity (due to heavy rainfall) areas around 30o N and 30o S = high salinity (evaporation > precipitation) from 50o = low salinity (heavy rainfall) poles = high salinity (freezing – removes water from sea)

Figure 4-5 Ocean Salinity.

Salt Water Cycling of sea salts sea salt originally from earth’s crust ocean composition has remained the same due to balance between addition through runoff & removal salts removed in many ways: form insoluble complexes that precipitate to ocean floor depositing on land by sea spray evaporites (salt deposits) concentration in tissues of organisms harvested for food Adsorption - process of ions sticking to surface of fine particles, which sink and are trapped in sediments

Figure 4-6 Sea Salt Cycling.

Hydrogen sulfide (H2S) Chlorine (Cl2) Sulfur Chloride (Cl–) Precipitation Chloride (Cl–) Sulfate (SO42–) Hydrogen sulfide (H2S) Chlorine (Cl2) Volcano Sulfur Sea spray removes salts Salts removed when organisms are caught for food River discharge Carbonate (CO32–) Calcium (Ca2+) Sulfate (SO42–) Sodium (Na+) Magnesium (Mg2+) Calcium (Ca2+) Magnesium (Mg2+) Potassium (K+) Rock on the seafloor Clay particles adsorb Organisms die Bottom sediments Precipitation Stepped Art Fig. 4-6, p. 75

Salt Water Gases in seawater gases from biological processes oxygen is a by-product of photosynthesis release of CO2 from respiration oxygen-minimum zone – located just below sunlit surface waters solubility of gases in seawater seawater has more O and CO2 but less N than the atmosphere relative solubility in seawater: CO2 > O > N affected by temperature, salinity and pressure

Table 4-3 Gases Found in Seawater

Figure 4-7 (a) Gases In Seawater.

Salt Water role of bicarbonate as a buffer bicarbonate formed from the solution of CO2 buffer - a substance that can maintain the pH of a solution at a relatively constant point bicarbonate’s buffering action helps maintain the pH of seawater at a constant value, providing a stable environment for marine organisms

Figure 4-7 (b) Gases In Seawater.

Ocean Heating and Cooling Earth’s energy budget energy input sun’s radiant energy heats earth’s surface spherical shape + presence of the atmosphere cause the amount of radiant energy reaching earth’s surface to decrease with increasing latitude

Figure 4-8 Distribution of Solar Energy.

Greater angle Less solar energy per unit area Tropic of Cancer Right angle More solar energy per unit area Equator Tropic of Capricorn Greater angle Less solar energy per unit area Stepped Art Fig. 4-8, p. 77

Ocean Heating and Cooling Earth’s energy budget energy output excess energy absorbed by the earth is transferred to the atmosphere by evaporation and radiation accumulation of greenhouse gases (CO2, methane, chlorofluorocarbons (CFC’s)) can prevent heat energy from radiating back to space

Figure 4-9 The Earth’s Energy Budget.

by clouds Absorbed by atmosphere and clouds Radiation from atmosphere Reflected by ground by clouds Absorbed by atmosphere and clouds Radiation from atmosphere Absorbed by rock, soil, and water on the surface Convection and conduction to the atmosphere Scattered and deflected by atmosphere Heat transferred via evaporation Radiation from earth Radiation to atmosphere and clouds Stepped Art Fig. 4-9, p. 78

Ocean Heating and Cooling Sea temperature temperature varies daily and seasonally affected by energy absorption at the surface, loss by evaporation, transfer by currents, warming/cooling of atmosphere, heat loss through radiation seasonal variations in the amount of solar radiation reaching the earth, occur especially between 40o and 60o N and S because angle of sun’s rays change dramatically at these latitudes seasonally

Figure 4-10 Average Surface Temperatures Of The World Ocean.